Gusty thunderstorms put on quite a lightning show as they hopscotched across portions of the Chicago area Friday night. The storms erupted within humid air paralleling an unusually vigorous jet stream which roared from Texas through the Great Lakes and into Canada--and continues to do so Saturday. As Friday and Friday night's storms bubbled aloft and were picked up by these powerhouse high-altitude winds, their forward motion soared to 70 mph as they raced across IIllinois, Missouri and eastern Iowa.
That jet stream is to play a key role in delivering the Chicago area's next rain Saturday night--some of it again potentially thundery. The jet is to pick up a new disturbance over eastern Texas Saturday and send it speeding toward the Midwest. It's a development which has the clock ticking on Saturday's sunshine. Northeastbound clouds expected to invade Chicago's airspace well ahead of the rainy system should begin filtering sunshine even before Saturday evening arrives. The new round of showers and thunderstorms is likely to get underway later Saturday night.
While the axis of the heaviest rainfall is to fall south of Chicago, computer model estimates of rainfall likely to fall with the system in the Chicago area range from a half inch to an inch or more--not all bad news after coming off a drier-than-normal April. That's especially true because much of the rain is to fall at night and not disrupt the myriad outdoor activities so much a part of of the weekend here.
Books close on the warmest April in 33 years; one of the warmest in 140 years of records
April's level of warmth was quite remarkable. The month's 54.6-degree average was 6.6 degrees above normal (more than 7 degrees milder than a year ago)--warm enough to tie as the third-warmest April in 140 years of official Chicago weather records. It was the warmest April in 33 years since 1977.
Summers which have followed the 10 warmest April have produced near normal 90-degree tallies
Not one of the past four summers has come even close to producing the typical number of 90s. That's been disappointing to the area's hot weather enthusiasts. A summer with the normal number of 90-degree days would appear warm by comparison. That's what may be on the way if the upcoming warm season follows historic precedent in the wake of exceptionally warm Aprils like the one just concluded.
The average number of 90s here over the years has been 23 at Midway Airport and 17 at O'Hare Airport. Summers which have followed the 10 warmest Aprils have gone on to produce an average of 25 days at or above 90--close to the normal tally. Of course, many factors contribute to a summer's temperature trend, but it will be interesting to monitor.
Dear Tom,
At Easter, our dinner-table conversation centered on the difference between lightning and heat lightning. Can you clarify?
--The Taylor-Gradle families
Dear Taylor-Gradle families,
Heat lightning is nothing more than regular lightning generated from a thunderstorm so distant that the thunder cannot be heard and often the parent cumulonimbus cloud can't be seen. With summer thunderstorms routinely building to more than 50,000 feet in height, lightning emanating from the tops of these storms can be visible for more than 100 miles and the sound of thunder rarely travels more than 15 to 20 miles. The term "heat lightning" came into use because the distant lightning was frequently observed on hot, humid summer nights when people remained outdoors well after dark.
High winds are likely to send dust airborne again over parts of the area while temperatures surge into the 80s Friday---the fifth time that's happened in 2010. The month is headed for a midnight close as one of the 5 warmest Aprils since records began here 140 years ago. And, with 82 predicted Friday, it may well be the first time on record an April has opened and closed with high temperatures in the 80s. The peak reading April 1 was 83 degrees.
Warmth of this magnitude doesn't easily occur this time of the year without a good deal of wind. That was certainly the case Thursday as the city's official O'Hare high missed 80 by just a degree in the midst of howling winds. From one corner of the metro area to another, gusts approached or topped 50 mph. Long-time weather observer Wally Gullang in west suburban Huntley, Illinois e-mailed to report a hand-held wind device he carried as he worked in his yard clocked a wind gust of 56 mph.
Powerful wind gusts top 50 mph Thursday, send dust airborne
While the Harrison-Dever Crib walked away with the Chicago area's strongest reported individual gust of 59 mph, the 53 mph velocity clocked at Midway Airport ranks as that site's strongest in the 10 months since last June. Other metro area gusts included 55 mph at Glenview , 52 mph at Rockford and Portage, Indiana and 51 mph in Aurora. Winds topped out at 49 mph in DeKalb and Naperville and 48 mph at Kankakee and Pontiac.
The warm air, expected to propel Thursday highs into the 80s a second consecutive day, dovetails with April 2010's overall temperature trend----very mild. Daily temperatures this month have averaged above normal 73 percent of the time and the month's 54.0 degrees qualifies as the 5th warmest of the past 140 years. The month is to end Friday night 7.4-degrees above a year ago and more 6-degrees above the long term 140 year average.
Drier than normal weather across the Great Lakes drainage basin---the region which feeds water into the massive bodies of water---continues to drive water levels lower. Lake Michigan has sunk 6 inches below this time a year ago, according to U.S. Army Corps of Engineers.
Storm to flare west then charge eastward
The Storm Prediction Center places Chicago at the edge of a "slight risk" area for thunderstorms through Friday night. Powerful thunderstorms, with clouds which punched 48,000 ft. into the atmosphere, unleashed a barrage of golf-ball size hail across Kansas, Nebraska and Iowa late Thursday. Additional severe storm development is anticipated to Chicago's west Friday. The wildcard Friday night is the degree to which these storms hold together beyond midnight when they roll into Chicago. Atmospheric energy levels here will be at borderline severe levels at that time according to a number of computer projections. Though the storms may roll into the area in a weakening state, the strongest among them may still capable of powerful winds and hail.
The storms break to allow warm, rain-free weather Saturday---but not for long. A vigorous northeast-bound disturbance beneath a 140 mph jet stream threatens new rains and possible thunderstorms by later Saturday night into Sunday morning.
Same southerly wind regime behind gales here drives expanding oil spill onto the Gulf Coast
The southern extension of the powerful southerly wind band which raked the Midwest Thursday and continues Friday pushed the ever-expanding oil slick over the Gulf of Mexico within miles of the shoreline late Thursday. Attempts to halt the flow of oil failed Thursday though good weather in recent days allowed the application of 50,000 gallons of dispersant and a limited control burn of patches of oil to take place. Strong south to southeast winds threaten to push the oil into the coast.
Dear Tom,
What is the United States' strongest earthquake?
--Thomas McBrennen
Dear Thomas
The Good Friday earthquake in Alaska in 1964 was the most powerful
recorded U.S. quake (note that earthquakes are geological phenomena,
not atmospheric; they do not affect the weather).
The Alaskan quake lasted nearly 7 minutes and released 200,000 megatons
of energy. Anchorage suffered massive damage. Portions of the city sank
20 feet, and 130 acres of suburban Turn again Heights slid into the sea.
The coastal town of Valdez, 120 miles to the east, was devastated by a
combination of the earthquake, landslides and a tsunami.
Miraculously, only one death resulted
Winds are roaring across the Chicago area Thursday! Some peak gusts through 1PM include: 49 mph at Aurora; 47 Pontiac; 46 Sugar Grove; 43 Rockford; 41 mph Glenview, Naperville, Lombard, and Hillside; 40 mph DeKalb, Franfort and Kankakee; 39 Harwood Heights; 38 Hinsdale, East Chicago, West Chicago, Chicago's O'Hare International and at New Lennox. A wind advisory continues in effect across the metro area and all of northern Illinois and northwest Indiana through 7 pm Thursday evening.
This wind field extends 1400 miles...all the way from the Gulf of Mexico, where it's pushing the mammoth oil slick so much in the news the past week, toward the Gulf Coast.....northward to the Lake Superior shoreline. It's the same band of winds responsible for 80+ mph gusts on the front range of the Rockies in eastern Colorado and 50+ mph gusts in Nebraska and the Dakotas Wednesday.The powerful winds are to continue in Chicago through Thursday night and Friday, ultimately delivering the area its most humid air of the year with low to mid 60 dew points Friday. (The previous highest dew point this year was 61-degrees during the 80-degree spell earlier this month.) It's that moisture which is to fuel thunderstorm development later Friday or Friday night.
My meteorological colleague and former WGN weather intern, Mike Tannura, now of T-Storm Weather, LLC, e-mails that Illinois' average statewide April temperature is on track to finish the warmest on record! Temp records go back to 1895.
In Chicago, Thursday's warmth is to include the Chicago area's first 70+ high temperature in two weeks. An 80-degree high Friday would be the fifth 80+ of 2010.
Storms and a severe weather threat continue to appear possible here or nearby Friday night. We'll have more on the WGN News 5 & 9!
Chicago is in for vigorous warming and a multi-day rendezvous with
strong winds which may top 35 mph later Thursday and Thursday night and
40 mph at times Friday. An eastward shift in the band of southerly
winds, which blasted sections of the Plains Wednesday with powerful
gusts even before late day thunderstorms erupted is behind the forecast
of powerful winds in Chicago.
The howling winds hurled dust through the air in sections of the
Plains. Non-thunderstorms gusts hit 87 mph at Monarch, Colorado
Wednesday at the same time 54 mph winds whipped Selby, South Dakota.
North Platte, Omaha and Scottsbluff---each in Nebraska---dealt with 46
mph gusts.
Year's moistest air hits Friday, potentially fueling strong t-storms
Severe weather threatens the western Midwest Thursday and is likely to
re-erupt within a 1,400 mile corridor from the Gulf of Mexico north to
Lake Superior Friday and Friday night---a zone which includes the
Chicago area. The year's most humid air to date is to sweep into the
Heartland. Dew points, which reflect the atmosphere's moisture
content, are expected to surge into the mid 60s in Chicago Friday. That
will lend the air a warm "feel"---but the moisture is also likely to
fuel powerful thunderstorm development.
The storms may not reach Chicago proper until late in the day or Friday
night. But the cumulonimbus clouds (thunderheads) responsible for the
windy, thundery downpours these storms might unleash, are likely to
bubble up into a 100+ mph jet stream expected to steer them from the
south/southwest toward the north/northeast at a high rate of speed.
This raises the potential for these storms to be high wind producers.
What's more, computer models are predicting much larger than normal
vertical temperature declines. This will encourage warm air near the
surface to rise and cool, rotating as it does. Tornadoes often develop
in such an environment.
Chicago's rendezvous with severe weather: Late Friday and/or Friday night
The best thinking at the moment is several scattered, fast-moving (and
therefore gusty) thunderstorms may pop at a few locations in Friday's
near 80-degree warmth. But, it's Friday night which could see the best
organized cluster or line of storms sweep the area. The evolving
weather situation seems highly likely to necessitate severe weather
watches across parts of Midwest.
Huge swath of south winds also likely to push monster Gulf oil slick into the coast
There are ominous signs the same band of southerly winds expected to
boost temperatures in Chicago and across the Midwest will blow over an
expanding oil slick in the Gulf of Mexico, forcing it on shore in the
days to come. The oil is bubbling from 5,000 feet below the ocean
surface where an oil rig burned and collapsed last week in the Gulf of
Mexico southeast of Louisiana. The disaster resulted in the deaths of
11 workers.
Weather forecasts for the region are for the north winds which have
held the oil offshore to shift southeasterly and increase in coming
days. The strengthening winds are likely to produce waves which build
at times to 7 to 12 feet---bad news for efforts to contain the spill.
Dear Tom,
Many people said last summer was the worst they could remember, but I recall a summer about 15 or 20 years ago when we got into a repeating pattern of five beautiful days followed by two rainy days (Saturday and Sunday). Is my memory correct?
--Michael Levine
Dear Michael,
Your memory is reasonably correct, but we had to allow you some wiggle room. We examined the summers from 1985 through 1995, searching for patterns of dry workweeks (Monday through Friday) and rainy weekends.
The summer of 1989 featured five consecutive weekends with rain, beginning with July 22-23, but the intervening Monday-Friday periods were not exclusively dry. The summer of 1990 was similar. It brought six consecutive wet weekends beginning with July 14-15, but plenty of rain also fell between the weekends.
