This Labor Day, Chicagoans should experience another nearly cloudless, warm,
low-humidity day with afternoon highs around 90 degrees. That's a reading 12 degrees
above normal for this date.
In the Great Lakes and Midwest, weather systems not only slow down but are starved of
potential moisture when hurricanes such as Gustav move out of the Gulf of Mexico and
strike the U.S. mainland.
Dry high pressure will continue to dominate northeast Illinois until Gustav moves
inland and allows some moisture to enter this area ahead of a cooling cold front
Wednesday. Temperatures the remainder of the week will be influenced by a
predominantly northeast flow that will keep highs in the 70s.
HANNA: U.S. LANDFALL STILL UNCERTAIN
With peak sustained winds of 50 m.p.h., Tropical Storm Hanna is approaching the
southern and central Bahamas.
It's still very early to determine the eventual movement of this storm as it approaches
the United States: Its potential landfall point ranges from the Florida panhandle to the
North Carolina coast.
Hanna is currently forecast to move northwest, paralleling the east coast of Florida and
intensifying to minimal hurricane strength by Thursday.
--By Paul Dailey, WGN Weather Center Meteorologist
EXPLAINER: August 2008 Archives
As August draws to a close, late-season warmth is taking up residence in the Chicago
area and should stick around at least through midweek. With the Central U.S. weather
system slowed to a crawl as two powerhouse tropical systems, Gustav and Hanna,
approach the U.S. mainland, persistent high pressure will bring warm and increasingly
hazy and humid weather to the city. Readings should climb to the middle and upper 80s
through midweek. If the mercury reaches 89 degrees Monday, it would mark the city's
warmest Labor Day since 1983, when the high reached a sizzling 95 degrees.
KILLER GUSTAV BATTERS CUBA, GULF COAST NEXT
Packing sustained winds of 150 m.p.h., Hurricane Gustav, already responsible for more
than 80 deaths in the Caribbean, slammed western Cuba, including the capital city of
Havana, Saturday afternoon. As the storm prepared to enter the Gulf of Mexico,
hurricane watches were posted from just east of Houston to the Alabama-Florida
border in anticipation of a Labor Day landfall. Wind gusts to nearly 60 m.p.h. were
recorded in the Florida Keys Saturday afternoon as Gustav's outer bands swept through
the area.
--Steve Kahn, Meteorologist, WGN-TV/Chicago Tribune
With just two days remaining in the month, August 2008 has hosted 77 percent of its
possible sunshine -- the second consecutive month this summer to do so. It's a
sunshine tally well above the 66 percent average and far ahead of last year's 57 percent.
It becomes the sunniest August to occur here in 22 years, and this weekend's sunny
weather is likely to make it the sunniest in 25 years by the time the books close at
midnight Sunday.
Chicago's official rainfall has been a fraction of last August's: 3.73 inches vs. 9.70
inches. Rain has fallen less than a third as frequently (five days vs. 16) in August
compared to a year ago. It's a far cry from the rainy manner the three-month June, July
and August meteorological summer period began. Rain isn't predicted here until the
middle of the week at the earliest.
GUSTAV MOVING OVER DEEP, WARM WATERS AND EXPECTED TO INTENSIFY
Nervous Gulf Coast residents are watching Hurricane Gustav, currently packing 80
m.p.h. top winds as it approaches the warm, deep waters between Cuba and the
Yucatan Peninsula where it is expected to become a major hurricane with winds in
excess of 110 m.p.h.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Spectacular Labor Day weekend weather awaits Chicagoans. The 50,000-foot tall
thunderstorms, which treated Downstate Illinois residents to spectacular lightning
displays while bypassing much of the Chicago area late Thursday, deposited
downpours of 3 to 4 inches and have moved on. Rain-free weather is predicted well
into Tuesday. The air mass responsible is to stall in coming days as air, vented out the
top of intensifying Hurricane Gustav -- expected to traverse the Gulf of Mexico this
weekend -- migrates away from the storm then sinks, warms and dries over much of
the eastern U.S. It's a process likely to strengthen and slow the warm air dome allowing
to it slowly stagnate here. The light, disorganized surface winds within will facilitate a
slow build-up of haze, which should become a little more evident each of the coming
three days.
The Labor Day holiday, accepted by many as an unofficial close of the summer season,
is no stranger to warm, dry weather in Chicago. Of the past 114 Labor Days, 64 have
been rain-free.