Temperatures soared across the Plains Tuesday, jumping in portions of
Montana, Wyoming and the western Dakotas more than 20-degrees above
readings a day earlier. It's a turn of events which clearly indicates
where Chicago's temperatures are headed. The rebound in coming days
will take temperatures here more than 45-degrees above the 20s and 30s
responsible for Wednesday morning's frost patches in parts of the metro
area.
Readings Wednesday afternoon jump 10-degrees above
Tuesday's 51-degree high, riding to 60-degrees. But even more
significant warming follows when powerful southerly winds, expected to
become stacked through the atmosphere from the ground tens of thousands
of feet aloft into the atmosphere---ultimately reaching the jet stream
level. The result will be 70s Thursday for the first time in two weeks
and a Friday high which could reach 80-degrees. Such a high would mark
the fifth 80-degree temperature of 2010.
The big warm-up comes
on the heels of Tuesday's chilly northeast winds which arrived in the
city after a 260 mile trek over Lake Michigan's coldest mid-lake
waters. There, water temperatures hover near 40-degrees.
The
collapse of those northeast winds assures the lake cooling which
transpires Wednesday won't be as strong nor will it cover the terrain
Tuesday's organized northeast flow did.
Incoming warmth to arrive next 2 days with one of 2010's most humid air masses yet
With
winds Thursday night and Friday predicted to blow from the south at
nearly 60 mph just a mile above the ground and more than 100 mph two
miles aloft, the flow takes on the role of a giant atmospheric conveyor
belt. Moisture riding this conveyor north from the Gulf of Mexico will
lead to surging dew points in Chicago and a more humid feel to the air.
Dew points provide a measure of atmospheric moisture and are expected
to increase from the mid 20s Tuesday evening to the low 60s Friday
afternoon---the highest to date this year. Adding moisture to air makes
it feel warmer and the predicted influx of Gulf moisture on the
strengthening southerly winds predicted in coming days will be no
exception.
Vertical stacking of strong south winds suggests suggest late week thunderstorms could be high wind producers
Increased
moisture suggest extensive cloudiness is likely Friday. A steep
vertical temperature decline will encourage air to rise and form
scattered showers and perhaps several thunderstorm during the day. But
at night, as a front swings into the area, storm coverage may grow
better organized. Exceptionally strong winds through the atmosphere
will provide an environment in which any thunderstorms which bubble
aloft become "fast-movers." Rapidly-moving thunderstorms produce
powerful gusts, so this will be a situation to monitor. Atmospheric
energy levels predicted Friday night will be elevated and increase the
risk a more organized band or line of thunderstorms capable of strong
wind production will come together.
Dear Tom,
On May 8, 2009, southern Illinois was hit by a derecho, but some called it an inland hurricane. Can you explain what actually happened.
--Tracy Golden, Carbondale
Dear Tracy,
On May 8, 2009, a fast-moving long-lasting line of thunderstorms known as a derecho ravaged southern Illinois. This massive thunderstorm complex was streaking east at speeds approaching 70 mph and packing peak winds in excess of 100 mph. Bill Davis, head of the National Weather Service in Springfield, Mo., commented that the storm was like an "inland hurricane" because of its size and its hurricane-force winds and that terminology spread like wildfire. In Spanish, derecho means "direct" or "straight" in reference to the storm's straight-line winds as opposed to the rotary winds of a tornado. Derechos can last more than 24 hours and generate damage paths in excess of 1,000 miles.
It's been the warmest April here in 33 years (since 1977) and the 4th warmest of the 140 on the books since 1871. More than two-thirds (67 percent) of the month's days have posted temperature surpluses. April's 54.3-degree average temperature is an eye-catching 8-degrees ahead of a year ago and 7-degrees above the long term (140-year) average. All this makes the chilly air Tuesday which has hijacked the recent warmth more than a bit jarring---despite an abundance of sunshine.
Northerly winds are uniquely aligned with the coldest waters Lake Michigan. Because of the added time a north wind is over the water, it's ability to transfer that chill ashore is impressive. An analysis of satellite-derived lake temperatures suggests the path Tuesday's surface winds are following into Chicago assures a nearly 270 mile trek over lake waters hovering at just 40-degrees.
Frost a threat as winds die Tuesday night
Winds are expected to ease dramatically Tuesday night. Clear skies and a supply of remarkably dry air suggest overnight readings will be dropping off dramatically boosting the potential for frost formation.
70s Thursday would be Chicago's first in 2 weeks
Not since April 15, when the temperature last made it above 70-degrees (ultimately peaking at 82-degrees) has 70-degree warmth reached the city. That is to change later this week as strong southerly winds allow warming to reach the city.
Progress with planting on area farms has been impressive
USDA, in its weekly report Monday, indicates that statewide, 73 percent of the corn and 91 percent of the oats farmers intend to grow in 2010 has been planted---a pace which dramatically outstrips last year's. Farmers in sections of the Chicago area have outstripped the statewide average having planted 90 percent of this area's corn---a welcome change from last year's rain-plagued planting season.
80-degree warmth in coming month just shy of a certainty; even a fair potential for 90-degrees
The potential for warm weather rises at an accelerating pace this time of year. A review of weather records dating back to 1928 at Midway Airport offer guidance on the likelihood of the following warm temperatures occurring between now and May 31:
70-degrees or higher: 100 percent chance
75+:: 100 percent
80+: 96 percent
85+: 88 percent
90+: 49 percent
95+ 4 percent
100+: 1 percent
Dear Tom,
Severe weather spotters are instructed to look for
rotation in suspected funnel clouds and tornadoes, but I recently saw a
video of funnel clouds with no rotation developing toward the ground.
Is there an explanation?
--Daniel Heyl
Dear Daniel,
"If it spins, turn it in" is the mantra for severe weather spotters because a tornado is defined as "a violently rotating column of air extending from the base of a thunderstorm to the ground."
At ground level, air always spirals inward toward the tornado, usually
in a counterclockwise rotation, but occasionally clockwise. Thus,
rotation always exists in a tornado.
However, it can be different
above the surface layer. There, air usually spirals upward through the
trunk of the tornado -- usually, but not always. On rare occasions, the
primary motion is practically straight upward, with little rotation.
The low pressure system that triggered 55 tornado and 159 severe weather reports mainly across the southeastern U.S. Saturday, and dumped nearly four inches of rain over west-central Illinois (3.87 inches reported near New Windsor in Henry county) and widely varying amounts up to an inch in the Chicago area moved east Sunday. Severe thunderstorm Watches were up late Sunday afternoon from north central Pennsylvania to central Virginia (mostly one-inch hail reports) and in central Florida (damaging winds downed trees and power lines). A tornado was reported in South Carolina.
Chicago cooled by winds off Lake Michigan
North to northeast flow off the 40-degree waters of Lake Michigan will cool the Chicago metro area and northwestern Indiana the next couple days. However, as the upper air pattern evolves, southerly flow should return to the Midwest mid-week. Ahead of an approaching cold front, temperatures are likely to peak in the mid 70s here Thursday with a line of thunderstorms moving into the area just ahead of the front later Thursday night or Friday.
Dear Tom,
The great "dinosaur extinction" took place 65 million years ago. Were there other extinctions?
-- Pam Roop
Dear Pam,
The astonishing variety of life on Earth has suffered many setbacks -- what biodiversity scientists refer to as "extinctions."
Single-celled organisms appeared in the seas about 4 billion years ago. The first of several known extinctions occurred 440 million years ago, when many marine organisms disappeared; another eliminated 70 percent of marine animal species 370 million years ago; another 250 million years ago wiped out 90 percent of animal species, and again 210 million years ago. The dinosaur extinction followed 65 million years ago.
A final extinction began about 20,000 years ago and continues today, perhaps resulting from a combination of global climate change, human hunting and human environmental disruption.
Severe storms and killer tornadoes raked portions of the Gulf Coast states north to the Ohio River Saturday evening. Hardest hit was Mississippi with unofficial reports of 5 deaths and multiple injuries. By 9 p.m. 49 tornadoes had been reported in 5 states. Low pressure centered over southeastern Missouri was moving northeast into Illinois producing heavy rains. The associated cold front extending south out of the low center along the Mississippi River to the Gulf of Mexico was sweeping east, triggering lines of supercell thunderstorms. Eight states were under Tornado Watches, some in effect until 2AM Sunday morning. Parts of the southern two thirds of Illinois and Indiana were under a tornado Watch as of 9:30PM.
Midweek warm up
As the area of low pressure moves well to the east, southerly flow will return to Illinois midweek. Temperatures in the 70s are expected by Thursday with another band of showers and thunderstorms likely Friday.
Dear Tom,
I live on the 28th floor of a high-rise on North Sheridan Road in Chicago and I have an unimpeded view to the west. How far west am I seeing? There are no landmarks to fix upon. I'm sure I'm not high enough for the Earth's curvature to make a difference.
--Ann Lee, Chicago
Dear Ann,
The curvature of the Earth does make a difference. Because the surface of the Earth is curved and slopes away from you, the higher your viewing point, the farther you can see to the horizon. A "horizon formula" exists and the calculation is as follows: To find the distance to your horizon in miles, take the square root of the height of your view, in feet, and multiply by 1.224. Your answer will be the number of miles to the horizon from your vantage point. Let's assume you are 280 feet above the street. The square root of 280 is 16.7332, which, when multiplied by 1.224, yields about 20.5 miles.
Chicago's driest spring in five years is about to get a lot wetter. Rainfall--some of it thundery--sweeps across the area in waves this weekend--pausing or, at minimum, diminishing to lighter, more scattered showers for a time mid and late Saturday morning into afternoon, only to intensify again as a new round of potentially active thunderstorms--a number possibly accompanied by downpours--sweeps in from the south later this afternoon.
The atmosphere is predicted to warm Saturday at the same time spring's most humid air--with 60-plus degree dew points downstate--moves up and over a northbound warm front which is approaching Chicago, but likely to stall just short of the city. This sets up a situation where east winds off chilly Lake Michigan cool the immediate lakeshore to the 50s, possibly producing fog in the process, while warmer, more humid air reaches the southern suburbs.
Energy calculations, which give meteorologists a measure of the atmosphere's ability to produce vigorous thunderstorms, plus the expectation that powerful jet stream winds will reach this area's airspace later today, are among the indicators which suggest vigorous late day and nighttime thunderstorm development is likely to occur. NOAA's Storm Prediction Center indicates portions of the metro area are at risk for severe weather.
Not since October has the Chicago area been doused by a multi-day rain of this weekend's predicted intensity. Spring rains have amounted to half those which fell a year ago--3.87" through late Friday versus 7.66" last spring. The dry weather has allowed many area farmers, who couldn't even get into their fields until late May and June last year, to complete the planting of their corn crop early in anticipation of the arrival of the current storms welcome but, for those with outdoor plans, poorly timed rains.
An average of 30 weekend rainfall forecasts from a suite of computer models suggests O'Hare could see something close to 2.20" of rain. But precipitation doesn't fall uniformly, especially when thunderstorms are involved. Amounts can vary widely. A look at the range in individual model rain estimates offers a guide for bracketing the spread in rainfall totals which may occur with the current storm across the greater Chicago area. Predicted amounts vary from as little as 0.92" off one model to as much as 3.18" off another.
Thundery downpours to pick up later today and overnight; chilly, windy-driven rain due Sunday
The predicted increase in thunderstorm coverage and intensity later Saturday and Saturday night occurs as the surface storm center enters Illinois and deepens during its trek from Missouri to southern Lake Michigan by Sunday morning. This coincides with the arrival of a powerful pocket of jet stream-level winds known as a "jet streak." Its features like this which are carefully monitored by severe weather forecasters since they offer important clues on where air is rising--and thus is most likely to produce clouds and precipitation.
Reduced winter snow, dry spring have cut into Lake Michigan water levels
Lake levels, after rising in recent years, are retreating. The past winter's limited snowfall over the upper Midwest and this spring's lack of rain are driving the lake level pullback, says the U.S. Army Corps of Engineers office in Detroit. Lakes Michigan and Huron have dropped 4 inches compared to a this time last year, while Lake Erie has retreated 13 inches and Lake Ontario has fallen an eye-catching 19 inches.
Dear Tom,
Historically some instances of volcanic activity have been responsible for changes in weather due to ash in the atmosphere. With the ongoing eruption of the Eyjafjallajokull volcano, will Europe have a cooler-than-normal summer? Could the U.S. be affected?
--Jeff Schmeckpeper
Dear Jeff,
Because sun-blocking particles following volcanic eruptions are eventually disbursed worldwide, the resulting cooling is a global rather than a local affair. However, the particles must be injected into the stratosphere, the atmospheric layer extending from about 6 to 30 miles aloft. The layer below that, the troposphere, is the layer in which "weather" occurs. Particles injected into the troposphere are washed out of the air by precipitation. To date, ejecta from the Iceland volcano are mainly below 20,000 feet.
Wild spring weather raked sections of the Plains Thursday in association with a powerful spring storm which is headed for Chicago and the Midwest this weekend. Across western Kansas, the Texas Panhandle and eastern Colorado, ten-mile high thunderstorms spawned clusters of tornadoes. There hasn't been a single day which has hosted more reports of tornadoes this year than Thursday. The tally had surged to 31 by late evening----and was still rising.
A large tornado, which spotters indicate may have been accompanied by a "satellite" twister, is reported to have touched down just before 7 pm near Friend, Kansas. Another, described as large, was reported on the ground around 7:30 p.m. near Cee, Texas.
It's only the beginning; additional severe weather ahead in the Heartland
The atmospheric table has been set for additional severe weather Friday and Saturday. With a split in the key jet streams steering North American weather across the continent in place over the Rockies late Thursday---one branch branch heading north into Canada, the other sweeping southeastward around the periphery over a cold pool aloft over the western Plains---spring's latest storm, caught between the two streams---threatens to be an especially slow-mover! It's possible rain could fall here in some form or another into Monday.
The storm behind the eruption of tornadoes and flooding rains west of Chicago Thursday, expands its severe weather-generating capability into Illinois Friday and Friday night. Forecasters warn severe thunderstorms---and in spots tornadoes---may occur as far north as Bloomington and Dixon Friday and Friday night.
The powerhouse large scale storm, due to move from Kansas to Illinois, where it will slow and undergo a period of impressive intensification later Saturday and Saturday night, stands a good chance of bringing the Chicago area its heaviest rains to date this year. Rainfall projections from a suite of computer forecast models put nearly 2 inches down across a good swath of the metro area. Specific rain estimates through Monday from some of these models include a 1.81-inch average projection from the dozen most recent National Weather Service "GFS" (Global Forecast System model) runs, 3.27 inches from the Navy's "NOGAPS" model, 3.08 inches from Environment Canada's "GEM" model and 1.98 inches from the European Center's "ECMWF" mode. All suggest rains are likely to arrive in several comparatively concentrated bursts---the first due later Friday night into Saturday morning (following several scattered Friday afternoon or evening showers), and a second potentially to arrive later Saturday night into Sunday. Rain-free periods are likely in the interim. All the moisture arrives in a spring which has been the driest here in 5 years.
Widespread---or what meteorologists refer to as "synoptic scale" rains---aren't all bad in spring. The absence of such precipitation events in recent weeks has quietly concerned some observers who know that if the critical large-scale rains don't occur in March, April and/or May, summer's increasingly intense sunlight can lead to drought.
31 twister reports late Thursday---and the tally's still rising!
By late evening, 33 reports of twisters had been filed with NOAA's Storm Prediction Center---and the figure continued to rise. The twister outbreak made Thursday the single busiest day in 2010 for U.S. tornadoes yet.
Towering thunderstorms drown eastern Kansas in a month's worth of rain in a single day
The drenching thunderstorms which hit eastern Kansas and western Missouri, produced more rain in a single day than typically falls in the ENTIRE month of April The deluges walloped the Emporia, Kansas area particularly hard. Stretches of some roads area were reported under water. Rainfalls in the region Thursday included 3.60 inches near Melvern, 3.50 inches outside Hartford, 3.35 inches in the Burlington area---all in Kansas--- and 2.36 inches at Pleasant Hill, Missouri.
Despite recent chill, April still running 4th warmest on record
Thursday topped out at 60-degrees in Chicago---a seasonable reading. This month---the warmest April on record here only a week ago--- has slipped to 4th-warmest of the past 140 years. But, it is still running 7.7-degrees above the long term average and well ahead of last year.
Dear Tom,
I keep seeing pictures of lightning with the Iceland volcano. What causes it?
--Charmaine Fortuna, Plainfield, and Peter Gottstein, Chicago
Dear Charmaine and Peter,
Volcanic lightning, while frequently observed, is not fully understood. It appears that volcanic lightning formation is somewhat analogous to thunderstorm lightning --- produced by a separation of positive and negative charges from colliding materials. In thunderstorms, it is the collision of hail and rain, while in a volcano the collision of ash and solid debris particles cause the positive and negative charges to separate. The smaller and lighter negative charges tend to rise while gravity causes the heavier positive charges to fall. When the charge differential is great enough, a static electricity discharge produces the lightning.
The weather of two seasons was draped across the Chicago area on either side of a sharp, southward-drifting back-door cold front Wednesday. The extreme temperature spreads which develop across such front lead many to refer to these jarring thermal demarcations as "pneumonia fronts".
The term was certainly appropriate Wednesday. On one side---to the front's west and south---was short-sleeve, summer-like weather with temperatures in the mid and upper 70s. To the east and north, it felt more like late winter or early spring and jackets were the order of the day. At one point around 3 p.m. Wednesday afternoon, temperatures 75 miles southwest of Chicago at Marseilles surged to 79-degrees---a level at which they lingered much of the afternoon---while north suburban Wilmette shivered in 37 degree air.
West and south suburban locations including De Kalb (68-degrees), Geneva (76), Joliet (72), Kankakee (72), Rockford (72), Aurora (71), Romeoville (70) and Rensselaer, IN (72) also basked in unseasonably mild air. But at precisely the same time, northeast winds produced wind chills as low as the low and mid 30s and thermometer readings no higher than the upper 30s and low 40s in the coolest lakeshore areas---from Grant Park north to the Wisconsin line and beyond.
That chilly air was on the move and its interaction with warmth to the west permitted several spotty showers and even a few isolated thundershowers to bubble up to 34,000 ft. into the atmosphere late in the afternoon into Wednesday evening. The showers quickly weakened as westerly steering winds aloft forced them into the cool air which covered the city and other shoreline locations.
Driest spring here in 5 years to get a lot wetter
Chicago is in the midst of its driest spring in 5 years. This season's 3.86 inches is roughly half the 7.34 inches on the books a year ago. It's the 44th driest spring of the past 140 years and has logged rains 20 percent below the long term average.
Interestingly, the 3.86 inches which has fallen since March 1 equals the exact spring rainfall which had fallen up to this point in 1988---a year which went on to produce a serious drought and more temps above 90 degrees, 47 of them including 7 highs of 100+ degrees than in any year since 1871.
An analysis of precipitation trends in comparably dry springs to date indicates most (9 of 13) have remained drier than normal the remainder of spring. But the pattern offers little insight into the rainfall trend in the June through August meteorological summer season.
All eyes on a big weekend spring storm which could make a dent in the dry spring
The heaviest rains of the 2010 spring season to date---indeed, potentially the heaviest rains since the 1.62 inches which fell April 4-5 this year---appear headed for Chicago this weekend. An influx of warm, moist air likely to be forced up and over a downstate warm-front at the same time powerful upper-level winds arrive, enhancing lift, threaten to produce waves of heavy rainfall Friday night through Saturday night. As much as 1 to 3 inches of rain could fall, according to the 12 most recent rainfall projections off the National Weather Service's "GFS" (Global Forecast System model). Other models---among them the Navy's "NOGAPS" (2.92 inches), the Japanese Meteorological Agency's "JMA" model (1.44) and Environment Canada's "GEM" model (2.24) predict healthy rainfall this weekend.
Severe weather to erupt across the Plains Thursday in a season with only a quarter of last year's twisters to date
The lack of severe weather this year across the U.S. this has been stunning---but could begin changing in the days ahead. Though NOAA's Storm Prediction Center has recorded only a quarter of last year's reports of twisters to date (93 reports versus last year's 394), severe weather threatens regions of the Plains states each of the coming three days. The severe weather threat could extend north into the southern Midwest Friday and Saturday.
Dear Tom,
Will ash from the Iceland volcano eventually affect the weather in Chicago?
---Michael Fisher
Dear Michael,
It isn't likely to, given the intensity of the eruption to date. Unless the blast intensity of the volcano that has erupted beneath Iceland's Eyjafjallajokull glacier should greatly increase, volcanologists believe the plume of steam, dust and ash being injected into the atmosphere will have no measurable effects on the world's climate as a whole or the climate of a specific location, such as Chicago.
The amount of ash ejected thus far is not sufficiently great. Jeff Osiensky, volcano ash program manager for the National Weather Service, says, "The likelihood of any ash even reaching into far eastern Canada is pretty unlikely at this point."
Only a week ago, Chicagoans bask in 80-degree warmth---one of four 80-degree and warmer temperatures already on the books this year. Only five of the past 140 years has seen as many 80s this early. But, weather records reveal years which have been front-loaded with 80s often slow down---at least for a time---in their warm weather production. Three of those five years managed a grand total of just one additional 80-degree day between now and May 20. The period typically hosts five 80s.
Working against the return of warmth Wednesday is the predicted arrival of a "back-door" cold front. The name comes from the fact such fronts "back" into the Chicago area from the northeast instead of approaching from the west as do most weather systems which cross the Midwest. The passage of Wednesday's back-door front is to send temperatures tumbling into the 40s near Lake Michigan Wednesday afternoon and evening.
While the day opens with gentle southwest winds which, in combination with converging winds along the incoming front produce a bit of compressional warming with possible 60s primarily in south and southwest suburbs---northeast winds are to follow this afternoon. They will strengthen once the front passes. These winds are to arrive having traveled nearly the full length of chilly Lake Michigan to get here. Falling temperatures are likely to ensue. The cool air mass which takes hold Wednesday night into Thursday will be quite shallow and computer models hint at a moist layer just above which is likely to bring more clouds and a few sprinkles into the area.
Suburban temps away from the lake flirted with 70-degrees Tuesday
While O'Hare topped out at 64-degrees Tuesday, the warmest inland locations managed 70-degree highs. Unofficial highs at Weather Bug Sensors included 74-degrees at Marseilles, 71 Geneva and New Lennox and 70 at Elgin and south suburban Steger.
Prolific rains predicted with weekend storm would be Spring 2010's heaviest
Area farmers will be working hard in coming days to complete the planting of this year's corn crop. That's because big rains--some the offspring of thunderstorms---appear to be targeting the Chicago area this weekend. There are indications from a suite of computer models that the incoming system could become the spring season's wettest storm in Chicago and over a huge swath of the Midwest. Though rains may sweep the area in waves---with any breaks in the precipitation difficult to time at this distance---total weekend rainfall could fall in the 1 to 3 inch range.
The Chicago area marks the 43rd anniversary of its worst tornado outbreak, which included the deadly Oak Lawn and Belvidere twisters
The day hadn't been exceptionally warm or exceedingly humid. Temperatures April 21, 1967 peaked at 74-degrees at Midway Airport and dew points, a measure of atmospheric moisture, were modest as well, reaching the low 60s. But the spring storm riding a 120 mph jet stream, with branches which split over the Midwest signaling that air was ascending and cooling on a massive scale, was destined to become a killer. A tornado watch was issued at 1:50 pm. by the Weather Bureau (that's what the National Weather Service was called at the time) covering the entire Chicago area and virtually all of northern Illinois and southeast Wisconsin. It ran through 8 p.m. in evening.