SHORTER DAYS, LESS INTENSE SUN MAKE LATE SEASON 'HEAT' MORE TOLERABLE
Readings flirt with 90 degrees inland Sunday and Monday. But humidities are to remain
low until the middle of next week.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
It was 18 years ago when 90-degree heat in combination with stifling humidities --
including tropical rain-forest level 80-degree dew points -- tangled with a cold front
and abnormally strong upper level winds to produce one of the Chicago area's deadliest
tornadoes in southwest suburban Plainfield. The storm, which hit around 3:50 p.m.,
claimed 29 lives and injured hundreds.
The weather is far more tranquil as Thursday dawns. However, thunderstorms threaten
as humid air surges back into area for the first time in five days this afternoon and into
early night. Rainfall produced by these storms will be welcome -- much of the area has
had little rain for nearly three weeks.
Wednesday's 83-degree high marked the 66th reading at or above 80 degrees this year.
Weather records indicate the area's final 80-degree day is still more than month away.
GUSTAV HAS GULF COAST ON EDGE
Residents of the Gulf Coast are understandably nervous as Tropical Storm Gustav --
weakened by its interaction with Haiti on Wednesday -- churns toward the Gulf, where
it threatens to become a major hurricane.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
This year's dry August weather is a stunning change from a year ago. Just 0.15 of an
inch has fallen at O'Hare in the 22 days since Aug. 5. That's just 5 percent of the
long-term average, and the driest Aug. 5-27 since the 0.14 of an inch fell in that period
in 1963. It's little wonder lawns are looking brown and area farmers are contemplating
spraying fields to counter a build-up of insects attracted to the dry weather. The
Chicago area had been doused by 9.67 inches in the same period a year ago -- 64
times as much rain! What a difference a year makes!
The dry weather increases the importance of any thunderstorms which erupt Thursday
or Thursday night. But those storms won't affect all areas -- just 30 to 50 percent of
the area may see a storm.
GUSTAV LURCHES TOWARD GULF
Hurricane Gustav threatens to travel over the Gulf of Mexico's infamous Loop Current
once clearing the Caribbean in coming days. That's an ominous development. Warm
water runs more than 2,000 feet deep in that region. It has fueled explosive
intensification in storms like Katrina in the past and threatens to turn Gustav into a
powerhouse storm with potential 100+ m.p.h. winds -- the season's strongest yet.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
The Farmer's Almanac -- always a fun read but an anathema to long-range forecasters
in the meteorological and climate communities -- is out with a forecast of a cold,
snowy winter ahead. It's a prediction at odds with the outlook for Winter 2008-09
produced by NOAA forecasters who project above normal temperatures and near
normal precipitation. We've been doing our own research on winters that have followed
summers with few 90s and looked at winters between El NiÒos and La NiÒas -- 27 of
them since 1950 -- because computer projections of equatorial Pacific conditions
predict that's what's ahead. Among our findings: These winters can be volatile, some
featuring large temperature swings as arctic and Pacific air duel it out. While the
number of warmer and colder than normal winters were nearly equal in these years,
there was a discernible trend for the cold winters to be significantly colder than normal.
By contrast, mild winters tended to by only modestly milder than normal. The
temperatures of all 27 winters averaged more than 1-degree below normal. The split
between snowy and not-so-snowy winters was nearly even. While full-season snowfall
averaged out near the Chicago average of 38.6 inches, winters with big snows had
some really big snows: among them 89.7 inches (1978-79).
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
With just a week left in meteorological summer, Chicago along with much of the
Midwest is locked in a comfortable autumnal-like air mass.
Record lows toppled Sunday morning when the mercury dipped to 39 degrees at Grand
Forks, N.D., and 50 degrees at Marshalltown, Iowa. Frost and freeze conditions are
expected Monday morning in portions of the Upper Midwest.
In Chicago, Sunday's high at Midway Airport reached only 78 degrees, a drop of 12
degrees after Saturday's rare 90 -- only the eighth of the year. Officially the city has
logged only three 90s at O'Hare Airport with none since mid-July. Rockford has failed
to record a single 90 so far in 2008, something that has never happened there since
records began in 1893.
Temperatures here will creep back into the 80s later this week as warmer and more
humid conditions stage a brief return.
TWISTERS SIGHTED SOUTHEAST
OF DENVER AND IN ALABAMA
Severe thunderstorms erupted along the foothills of the Rockies southeast of Denver
Sunday evening. A large, long-lived twister was sighted near Parker.
In central Alabama, Fay's remnants spawned two twisters: one near Emerald Mountain
and the other near Welona.
--By Steve Kahn, WGN Weather Center Meteorologist
Canadian high pressure centered over the northern Great Lakes will be responsible for
nearly clear skies, lowering humidities and cooler temperatures over Wisconsin, much of
Illinois and Indiana early this week. As the center of the high pressure system tracks east,
clouds will slowly increase over Chicago midweek ahead of an approaching cold front that
should bring much higher humidities and a period of showers and t-storms Thursday.