Twelve twisters had been reported by 3 p.m. It was at 3:50 p.m. that the day's first killer twister touched down in Belvidere just as school was letting out. It tossed 12 school buses about, hurling one across a corn field. The tornado killed 24 people---13 of them at the Belvidere school, making it the 6th most deadly tornado strike on a U.S. school. It injured 410 as is raced east into McHenry County toward Woodstock where a second twister developed.
Horrible as that storm was, an even more disastrous tornado was to dip from Chicago area skies over Palos Hills at 5:30 p.m. then race at 65 mph into Oak Lawn, Hometown, Evergreen Park and the South Side of Chicago before dissipating a mile out over the lake east of the Museum of Science and Industry. The tornado had crossed the Dan Ryan Expressway at the height of rush hour and killed motorists in their vehicles in Oak Lawn. Its deadly trek, which produced F4-level damage (with winds estimated at 207 to 260 mph), killed 33 and injured 1,000.
Key intensity index "ups" Icelandic volcano's strength; eruptions continue
While a number of aircraft returned to the skies over Europe Tuesday, ash continued spewing from the volcano beneath the Eyjafjallajökull glacier in Iceland. Its Volcanic Explosivity Index (VEI) rating has been increased to a "3" by a number of researchers. The 8-level VEI Index was developed by U.S. Geological Survey scientists as a means of categorizing the severity of volcanic eruptions, taking into account the height of their plume, the volume of ash released and duration of eruption. Though higher than the initial rating of "1", the Icelandic eruption is still short of the "5" rating for Mt. St. Helens and the "6" VEI rating for the Mt. Pinatubo and Krakatoa eruptions.
Dear Tom,
My husband and I have a bet regarding snow totals: Which winter was snowier, this one or last?
--Lori Nell
Dear Lori,
By an inch and a half, this winter's 54.2 inches topped last winter's 52.7 inch total. It appears that the 2009-10 snow season is over, though an additional 0.1 inch or so can't totally be ruled out as measurable snow has fallen in Chicago as late as May 11 (in 1966 when 0.2 inches fell). Adding the 60.3 inches that fell in 2007-08 to the mix, Chicago's last three winters mark only the second time since 1885 that the city has recorded three consecutive 50 inch-plus snow seasons. The other snowy trio was the incredibly snowy Chicago winters when 54.1 inches fell in 1976-77, 82.3 inches in 1977-78 and 89.7 inches in 1978-79, the city's all-time snowiest winter.
The chilly temperatures of recent days, despite the abundance of sunshine, have been a sobering reminder just how unusual last week's 80s were. Only five other years have paralleled this spring in producing as many (four or more) 80-degree or warmer daytime temperatures so early in the warm season---including 1976, 1977, 1986, 2002 and 2003. The number of 80s which occurred in those years in the month from April 20 to May 20 is instructive.
Early occurring 80s offers little assurance such warmth will keep coming in the short term. Only three of those five years ---1977 and 1986---managed more than the five 80-degree or warmer temperatures which is typical for the period. That puts the historic probability that 80+ degree temperature production will slow after coming on so strongly early in the season at 60 percent!
An abundance of sunshine filters filters to earth Tuesday through the day's high clouds and temps may respond by warming modestly away from the lake. But Chicago's prevailing spring winds offer compelling evidence why long streaks of warmth tend to be few and far between this time of year. Some form or easterly wind, riding off the lake's still bone-chilling water, typically occurs in Chicago 48 percent of the time in April. The season's strengthening sunlight joins forces with Lake Michigan's bone-chillingly cold water to generate on-shore winds.
Spring's easterly winds blow in several ways here. They can occur as highly localized, limited-coverage circulations which develop in the absence of a large scale weather systems which capable of producing well developed wind regimes. That's what happens Tuesday.
Or, easterly winds can be well organized and cover a good deal of real estate. That's that the sort of wind regime predicted to lock in Wednesday afternoon and evening in the wake of a southbound cold front's passage and send temperatures broadly lower.
Illinois farmer's have over a third of Illinois' corn planted
The progress which has been made planting corn across Illinois and the Midwest by the regions' farmers offers a stunning illustration of how much better this spring's weather has been than last. With rainfall running half last years', early field work has contributed to 34-percent of the state's corn crop being in the ground already.
Windy late week/weekend storm could bring area's heaviest rain here in 3 weeks---potentially spring 2010's heaviest yet!
A windy, wet storm threatens to come together later this week. It's a development which could unleash the heaviest rains on the Chicago area this spring (since March 1). The average of the rainfall generated by most recent ten runs from the National Weather Service's GFS (Global Forecast System model) puts an estimate of the metro area's 7-day rainfall at nearly twice normal. And estimates of two week rainfall surge to 2-3 or more inches--also well above normal and, if true, quite a change from the spring season to date.
Icelandic volcano behind European air travel chaos not huge compared to other well known eruptions
The air traffic debacle in Europe over the past week--- the worst to occur since World War II---has stranded millions across the region far from home. Yet, the volcano responsible ranks near the bottom of the U.S. Geological Survey's eight-level Volcanic Explosivity Index (VEI). The index quantifies the severity of eruptions by taking into account the height to which a volcano's plume rises, the volume of ash released and the period over which a volcanic eruption takes place. The index assigns the past week's eruption in Iceland a "1"---next to the lowest ranking in terms of intensity. By comparison, the index ranks the Mt. St. Helen's eruption in 1980 and El Chichon in 1982 a "5", while Mt. Pinatubo in 1991 and and Krakatoa in 1883 a "6" and Mt. Tombora in 1815 a "7."
Though eruption intensity in Iceland appeared to be easing Monday with a number of airline flights cleared to resume, the intensity of volcanic eruptions can change quickly.
Dear Tom,
How many days a year, on average, is a Chicago record for high or low temperatures broken? I'm guessing it can't be many.
--Scott Anderson Utica, Ill.
Dear Scott,
You're correct -- it isn't very many. Chicago's daily temperature extremes are derived from an official period of record from Nov. 1, 1870. Wide-ranging temperature fluctuations during that lengthy period have pushed the city's daily temperature records pretty far "out there" and those extremes are not often challenged.
On average, a new daily high or low temperature record is established or tied only six times per year. Chicago's official thermometer at O'Hare International Airport registered only one new daily temperature record in 2009 and, as of April 1st, one in 2010: 83 degrees on April 1.
By Steve Kahn, WGN-TV Weather Center Meteorologist
Despite nearly cloudless skies this weekend, the chill induced by brisk northeast winds off still-cold Lake Michigan was a reminder to Chicagoans that last week's highs in the lower 80s were the exception and not the rule this early in the spring. After a cold morning that brought frost and subfreezing temperatures to inland areas away from the city, readings hovered near 50 degrees much of Sunday. Temperatures will begin to moderate Monday after another chilly start and fluctuate through the 60s much of the week. Sunshine has been in abundance here so far this month with the city receiving 67 percent of the possible amount, making this the sunniest April to date since 1976.
Rains hit Texas, Oklahoma
A prolonged period of showers and thunderstorms has been soaking portions of Texas and Oklahoma since last Wednesday, bringing flooding to portions of the area. Heavier storm totals in Texas include 11.10 inches at Orange Grove (near Corpus Christi) and 8.68 at Medina (near San Antonio). South of Oklahoma City, Loco, Okla., measured 3.25 inches of rain.
Dear Tom,
Does a lot of April 80s mean a hot summer?
William J. Ooms Jr., Alsip
Dear William,
Not necessarily. Checking the data with the help of Chicago climatologist Frank Wachowski, no correlation between April 80s and summer 90s was found.
Based on Midway Airport data since 1928, Wachowski noted that while other Aprils had produced more 80s, 2010 is the first to record four in the first half of the month. Midway has logged seven summers with 40 or more days of 90 degrees or higher, and in those seven years the number of April 80s averaged less than two.
Conversely, the 14 other Aprils with four or more 80s produced an average of 22 90-degree-plus days -- one less than the long-term average of 23.
Notably, in the hot 1988 drought summer the city sweltered through a record 48 days of 90 degrees or higher, yet that April could only muster a single 80, that on April 5 when the high temperature reached 85.
Saturday's 59 degree high felt a bit chilly to spoiled Chicagoans after last week's 80s, but though it was the coolest reading here in more than a week, it was still one degree above normal. Clear skies and light winds Saturday night allowed temperatures to drop into the 20s and 30s across much of the metropolitan area bringing a frost or freeze to most areas away from the heart of the city and the lake. Sunday promises a repeat performance with sun-drenched highs mainly in the 50s followed by another overnight round of frost and freezing conditions .
Dry and milder until late week storm
Temperatures will slowly moderate through the 60s in the week ahead, though onshore winds will repeatedly hold readings near the lake in the 50s. Though soil moisture remains adequate here after a snowy winter, significant rainfall has eluded the Chicago area since April's opening week. Rain from Friday's cold front bypassed much of the region bringing only some light showers to southern sections. However, prospects look good for a substantial rain event later this week as a storm system develops in the Plains.
Dear Tom,
If a trace of snow fell every day of the month, what would the reported monthly snowfall be?
---Ed Kozak, Chicago
Dear Ed,
In a word, trace. Longtime Chicago weather observers Frank Wachowski and Paul Kubecka informed us that a trace of snow or rain is an amount too small to measure and is not cumulative from day to day. Hypothetically there could be a trace of precipitation every day of the year and the annual precipitation would still be a trace. They did note that on an hourly basis traces can build into measurable precipitation (0.01 inch for rain and 0.1 inch for snow) in an ongoing precipitation event. If very light rain or drizzle was falling, there could be a trace after one hour, but the total could build to 0.01 inches the next hour, resulting in measurable precipitation for the day.
By Tom Skilling
The past week's 80s--welcome, yet incredibly out of place this early in the season--have been replaced by more seasonable temperatures. Frost patches threaten to occur in colder locations Saturday and Sunday nights as wind gusts, expected to build at times to 20-25 mph Saturday, ease within the exceptionally dry air mass which has overspread the Midwest from Canada. Dry air cools quickly once the sun goes down and winds decrease, so nighttime temperatures are likely to dive precipitously as the darkness of night takes hold. With dew points--a measure of the air's moisture content and, at times, indicators of where nighttime low temperatures may be headed--in the 20s, there's compelling evidence normally colder locations away from the city and Lake Michigan's warmth are headed for the 20s in coming nights.
This is quite a change in an April which has boasted very-un-April-like weather to date! Mind you--few here are complaining. A number of area farmers are already out in their fields planting--the earliest that's happened in recent memory and a far cry from last year's abysmally wet season which kept the planting process going into June. Many who farm here consider the 2009 season the worst in memory--possibly the worst ever.
This month is also running a rare 12-degree temperature surplus to date with more 80-degree or warmer temperatures on record this spring--four of them--than in all but one other year (1986) since 1871. When the abundance of sunshine is factored in--the area's been treated to 62 percent of its possible sunshine compared to 42 percent for the full month of April a year ago--the picture which emerges is especially appealing.
The month is embedded within a meteorological spring season which has averaged 7 degrees warmer than the same period in 2009. Saturday's 56-degree predicted high will fall 26 degrees below Thursday's 82-degree peak and 18 degrees off the 74 recorded a week ago. But, it ends up close to the 59-degree normal high for the date.
Icelandic volcano's ash clouds expand into Russia; only two-thirds of Europe's estimated 28,000 flights operated Friday
The massive cloud of volcanic ash released by an Icelandic volcano during its second eruption in a month continues to play havoc with European air travel. It expanded into western Russia Friday.
By one estimate, two thirds of Europe's 28,000 daily flights had to be cancelled Friday due to concerns over the devastating effect of ash on aircraft. And, volcano experts there say it is difficult to know how long the situation may continue given the fact that forecasts of future volcano behavior are difficult--in many cases impossible.
The early read on whether Wednesday's eruption is likely to cool global temperatures, as has happened with some larger volcanoes in the past, is that the eruption in Iceland is smaller than more memorable volcanoes. The UK Met Office suggests most of the ash is situated between 20,000 and 30,000 feet--the region of the atmosphere within which clouds and precipitation take place. That's important because such ash can fall out of the atmosphere on its own or be precipitated out more easily than when blasted into the stratosphere--the layer above. Ash can reside there for longer periods of time and be disseminated globally by stratospheric winds.
Volcanoes in the past which have erupted on a massive scale and with such force that particulates and ash have been propelled into the stratosphere have tended to be the ones responsible for the most widespread global temperature reduction. To date, this eruption doesn't appear to fit that mold. But, experts are monitoring the situation carefully, mindful that future eruptions could end up sending more ash and particulates into the stratosphere--a development which could lead to cooling.
Dear Tom,
A few years ago, on an unseasonably hot April day, a sudden wind shift dropped the temperature 20 degrees in a matter of minutes. Was that a record?
--Sharon Tamura, Chicago
Dear Sharon,
Having Lake Michigan on our eastern doorstep makes Chicago a prime candidate for rapid temperature drops during the spring. With the slow-to-warm lake water temperatures hovering in the 40s, a sudden wind shift to the northeast can send lakefront temperatures crashing. We searched in vain for the event you remember, but a classic lake-induced temperature drop in 1963 likely produced similar results. On May 9, 1963, the temperature soared to 84 degrees. Then, just before 2 p.m., a fast-moving cold front sweeping south down the full-length of Lake Michigan reached Chicago and the temperature dropped to 62 degrees -- a record 22-degree drop in 90 seconds.
The string of unseasonably early 80+ degree Chicago highs Wednesday and Thursday has ended. Such warmth WILL ultimately return---but not any time soon. Longer days, more direct sunlight and warming lake waters all contribute to seasonal warming here, but the process is a slow one. Blips of warmth, like the June-level 80 and 82-degrees peak readings observed in recent days, DO happen---but not on regular basis.
The back-to-back 80s just logged Wednesday and Thursday brings to four the number of 80s which have been recorded so far in 2010 in the city. Only once before---in 1986---have four 80s been tallied this early in the season.
Coming days will see a noticeably cooler pattern take hold---one expected to continue through next week and to include the frequent development of east to northeast winds off chilly Lake Michigan waters from next Tuesday forward. A buckling jet stream tugs cooler air in from Canada which is to drive this cool down.
From 82-degrees Thursday afternoon to Sunday's potentially frosty 31-degree open (at O'Hare) temperatures will shed more than 50-degrees---the equivalent of moving from the heart of one season to the next in just a few days time.
Warmest April open in 139 of weather records here
The magnitude of the recent warmth has been impressive. Uninterrupted sunshine, low relative humidities and strong subsidence beneath a powerful pocket of jet stream winds have been critical in generating this week's early season warmth.
Thursday's high of 83-degrees at Midway and 82 at O'Hare helped boost April's average temperature to 56.8-degrees. It's a reading which makes the month's opening 2 weeks the warmest April 1-15 period here in 139 years of weather observations. The reading is an astounding 11.8-degrees above normal (45.0-degrees) and 15-degrees above the same period a year ago. This week's highs have been more typical of June than mid April.
Average date of last 32 comes later this month; frost threat historically lingers into May
Frost is a threat this weekend---both Saturday and Sunday nights. The average date of the city's final 32-degree temperature of the year occurs on or about April 26 at O'Hare and April 20 at Midway. But these dates don't mark the final dates for frost since freezing temperatures can occur at ground level even when thermometer level readings (taken about 6 ft. above the ground) are in the mid 30s. For that reason frost can remain a threat into May.
Volcanic ash playing havoc with European air traffic
Ash streaming off a volcano in Iceland led to the cancellation of 4,000 flights across Europe Thursday---a number officials fear may grow to 6,000 Friday. It's the worst interruption in international air travel since immediately after 9-11.
Ash from volcanoes has been known to extinguish jet airplane engines and produce serious damage in the past. Over 100 incidents involving volcanic ash were recorded between 1983 and 2000---including a terrifying five minute, 14,000+ ft. dive over Alaska's Talkeetna Mountains north of Anchorage by a KLM 747 with 231 passengers. An eruption of Mt. Reboubt had sent ash into the air which shut down all four engines of that aircraft, sending it into a fearsome plunge from 27,900 ft. to 13,300 ft. before pilots managed to restart the engines. The ash produced $80-million in damage to the aircraft and its engines.
Dear Tom,
I maintain Chicago usually gets snow in April, and sometimes a lot of it. Friends disagree. Rescue me!
--Pia Kruse
Dear Pia,
Consider yourself rescued. Chicago's snow season winds down in April, but wintry weather still asserts itself often enough, though briefly, and in rare instances it has delivered April snowstorms that would do January proud.
A computer scan of Chicago's snow data, 1885 through 2009, reveals that snow has been observed in 113 Aprils out of 125 (that's 9 out of 10 Aprils). Most of the Aprils with snow, 78 of them, registered only traces or a few tenths of an inch, but 35 Aprils produced at least 1 inch and four had 10 inches or more (1938, 1970, 1975 and 1982). The April snow record was in 1938; on April 6 that year, 9.0 inches fell and on April 8, 4.5 inches; temperatures held in the 20s and 30s through that period.
It's been 33 years since Chicagoans have been treated to spring temperatures as warm as this season's to date. In the wake of June-level 80s Wednesday, a second day of 80s appears a good bet Thursday. It's a development which would bring to FOUR the number of 80-degree or warmer temperatures this season. There's been only one other year (1986) since weather records began in 1928 at Midway Airport with as many 80s this early in the season.
This spring's weather has been the polar opposite of a year ago when frequent rains, wet soil and abnormally chilly temperatures played havoc with spring planting. Farmers' attempts to get out into the area's waterlogged fields proved all but impossible as the rain and chill kept coming, further soaking already saturated soils. It led to a planting season considered by many the worst ever.
Some area farmers off to the earliest planting in memory
Stung by last year's mix of wet, cold weather, no time is being wasted in getting out in the fields this year. Rainfall on a statewide basis since March 1 is off as much as 2 to 6 inches from a year ago. The effect has been dramatic. Dave Khester, who farms 1,000 acres in Will County east of Wilmington believes this may be the earliest he's ever started planting. He reports field conditions are excellent, adding that while the top soil is a bit dry, there is adequate moisture for seeds to germinate.
There could be one a drawback to early planting, though it's hardly a certainty, says John Hazzard, who also farms in Will County. That's the potential for cold, frosty weather between now and late May. In such an instance, he says, "Planting this early in the northern part of Illinois would not have turned out to be a very good idea."
Meteorological spring reaches its midpoint
Chicago's official 46.1-degree average temperature at O'Hare since March 1 is 6-degrees warmer than a year ago and 7-degrees above the 140 year average. It puts meteorological spring 2010, which began March 1 and reaches its halfway mark Thursday, among the 8 warmest early spring seasons of the past 140 years.
Wednesday's warmest area highs included 86 in the Fox Valley at Geneva, 86 Buffalo Grove, 85 Phoenix, Illinois (near south Holland), and 84-degrees at Plainfield, Downers Grove, La Grange, Wilmington, Aurora and Joliet
Blocking pattern in the arctic still impacting Chicago's weather
The current warm spell is likely to be a brief one. Markedly cooler weather arrives in stages beginning Friday. A suite of forecasts produced by National Weather Service supercomputers indicate a blocking pattern in northern Canada east to Greenland---a "signal" of cooler than normal weather overall for Chicago.
Dear Tom,
How accurate are the forecasts in "The Old Farmer's Almanac"?
--Lisa Crowne
Dear Lisa,
A few years ago "The Old Farmer's Almanac" cited an accuracy rate of 80 percent. That seems high, at least based on the admittedly limited personal experiences of the people here in the WGN weather center.
The results of a study in the middle 1980s by Dr. John Walsh of the University of Illinois seem more believable. His study focused exclusively on the almanac's monthly temperature and precipitation trend predictions -- whether the month was to be above or below normal. Walsh was quite lenient: If the outlook called for slightly above-average temperatures but the month turned out to be much above, he credited that as an accurate prediction. On that basis, the almanac scored 52 percent accuracy -- hardly exceptional, but, as Walsh put it, on the "right side" of the 50 percent accuracy of a coin flip.
It's official! We've hit 80-degrees Wednesday at both O'Hare & Midway at 3pm. Midway's up to 81-degrees at 4 pm.
There are now three official 80s on the books (at O'Hare) for 2010. We hadn't tallied three 80-degree or higher temps
until May 20th a year ago---a full 5 weeks later than today (April 14)! Only 5 of the past 81 years have had as many 80-degree or higher temperatures on record this early in the season at the city's Midway Airport observation site.
It's worth noting that of 9 years with two or more 80s on record by now, six of the 9
went on to produce more than the long-term average of 23 days with 90-degree or higher temperatures at Midway Airport site. The average 90-degree or higher tally
among these nine years was 29!
Other Weather Bug and NWS Chicago metro area temps at 4pm include 87 Marseilles, 86 Plainfield, 85 Buffalo Grove, 84 Pontiac and New Lennox and 83 at De Kalb,Peru, Itasca, Calumet City, Munster IN and 82 Minooka, Griffith, University Park, and 82 Highland and Rensselaer in Indiana.
Another unseasonably warm day is ahead Thursday--then a pattern change gets underway. That plus a look at rain prospects in coming weeks as area farmers, slowed by last year's extremely wet weather, begin moving into their field to fertilize and plant the 2010 crop.
Tom Skilling
The Chicago area's third and fourth 80-degree highs of 2010 are on the way Wednesday and Thursday afternoons, if current forecast trends continue. That's rare temperature territory for so early in the season. Computer-generated wind trajectories which enable meteorologists to track air masses indicate the warm air predicted in Chicago Wednesday has swept in from southern Missouri and Arkansas where it sent Tuesday highs into the low and mid-80s.
Not until May 20---five weeks beyond this date---had three 80s occurred here a year ago. The 81 predicted Wednesday afternoon is over 20-degrees above normal and more typical of June than mid April. It is the warmest air to reach the metro area in two weeks and makes this only the fifth of the past 81 years to have hosted three 80s so early in the season.
Lake cooling, still evident from lakeshore areas of Chicago northward as Wednesday gets underway is expected to shift into far far north lakeshore communities as the day proceeds, restricting highs to the 60s there.
This month is averaging nearly 11-degrees above normal in Chicago, the warmest up to this point in any April over the past 81 years. And 70 percent of days since meteorological spring 2010 began March 1, have been at or above normal---a development which has slashed estimated home heating to 25 percent of normal.
Tuesday's 80s reached to within 75 miles from Chicago
Easterly winds off Lake Michigan restricted Tuesday highs to 63-degrees at O'Hare even as downstate temperatures surged above 80. Illinois 80s extended north to Marseilles, only 75 miles southwest of Chicago. Pontiac reported a high of 82, while readings peaked at 84 degrees in Champaign, Springfield and St. Louis.
Early 80s have boosted Chicago's summer 90-degree prospects in the past
There have been 9 years which have produced two or more 80s by this date. The summers which have followed have gone on to produce an average of 29 days at or above 90 at Midway Airport. The site's average count the past 81 years has been 23. By comparison, only 7 occurred there a year ago while only 4 were tallied at O'Hare---the city's official observation site.