MISSISSIPPI TO BE NEXT HOME FOR FAY
As winds weaken over land, Fay will lose its tropical storm title later today, but the low
pressure system will continue to dump copious rains over the southeastern U.S. as its
center drifts almost aimlessly over Mississippi until finally being absorbed into the
late-week cold front. Incredibly heavy rains from 15 to well more than 20 inches were
reported over the Florida Panhandle Saturday, and anywhere from 10-to-20 inch totals are
expected along, and a couple hundred miles on either side of, its meandering path by
week’s end.
This second-to-last weekend of meteorological summer promises Chicagoans warm
and muggy weather with many rain-free hours. But the atmosphere is saturated with
moisture -- nearly 2 inches of it. With converging winds predicted this afternoon in
advance of an approaching cold front -- a set-up which generates a build-up of
moisture known as dew point pooling -- thunderstorm development is likely.
The manner in which Friday's thundery rains hit the area -- fast and, in terms of areal
coverage, selectively -- is instructive. Portions of the Chicago metro area may see
gusty downpours Saturday while other areas end up largely rain-free.
DESPITE LACK OF 90S, SUMMER RANKS AMONG WARMEST 33% HERE SINCE 1871
With only nine days left in meterological summer, Chicago's 72.5-degree average
temperature since June 1 ranks 46th warmest since 1871; that's among the warmest 33
percent of all years on record.
The relatively warm summer has occurred despite the lack of 90-degree-plus
temperatures. To date, only three 90s have occurred at the official observation site at
O'Hare Inernational Airport. A typical year sees 17 such days there.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
It hasn't been this muggy in Chicago in 17 days. Friday's southerly winds deliver air
dripping with nearly 2 inches of evaporated moisture with origins over the mid- and
upper-80 degree waters of the Gulf of Mexico. August hasn't lived up to its
climatological history as the city's wettest and second most humid month. The last
measurable rain fell a week ago -- but the last downpour-generating storms hit nearly
three weeks ago, on Aug. 4. The last 17 days have hosted only 0.06 inches of rain. The
northward rush of humid air Thursday led to eruption of scattered though impressive
thunderstorms to Chicago's south and west. Late-day Doppler radar scanned cloud
tops as high as 41,000 feet and estimated rainfall in harder hit locations just 90 miles
southwest of Chicago at 1.50 inches.
FAY'S HISTORIC RAINS NOT HISTORY YET; DELUGE SHIFTING WEST AND NORTH, AND MOVING SLOWLY
Sections of central Florida were reeling from a second day of downpours from stalled
Tropical Storm Fay. Just shy of 30 inches of rain fell in the Melbourne area. Cape
Canaveral recorded nearly 9 inches Thursday. The storm's impact is far from over. The
slow west/northwest drift threatens to spread torrential rains north into southern
Georgia and Alabama.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Rain has been in remarkably short supply in recent weeks -- hardly enough to keep up
with the 1.40 inches of water lost each week to evaporation in the warm August sun.
The last measurable rain to fall here was the 0.06 inches at O'Hare on Aug. 13. Truly
significant rain has been absent even longer. It was almost three weeks ago that a
lightning-laced thunderstorm complex unleashed driving downpours here totaling 2.43
inches at O'Hare.
Increasingly moist air will lead to noticeably higher humidities in coming days and
growing prospects that scattered thunderstorms will occur. Upper winds are to remain
comparatively light as the air's moisture content surges to nearly 2 inches. This means
any thunderstorms that develop may be capable of some heavy downpours --
especially Friday and Friday night then again later Saturday or Saturday night. Things
should dry out Sunday.
MORE RAIN FROM FAY IN MELBOURNE, FLA. THAN IN 2 HURRICANES IN 2004
Central Florida is reeling after rain of historic proportions associated with Tropical
Storm Fay. More rain has fallen in east central Florida -- 17.63" at the National Weather
Service Office in Melbourne in recent days -- than fell there in two 2004 hurricanes --
Frances and Jeanne.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Despite the brief chill at this point in the month a year ago, August is running more
than three degrees cooler this year. Even though August 2007 highs failed to reach 70
degrees on both the 18th and 19th, last summer had managed its fair share of hot
temperatures, having produced 14 days of 90-degree readings. The city a year ago
today was just two days away from a 15th day at or above 90 degrees.
The comfortable weather here Tuesday extends into a second day Wednesday, driven in
part by northeast winds off a sprawling area of high pressure centered over the Great
Lakes. The inland-moving northeast flow Tuesday provoked a few isolated
thunderstorms in Chicago's far western suburbs and in sections of northern Indiana.
DeKalb recorded 0.08 inches of rain in the storms .