60 mph winds topple highway signs, send dust airborne in the Plains
Powerful non-thunderstorm southerly winds topping 60 mph raked sections of the Plains Tuesday toppling some highway signs along I-80 in Nebraska and sending clouds of dust into the air by the roaring winds. A late day squall line which extended from from Colorado north to the Dakotas, included cloud tops scanned to heights of 50,000 feet by Doppler radars in the region. One storm produced a tornado just southwest of Bethune in eastern Colorado near the Kansas border.
Dear Tom,
Has Chicago ever experienced an official 100 mph wind speed?
-Skip Roberts, Lemont
Dear Skip,
Excluding tornadoes, a triple-digit wind speed, sustained or gust, has never been officially recorded in Chicago. The city's official records list the highest sustained wind at 87 mph blowing out of the northeast during a ferocious snowstorm Feb. 12, 1894, that brought 10 inches of snow and widespread property damage to the city. Throughout the years, severe thunderstorms have delivered unofficial 100-mph gusts around the metropolitan area. One particularly violent storm struck in the late night hours Aug. 26, 1965, and produced gusts of 100 mph at Lemont, 90 mph at Joliet and 88 mph at Midway Airport. O'Hare International Airport's highest official gust was clocked at 84 mph during a severe thunderstorm on March 27, 1991.
Not even strong southeast winds off Lake Michigan's chilly waters could deny Cubs fans 60-degree temperatures for the team's home opener Monday. Though the air was a bit nippy out of the sun or in areas most exposed to the wind, Monday's 62-degree high in Wrigleyville was the mildest on an opening day there in 15 years. Not only was the reading well above the rain-soaked 46 with which the home season opened a year ago, Monday's warmth was accompanied by sunshine which made its way through an often thick canopy of high clouds. The day's high was 5-degrees above normal for the date---just the latest temperature surplus to occur in a Chicago April which has averaged 55.2-degrees; nearly 11-degrees above the long term average and 14-degrees ahead of April a year ago.
Warmest April open in 81 years has lake temps warmer too
Even Lake Michigan is responding to the mild spring. The 51-degree water temperature taken by the City of Chicago Water Department at the Jardine Water Purification Plant is 8-degrees above the 43-degree reading there a year ago. Water temperatures offshore at the Crib are at 47-degrees versus 41 a year ago.
Easterly winds drive the huge west to east temperature spread observed Monday across the Chicago area
One didn't have to move far from the lake Monday to enjoy even warmer readings inland. Midway topped out at 71---but southwest suburban Romeoville managed 73 and Rockford recorded 72-degrees. O'Hare's 70-degree high marked the seventh time this year the mercury made it to 70. The high brought to seven the number of 70-degree days already on the books---well ahead of the long term average of 3 by mid April.
The set-up is a bit marginal, but several showers, even a t-storm, may flare here north of stalled front
A front stalled south of Chicago---the demarcation between 80-degree air downstate and in the Plains and the lake cooled, lower water content air draped across northern Illinois and Indiana as well as Wisconsin and Michigan---may focus scattered shower and thunderstorm development in parts of the area Tuesday. Areal coverage isn't likely to be very high--perhaps 20 to 30 percent of the area. But, the spots affected by these showers may experience strong wind gusts and brief downpours.
The most supportive atmospheric conditions for thunderstorms are in place to Chicago's west in the Plains Tuesday and Wednesday. As the warm frontal boundary begins a northward drift, conditions most supportive of storm development will shift north too---only to sag southward into the metro area late Thursday or Thursday night.
Rainfall since March 1 only 2/3ds a year ago
Chicago's rainfall since March 1 is at 3.85 inches--roughly two-thirds last year's 5.89 inches to-date.
Dear Tom,
We recently visited the observation deck atop the Hancock Building. The wind up there was blowing at 48 mph but the reported wind at the ground was 8 mph. Can this be correct?
---Evan Moser
Dear Evan,
Moving air -- wind -- loses energy to friction with the ground and so wind speeds at the ground are typically much less than higher up. In the lower several thousand feet of the atmosphere, winds blow progressively stronger with increasing altitude as the effect of ground friction diminishes. Consequently, a 48-mph wind at the top of the 1,127-foot John Hancock Building with an 8-mph wind at the ground is an entirely normal situation.
On a fair night, surface wind diminishes to calm as a layer of cool, stable air develops upward from the ground several tens of feet, but a few hundred feet aloft the wind is still blowing with unabated strength.
A mild week is in store for the Chicago area with high temperatures expected to remain at or above normal. Highs in the 60s will be the rule early on, though persistent lake winds will restrict shore area readings to the 50s. By midweek a warm front will pass, setting up a gusty southwesterly wind flow that should send temperatures soaring toward the 80-degree mark.
Precipitation should not be a major factor during the week, though a few passing showers and thunderstorms are possible Monday night and again toward the end of the week when the arrival of a cold front sends temperatures tumbling back to seasonable levels.
Decent weather for Cubs home opener
Cool easterly off the lake breezes will hold temperatures in the 50s at Wrigley Field Monday, but partly sunny and dry conditions should prevail -- a far cry from the rain and chill that plagued last season's home debut. Forty-six years have elapsed since the Cubs last truly warm home opener: an 84-degree April 17, 1964, against the Philadelphia Phillies.
Dear Tom,
I remember going to a Cubs game on June 2, 2001, and freezing. What was the weather like that day?
-- Rich Lurie, Chicago
Dear Rich,
Freezing at Wrigley Field is a common occurrence during the early part of the season anytime the wind blows in off of still chilly Lake Michigan with its typical water temperature in the lower or middle 40s. The day before your game on Saturday, June 1, the weather was mostly sunny and hot with temperatures at the ball park topping out at 93 degrees. However, some thunderstorms hit Sunday morning and winds swung into the east -- and the temperature plummeted (although not to freezing levels). By first pitch readings hovered in the lower 60s, a drop of 30 degrees from Saturday. The Cubs prevailed that chilly Sunday, beating the Houston Astros 4-2, hopefully making the cold weather a bit more tolerable.
In a span 34 hours Chicago temperatures climbed from a Friday morning low of 30 to a balmy high of 74 degrees on the driven by gusty southwest winds Saturday afternoon, a testament to the large temperatures swings that typify Chicago spring weather. Temperatures will take a brief downturn Sunday and Monday as winds blow in off chilly Lake Michigan keeping temperatures in the 60s except near the lake where 50s will prevail. A burst of warmth should arrive midweek as southerly winds return pushing the mercury to around 80 degrees and overcoming any lake cooling bringing the city its warmest weather since the back-to-back highs in the 80s on April 1-2.
80 years ago Chicago's earliest 90s then a chill
On April 10-11 in 1930 Chicago was in the midst of a mini-heat wave when the city recorded two consecutive highs of 90 degrees, the earliest on record. The heat was fleeting and within two weeks the weather turned downright chilly with five straight days with highs in the 40s and 50s and lows in the 30s.
Dear Tom,
Is there a prognostication about the upcoming hurricane season?
---Jim Mudrak
Dear Jim,
The Tropical Meteorology Project at Colorado State University has just released its preliminary outlook for the 2010 hurricane season in the Atlantic Basin. Headed by Dr. William Gray, the forecast group expects an active hurricane season with a total of 15 named storms, including eight hurricanes, of which four are expected to be major (Category 3 or stronger).
The anticipation of an active hurricane season arises from two important factors: Warm water (as of the end of March, the portion of the Atlantic Ocean over which hurricanes form is warmer than it has ever been at this time of the year) and diminishing el Nino (abnormally warm water in the tropical Pacific Ocean). El Ninos generate unusually strong upper-level winds that tear apart developing hurricanes, but the current El Nino is fading.
The mercury will climb into the lower 70s Saturday -- a surge of more than 40 degrees from Friday morning's frosty lows near 30 as April regains its warm ways. Despite the recent chill, April (with an average temperature of 55.0 degrees) is running nearly 11 degrees above normal and nearly 7 degrees ahead of last year. It's the sixth warmest April open on record dating back to 1871.
A frontal system will bring clouds and some thunderstorms to the area Saturday night, setting the stage for a somewhat cooler Sunday as east winds hold inland highs in the lower 60s while lakeside areas remain in the 50s. Similar conditions are on tap for Monday with onshore winds again holding readings in the 50s near the lake and at Wrigley Field for the Cubs home opener. A return of southerly winds by midweek will boost the mercury back toward the summer-like 80-degree-level readings that graced April's first two days.
Hurricane season may be an active one
The first forecasts for the 2010 hurricane season issued by the Colorado State University research team led by Dr. William Gray are calling for an active season with 15 named storms and eight hurricanes -- including three major ones (Category 3 or higher with sustained winds of 111-plus mph).
Dear Tom,
When does Chicago usually get its first 80-degree temperature? Its first 90-degree temperature? What are the earliest and latest dates? How many days per year do we usually get?
--Brian Peleski
Dear Brian,
A computer scan of the Midway Airport temperature record (1928-2009) yields the following statistics: The average date of Chicago's first-occurring spring temperature of 80 degrees is April 22, and we can expect 80 degrees or higher to occur on 85 days per year (about one out of five days); the earliest appearance was March 3 (in 1975) and the most delayed was June 1 (1973).
Chicago's first 90-degree temperature arrives, on average, on May 30, and we can expect 90 degrees or higher on 24 days per year (one day out of 15). The earliest-occurring was April 10 (1930); most delayed, July 21 (1960).
Thursday's wintry chill, responsible for late season snows which
whitened sections of Wisconsin and Michigan, is in full retreat Friday.
Returning sunshine is a big reason why. Not only is the sun up longer
this time of year--in fact, nearly four hours MORE than in
December--April sunlight is also stronger. It arrives more directly than
the sunshine we receive in winter because the sun treks across the sky
more directly overhead each day, increasing the energy which pours down
on the Chicago area. April sunlight is three and a half times stronger
than December sun--and it continues strengthening into June.
Daytime warming occurs as the ground heats in the sun, imparting some
of that thermal energy to the air immediately above it. Interfere with
this heating process--as happened in recent days with clouds blocking
the sun at the same time winds were blowing off 40-degree lake
waters--and temperatures grow chilly. Thursday's 40-degree high at
O'Hare is a perfect example--as well as one of this spring's four
coolest maximums to date. Chicago's high of just 40 degrees Friday
marked the first time in nearly 3 weeks that the official temperature
here failed to break above 40 and was 15 degrees below normal -- a
reading more typical of mid-March than of early April.
But cold as it was here, the metro area escaped the barrage of snow
which hit sections of the Midwest to the north. Wind-driven snow
slashed visibilities in Oshkosh, Fond Du Lac and Sheboygan late
Thursday morning to under a half mile. Wisconsin--especially the
northeast quarter of the state--as well as sections of Michigan,
including the Upper Peninsula--were on the receiving end of the late
season storm's heaviest accumulations. Suring, Wis., northwest of Green
Bay, was hit with 7" of slushy, wet snow while 6" fell at De Pere, 5.8"
at Green Bay and 4.5" at Sault Ste. Marine and Marquette, Mich.
Milwaukee and Madison reported snowfalls of 0.9" and 0.3" respectively.
Warming to kick in on all cylinders by Saturday
Not only will southwest winds strengthen at the surface
Saturday--gusting above 30 mph at times by afternoon--but upper-level
winds will have shifted from north to west, delivering Pacific rather
than Canadian air. These are developments which are to encourage higher
temperatures. But the warming process may be further enhanced as the
nose of a band of powerful jet stream winds sweeps into Chicago's
airspace Saturday. It's beneath such a feature that air sinks, warms
and compresses on a large scale. This is predicted to maximize warming
Saturday. Readings should peak in the low 70s--levels more than
40-degrees warmer than those with which Friday opens.
Gusty thunderstorms may hit Saturday night
Moisture increases slowly as temperatures warm Saturday. It's into
this warmer, moist environment a cold front moves Saturday night.
Converging winds along the front should act to lift and cool the air,
possibly resulting in thunderstorms. And any ascending thunderstorm
clouds will tower into powerful westerly winds aloft, which threaten to
whisk them along at comparatively high speed. This raises the potential
for powerful wind gusts with these storms Saturday night.
Lighter winds behind the front Sunday should allow localized easterly
lake breezes to develop which are likely cool shoreline locations.
The Cubs Home Opener to deal with easterly winds which delay the onset of warmth
Computer projections continue to indicate easterly winds off the lake
for the Cubs Home Opener Monday. Barring a change, this development
suggests that the strong warming, which once appeared likely for Monday
is being delayed until Tuesday and Wednesday. With lake waters still
cold, it's likely Wrigley Field temperatures may hold to the mid to
upper 50s while inland locations reach the 60s Monday. Highs in the 70s
to near 80 take hold Tuesday, Wednesday and Thursday.
Only 3 years since 1928 with as many 80s this early
Additional 80s by mid next week would keep Spring 2010's above-normal
temperature trend going. With two 80s already on the books, this
becomes only the third year with THAT many 80s to its credit this early.
Dear Tom,
What causes large hail?
--Thelma Dora, Chicago
Dear Thelma,
Large hail, an awesome demonstration of a thunderstorm's power, is massively destructive. In the United States alone, hail damage to roofs, automobiles and farm crops is $1 billion to $3 billion annually.
Hail forms in a thunderstorm's surging updrafts -- the columns of warm rising air that provide the storm's energy. Because rising air cools 3 to 5 degrees for every 1,000 feet of ascent, subfreezing conditions exist within the mid and upper portions of a thunderstorm, even on the hottest days.
Severe weather researcher Brian Smith says, "Hail starts as small ice particles supported aloft in the updraft, growing larger layer by layer by collecting droplets of water that adhere to them and freeze. Like the motion of an elevator, hailstones repeatedly ascend in updrafts, descend in downdrafts, eventually growing so large that they fall out of the storm."
At least some of the snowflakes hovering in Thursday's unseasonably chilly overcast may survive their descent from the 20-degree clouds in which they form despite above-freezing ground temperatures. Not all of Thursday's precipitation is likely to fall in crystalline form. Some of the flakes will melt or be mixed with cold rain. But studies have suggested snow flurries can travel through as much as a thousand feet of above-freezing air before completely melting.
With computer models predicting subfreezing temperatures dropping to within 600 to 1,000 feet of the ground at least part of the day, the prospect that at least some Chicago area residents could see the first flurries in over two weeks is real--but with no significant accumulation expected. Meteorological spring (which began March 1) is running 5 degrees ahead than a year ago, and April's opening 7 days has averaged 16.2 degrees above normal. That's warmed soil temperatures as well. This is expected to promote the melting of any snow which falls.
Snow this late in the season isn't unusual. An in-house analysis of Chicago's snow records back to 1884 indicates 108 of the past 125 seasons--approximately 8 in 10 of them--have recorded at least a trace of snow from this date forward. Late-season's snows have accumulated to 0.1" or more only a third of the time.
Average final frost dates still weeks away
The Chicago area has enjoyed five days with temperatures at or above 70 degrees this year--two of them 80 degrees or warmer. In effect, area residents have enjoyed twice the typical number of warm days to date. But, mild as it's been, the threat of frost isn't behind us yet. Tonight's chill, which threatens frost formation over at least portions of the Chicago area, is likely to drive the point home. Frosts can and do occur here well into May--even into early June in rare years. This has historically been the case despite the presence of the so-called "urban heat island" effect, which involves the shallow dome of mild air which hovers over Chicago and other major population centers. The "urban heat island" acts to hold temperatures up at night while limiting the degree of warming during the day. It's a major reason large cities are warmer at night than their rural surroundings. In Chicago, Lake Michigan plays a big role in modulating the temperatures as well. Its above-freezing waters reduce nighttime cooling as well.
The AVERAGE dates of the Chicago area's final frosts are as follows:
* April 16 at the lakefront
* April 20 at Midway Airport
* April 26 at O'Hare Airport
South suburbs hit by 1-3" thundery downpours; funnel cloud spotted Wednesday 100 miles south of Chicago
Drenching downpours were accompanied by rapid-fire lightning as they walloped Chicago's south suburbs Wednesday. Early estimates of rainfall from Weather Bug rain gauges included 2.00" Flossmoor, 1.87" Hebron, Ind., 1.34" Griffith, 1.27" Valparaiso and 1.13" at south suburban Frankfort. Doppler radar scans of the clouds responsible indicated the heavier storms towered more than eight miles into the atmosphere.
Nearly 100 miles southwest of Chicago, a funnel cloud danced across the skies over Livingston County near Chadsworth. It never touched down nor was damage reported.
Temps for Cubs Home Opener linked to wind direction and how much lake cooling occurs
Warm air is headed for the Chicago area next week. By Tuesday and Wednesday, it's possible readings could return to the 80s -- levels just a handful of degrees away from each day's records. More problematic, however, are temperatures for the Cubs home opener. Computer projections, which in preceding days had suggested southerly winds strong enough to overpower lake cooling, backed away from that solution in their Wednesday runs, hinting instead that east-to-southeast winds were likely to sweep into Chicago Monday off Lake Michigan. That's a development which, if true, would seriously limit warming Monday. It was a theme echoed by the European Center's global model (the ECMWF) as well as others.
But that line of reasoning -- the notion that cool winds off Lake Michigan will greatly limit warming Monday -- is at odds with a number of recent forecasts. This suggests that Monday's outlook is not yet set in stone. It makes the prediction one which we'll be following closely in coming days.
A warm solution for Monday is hardly dead: Of the 15 most recent computer model forecasts, 10 suggest strong south winds will be able to overcome lake cooling while 4 others suggest mild conditions overall with modest cooling thanks to southeast winds which could cool areas closest to the lake to the low 60s. Our forecast is an average of all current solutions -- putting temps in a range from the low 60s along Lake Michigan to the low 70s inland. Under this approach, a northbound warm front would bring the heart of the warmth into the area beginning Tuesday without depriving Chicagoans of a mild Cubs home opener. Stay tuned!
Dear Tom,
Did we just experience our wettest Easter?
--Dr. Lawrence Belun, Geneva
Dear Dr. Belun,
Not by a long shot. Though a burst of late afternoon and evening thunderstorms brought an official 0.80 inches of rain to the city, there have been seven wetter Easters in Chicago. The wettest one occurred in 1929 when 3.12 inches of rain soaked the city, forcing the cancellation of the Easter parade and flooding underpasses and viaducts and Chicago's fledgling Municipal Airport, now Midway. Other Easters with heavy rainfall include 1882 with 1.49 inches and 1984 with 1.43 inches, and in 2006, the city recorded a 0.88-inch rainfall.
There have also been two white Easters here, one in 1920 when 6.4 inches of snow fell and the other in 1964 when a 7.1-inch snowfall put a major crimp in holiday plans.
The stage is set not only for potentially impressive rainfall Wednesday and Wednesday night--some of it thundery---but for flakes of wet snow by Thursday morning. It's a stunning change from the area's brief flirtation with summer-like warmth Tuesday. That warm-up featured single-hour 27-degree temperature increases in parts of the metro area Tuesday. Calumet Harbor's air temperature was a case in point. There, readings jumped from 49 to 76-degrees between 2 and 3:30 p.m. Tuesday driven by the passage of a northbound warm front. At the city's official O'Hare observation site and in the near north suburbs, other impressive temperature increases occurred.
Readings at Midway Airport surged Tuesday from a morning low of 48-degrees to 78-degrees by mid and late afternoon. Only far northern suburbs remained beyond the reach of warm air. Waukegan's temperature did manage a 63-degree high-- but its neighbor to the north Kenosha, languished in the 40s and 50s. And even farther north, dense fog shrouded the Milwaukee area as chilly east winds saturated the air with moisture while slashing visibilities to a half mile.
But the city's brief rendezvous with summer-level warmth departed as quickly as it arrived. Winds at O'Hare shifted northeasterly between 7 and 8 p.m. precipitating a one-hour 14-degree drop from 72 to 58-degrees. And Wednesday may struggle to make it out of the 40s in lakeside locations.
Chicago has logged more early 70s than any year since 1986
Wednesday's 76-degree high became the 5th this year to reach or exceed 70-degrees---the largest number of 70s to occur here this early in a season in the 24 years since 1986.
A classic big rain set-up
The meteorological set-up coming together Wednesday and Wednesday night appears to be a classic heavy rain situation and must be monitored. The chill and increasingly gusty northeast winds in place as Wednesday gets underway reside in the lowest 3,000 feet of the atmosphere. Warmer, moister air is in place aloft and southerly winds there are to keep a supply of Gulf of Mexico moisture coming and thunderstorms erupting periodically. Thunderstorms which flare above shallow, chilly layers of air are referred to by meteorologists as "elevated convection" and behave like their warm weather counterparts in producing downpours.
A disturbance riding a powerful jet stream northeastward out of Kansas later Wednesday and Wednesday night is to increase the inflow of warm, moist air just above the surface while cooling air at the highest levels of the atmosphere. That's an explosive situation which is likely to increase rain coverage and intensity producing potentially heavy bursts of rain. With soils wet from recent rains, precipitation tallies in excess of 2 inches threaten to saturate soils, producing increased run-off and possible flooding.
Tuesday warmth produces dozens of records across 17 states
Extraordinary early season warmth over sections of 17 states produced new record highs in at least 50 cities Tuesday. Included were the 93-degree readings at Richmond, Virginia and at Washington D.C.'s Dulles Airport.
Dear Tom,
On the evening of July 24, 2009, I was in Apple River Canyon in northwest Illinois and we had a tremendous hail storm. The entire tri-state area was hit by severe storms. Do you have details?
---Terri Grommes, Batavia
Dear Terri,
Severe thunderstorms lashed northwest Illinois, eastern Iowa and southwest Wisconsin for almost four hours that evening. Winds were as high as 90 mph and much of the hail was between golf-ball and tennis-ball size. The hail devastated area crops, stripped leaves off trees, broke windows, dented autos and damaged roofs and siding. Power in the area was out for hours. The largest hailstone ---2.5 inches in diameter---was reported at Stockton, Ill. Heavy rain produced flash flooding in the Sterling area causing some roads to be closed.
Thunderstorms erupting along a northbound warm front turned violent over sections of northern Monday evening. Damage was so extensive in Oregon, the Ogle County community was described as "looking like a war zone" in a storm report filed just after 9 p.m. with the National Weather Service. Semis were blown over near Rochelle close to the intersection of I-88 and I-39 while gusts at Maple Park in Kane County hit 70 mph. Wind gusts hit 68 mph at O'Hare at 10:47 pm and reached 60 mph a bit earlier at Franklin Grove, between Rochelle and Dixon. Gusts of 50 mph swept DeKalb.
Truly rare 2.75-inch diameter (baseball ball size) hail lambasted Des Plaines just before 11 p.m. Breaking windows---while other thunderstorms peppered Batavia, Mt. Morris, Forreston and Morton Grove with hail---ranging from marble size to 1-inch or more in diameter. Hailstones 1.5-inches in diameter (ping-pong size) pounded Streamwood around 10:30 p.m. and Skokie at 10:55 p.m. while 1-inch hail (quarter-size) was reported in South Elgin.
Doppler radar scans indicated the storms responsible towered 50,000 ft. into the atmosphere----tall enough to tap the powerful jet stream winds and divert wind energy to the ground. The fast high speed winds also push storms along at a good clip which
Lightning was prolific. Up to 1,100 cloud to ground lightning strokes occurred in a single ten minute period at one point Monday evening.
Ferocious storms produced serious damage in sections of northwest Illinois as well. Large trees 3 feet in diameter were uprooted and toppled, taking down power lines as they fell in Milledgeville, south of Galena in Carroll County. The winds there also damaged out buildings. The downpours accompanying the storms prompted flash flood watches were issued from Freeport west into Iowa.
Thunderstorms earlier in the day produced the brief touchdown of a small tornado downstate 2 miles southwest of Hillsboro, Illinois south of Springfield. No damage was reported.
A warm front and the northward flood of the season's most humid air behind storm re-eruption-and it's not over
Warm, humid winds, responsible for 80+-degree warmth across the southern Midwest Monday, ran head-long into cooler easterly winds across northern Illinois and southern Wisconsin setting the stage for the evening storm outbreak. When winds converge at ground level, the resulting pile-up of air encourages air to rise and cool in the atmosphere. A faster than usual decline in temperature with height further encouraged the process, resulting in the formation of towering thunderheads---referred to as cumulonimbus clouds by meteorologists.
An additional cluster of storms may traverse the area Tuesday morning, becoming less numerous and more sporadic as summerlike warmth reaches into all but far northern sections of the metro area by afternoon. There southeast winds off chilly Lake Michigan may limit warming in areas from Waukegan and Kenosha and north---and still more storms may flare later Tuesday night into Wednesday morning.
Warmest April open on record
April has averaged 62.2-degrees to date--the warmest April 1-5 period in 140 years of official weather records. It's a reading 19-degrees above normal and 22-degree warmer than the comparable period a year ago.
Dear Tom,
During a summer in the early 1950s, I recall Aurora trucks picking up dead fish from the banks of the Fox River. Was hot, dry weather the cause?
--Mel Dormer, Aurora
Dear Mel,
According to records from the Aurora Sanitary District sewage treatment plants, a combination of low water flow in the Fox River and high temperatures resulted in a serious fish kill in the summer of 1953. The water temperature rose to high as 108 degrees, literally cooking the fish. In Chicago, that summer featured 42 days of 90 degrees or higher temperatures, including four days where the mercury topped 100, while rainfall was nearly two inches below normal. The following summer was also hot with 36 days of 90 degrees or higher, but rainfall was substantially higher, averaging about three inches above normal. Any low-water problems disappeared in October 1954 when a record 12.06 inches of rain soaked the Chicago area.
Temperatures soared into the middle 70s, falling just three degrees shy of the day's record high of 79 on a warm and very windy Easter Sunday in Chicagoland. Not only was Sunday's 76-degree high here warmer than the 69 recorded last July 4, but the day featured more impressive meteorological fireworks. Roaring south winds gusted to around 50 mph, setting the stage for an impressive round of late afternoon thunderstorms that brought heavy downpours and hail to the region. Most of the hail targeted the south suburbs where penny-size hail pelted areas near Tinley Park and Worth, and half-inch stones fell in Homer Glen.
Storms may precede cooling
More showers and thunderstorms are expected to erupt across the area Monday night and Tuesday as a major storm system traverses the Midwest. Some of the storms could be severe as the previously quiet 2010 severe weather season quickly revs into high gear. Cold air will sweep into the area on strong north winds in the wake of the storm Thursday, sending the mercury plunging about 40 degrees from Tuesday's expected highs near 80.
Dear Tom,
You just told us that we just experienced our earliest back-to-back 80s on March 31-April 1. But what about late March of 1986, when we reached a ridiculous 88-degree high on March 29?
-- Brian Beecher
Dear Brian,
The mercury did soar to an unseasonably warm 88 on March 29, 1986, but officially the highs recorded at O'Hare Airport both the day before and the day after came in just shy of the 80-degree mark at 79. Actually some portions of the metropolitan area did log three straight 80s during that early season warm spell including Midway Airport with mid-summer-level highs of 86, 83 and 85 on March 29-31.
The 88-degree maximum still stands as Chicago's all-time highest March and early season temperature unsurpassed until April 9-10 when back-to-back highs of 90 occurred in 1930.
Thursday and Friday's back-to-back highs in the 80s were relegated to memories Saturday as clouds and showers kept Chicago's temperatures in the 50s much of the day -- but skies cleared in the afternoon, paving the way for the city's mildest Easter in a dozen years. With increasing south-southwest winds through the day, readings are expected to rebound into the lower 70s, Sunday bringing the warmest Easter readings here since it reached 73 degrees on March 26, 1998.
The weather should be dry Sunday but a surge moisture arriving Sunday night could trigger a round of showers and thunderstorms with some hefty rainfall totals that could approach one inch in some areas. More rain is expected to arrive Monday night as a warm front moves through the city, setting the stage for what could be the season's first severe weather outbreak late on a warm, gusty Tuesday as a cold front slams through the area.
Record heat in the Northeast
A slew of high temperature records fell on Saturday in at least 30 cities across portions of eight states from Michigan to Maine. Some of the warmest readings were in New York including 87 degrees at both Watertown and Syracuse, 85 at Massena and 84 at Buffalo.
Dear Tom,
I remember a mild Christmas when guests arrived wearing light jackets that was followed by a very snowy Easter when they sported heavy coats and boots. When did this occur?
--Gene Trucano
Dear Gene,
You are recalling Christmas 1963 and Easter 1964 in Chicago. Christmas Day was sunny and mild with an official high of 39 degrees, but many suburban areas peaked in the lower 40s. In stark contrast the Easter that followed on March 29 was wintry and stands as the city's snowiest on record. The city received 7.1 inches of wind-driven snow that began just before sunrise and continued through late afternoon. Strong winds created near-blizzard conditions, piled the snow into huge drifts and produced subzero wind chills.
The realization that Chicago's temperatures have backtracked
overnight--and done so noticeably--is likely to become apparent with a
quick step out the door Saturday. Rather than Friday morning's low 60s,
Saturday dawns with 50s. A cold front has passed and Saturday morning's
rains are falling through a much cooler atmosphere than the one in
place here Thursday and Friday. But the news is hardly all bad.
Morning rains--possibly interrupted with a few isolated flashes of
lightning--are to wind down Saturday, allowing clouds to break in the
afternoon and evening. South winds return overnight and turn gusty
Sunday--a development likely to coax unseasonably mild air back into the
area by Easter Sunday afternoon. Temperatures return to 70 degrees at
that time--a reading which is likely to repeat Monday in all but
shoreline areas, where lake breezes are to take shape. It appears a
good bet THIS Easter Sunday is on track to end up the Chicago area's
mildest in 12 years. Last Easter's highs hovered in the low 50s.
Stormier weather ahead next week
A lull in the large-scale wind pattern Monday appears likely to set the
stage for lake breeze development. It's a set-up which could reach U.S.
Cellular Field for the White Sox' home opener Monday afternoon and
evening--but in modest form. Lake breezes tend to be very limited in
scale and areal coverage, so they aren't the perfect vehicle for
transporting lake-cooled air long distances inland.
Better organized large-scale winds associated with the area's next
spring storm are to follow Monday night and Tuesday. They set the stage
for another vigorous warm-up Tuesday, and the arrival of the area's
most humid air mass to date. Clusters of thunderstorms will be fueled
by this moisture, and with a strong jet stream expected to knife into
Chicago's airspace, it's possible that the season's first severe
thunderstorms could erupt.
Dear Tom,
I remember going outside without wearing a coat the Saturday before Easter when I was child in the middle 1960s. What year was that?
--Diane Marie Kloba
Dear Diane,
You are recalling Easter weekend of 1967. Easter was early that year, falling on March 26, and the warm weather was quite welcome as the city was still recovering from the 23-inch "Big Snow" just two months earlier on Jan. 26-27. The mountainous snowpack finally melted away by March 15, but a snowstorm put down a fresh 4-inch snow cover on March 20. However, temperatures surged, rising to 51 degrees on Good Friday and, just as you remember, to a delightful 75 degrees on Saturday. Easter was still mild with the high reaching 66 degrees, though some showers did dampen the day. The warm weather continued after Easter with back-to-back 70s to close out March.
It was as if the clock had been turned ahead by two months Thursday. The day's temperatures surged to early June levels and Chicagoans took to the outdoors in droves. Friday could be just as warm. The predicted high of 82-degrees, a reading nearly 30-degrees above normal, would not only tie the 1963 record for the date, it would mark the first time since official weather observations began in Chicago 140 years ago that back-to-back 80-degree highs have occurred this early in the year.
Until Thursday, the city's meteorological landscape had been void of 80-degree temperatures. At no time since the city's final 80 temperature of 2009 on Sept. 15, have readings pushed as high as Thursday's record breaking 83-degrees. The mercury first reached 80 at 12:48 p.m. and had tied the record of 82 by 1:52 p.m. Only minutes later---at 1:57 pm---O'Hare's temperature proceeded to 83-degrees. It was the first 80+ reading of 2010, retiring the 64 year old previous record of 82-degrees set in 1946. The city's other observation sites also logged 80s---including 82-degrees at Midway and 81 at the lakefront.
Chicago joined a long list of 51 cities spread across 12 states Thursday in setting a new high temperature record. Other Midwest record-breakers included 85-degrees at the Quad Cities and Burlington Iowa, 82-degrees at Indianapolis, Milwaukee and La Crosse Wisconsin, Rochester Minnesota and Traverse City, Michigan.
Winds Thursday howled gusting to 48 mph atop the downtown LaSalle Bank Building, 42 mph in Aurora and 40 mph at Lombard and Glenview.
It was warmer here Thursday then in some of the country's perennial warm spots
It's not often Chicago's weather ends up warmer than a flock of Sun Belt cities, but Thursday was such a day! The city's official 83-degree high was warmer than New Orleans (76-degrees), Phoenix (68-degrees), Las Vegas (63-degrees), Los Angeles (59-degrees) and San Diego (59-degrees).
Severe weather outbreak threatens Plains/western Midwest; rain due here Saturday
Severe thunderstorms threaten portions of the Plains, from Texas north to Oklahoma, Kansas and Missouri Friday. The storm cluster is to proceed toward Chicago late Friday night and Saturday---but in a weakening state. To date, the 2010 season has lagged recent years in severe weather production. Only 78 reports of tornadoes have been logged to date this year by NOAA's Storm Prediction Center compared to 157 a year ago and 360 in 2008.
A new storm next week is predicted to send warm air back into the Chicago area long with the year's first 60-degree dew points. The setup will have to be monitored for possible severe weather at some point Tuesday or Wednesday---and possibly as far north as Chicago.
Dear Tom,
I heard that during World War II there was a period of double daylight saving time. Is that true?
---Thanks, Alfred and Marge Engel
Dear Alfred and Marge,
There was indeed double daylight saving time during World War II, but in Britain, not in the U.S. Britain normally observes a period of summer time where clocks are advanced one hour. During the war, summer time was observed year-round but clocks were still turned ahead one hour when they normally would have been, putting British time two hours ahead of standard time. The war also prompted time changes in this country, with the U.S. going to year-round daylight saving time. The concept of daylight saving time was first proposed by Benjamin Franklin in 1784 and later advanced by Englishman William Willett in a 1907 pamphlet "The Waste of Daylight" as an effort to conserve fuel.
It's official! It may be April Fools Day--but this is definitely not a joke. We've established a new record high for the date in addition to welcoming the first official 80+ degree temperature since September 15.
The mercury first reached 80 at 12:49 p.m. and proceeded to 83-degrees just over an hour later at 1:53 p.m. breaking the previous record of 82-degrees set in 1946.
Other Chicago readings at 2 pm include Midway Airport's 82-degrees and the 78-degrees at the lakefront. The city's official high is likely to end up at 84-degrees--a reading 31-degrees above normal and more typical of June than early April.
Other 2 PM Chicago area temps off our Weather Bug network include 83 Buffalo Grove, 82 Itasca & New Lennox; 81 Fox Lake,Lansing & Downers Grove; and 80 at Kenosha, Winnetka & Elmhurst.
This level of warmth is VERY unusual at this time of the year. An in-house analysis indicates this is only the 12th year of past 140 to produce an 80 this early. The normal high is 53-degrees.
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