TROPICAL STORM FAY DRENCHES FLORIDA WITH UP TO 10 INCHES OF WIND-DRIVEN RAIN, SEVEN TWISTERS TUESDAY
With the concern over flooding growing as Tropical Storm Fay moves off the Florida
peninsula Wednesday, where it is to tap energy and moisture off warm Atlantic waters,
residents are reeling after a day of downpours and twisters Tuesday. More than 9 inches
of rain fell near Jensen Beach on Florida's east coast.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Chicagoans are accustomed to most of their fronts and weather systems arriving from
the west. But sometimes a "back door" cold front -- one which slides across the area
from the northeast -- visits the area. Tuesday is such an occasion. The front's passage
briefly checks the string of slow but steady daily temperature increases under way here
since Saturday. Strengthening northeast winds behind the front Tuesday will lower
temperatures over much of the area into the 70s. An isolated shower or thunderstorm
may develop in a few spots west and south of the city as the gusty northeast winds
converge with slower moving air. It's a setup that forces air to rise, cool and condense.
Noticeably muggy air won't be absent long. Resurging warmth and humidity as early as
Thursday afternoon threatens to ignite clusters of thunderstorms while boosting
temperatures late this week.
WINDY POST-FRONTAL TEMPERATURE DIVE TAKES GREEN BAY FROM YEAR'S FIRST 90 TO 75 DEGREES IN AN HOUR
Temps in Green Bay went into a tailspin Monday evening as the back-door front visiting
Chicago on Tuesday passed. Readings there fell from 90 degrees -- the first 90s there
in 2008 -- to 75 in an hour. Northeast winds gusted to 31 m.p.h.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
After an auspiciously wet start, August has turned dry in the Chicago area. With nearly
3.5 inches logged in the city's official rain gauge at O'Hare International Airport
through Aug. 4, the city seemed well on its way to blow away the month's normal
4.62-inch rainfall total. However, since then, the rain spigot has abruptly turned off
with only a meager 0.06 inches on the books in the last two weeks.
Rain does not appear to be in the cards here until late Thursday, when tropical moisture
surges into the area. Should the remnants of Fay pass close to Chicago as indicated by
some computer models, the city could be in line for a resurgence of precipitation by
next weekend.
FAY'S TRACK, STRENGTH STILL IN DOUBT
As Tropical Storm Fay prepares to cross western Cuba and head into the eastern Gulf of
Mexico, its track and intensity are still in question. Fay, already responsible for five
deaths in Hispaniola, is expected to reach hurricane strength after crossing Cuba and
energizing on the bathtub-warm waters of the eastern Gulf of Mexico as it heads
toward the United States. Florida still appears a likely landfall target with hurricane
watches posted through the Keys and along much of the state's west coast.
--By Steve Kahn, WGN Weather Center Meteorologist
After six straight days with highs in the 70s, summertime 80s are back in Chicago.
Readings broke the 80-degree mark Saturday for the first time since Aug. 9 marking the
start of a warmer and eventually more humid air flow into the Midwest.
More clouds and a small chance of thunderstorms may detract from Sunday’s Air &
Water show after nearly cloudless skies and unlimited visibilities highlighted the show’s
first two days.
More thunderstorms are possible later in the week and on the weekend as a continuing
southerly flow of air feeds moisture into the region.
The increase in cloudiness along with periodic showers and thunderstorms should put a
cap on temperatures, holding afternoon highs below the 90-degree mark.
STRENGTHENING TROPICAL STORM FAY APPEARS TO BE FLORIDA-BOUND
Tropical Storm Fay, the season’s sixth named storm in the Atlantic, now packing top
winds of 45 m.p.h. , is expected to become a hurricane after crossing western Cuba on
Monday. Latest computer guidance brings the storm into the far eastern Gulf of Mexico
as it heads for a possible Florida Gulf Coast landfall on Tuesday afternoon.
Skies above Chicago Friday evening included the nearly full moon and, as Norma
Saldana of Rogers Park discovered, meteors too. While looking out over Lake Michigan,
she spotted four of them. The Perseids meteor shower, which peaked earlier this week,
may produce sightings in the Chicago area the next few nights.
The Chicago Air and Water Show opened with perfect weather Friday. The day's
78-degree high marked the area's sixth consecutive day of 70-degree temperatures --
something which last happened in August's opening two weeks 34 years ago. Only one
in five Augusts since 1928 has produced six-day strings of 70s.
New York City was placed under a tornado warning Friday, an uncommon event.
Doppler radar had indicated a circulation in thunderstorms sweeping the area. The
storms downed trees and power lines and produced structural damage. Weather Service
personnel will investigate a possible tornado touchdown near the border of the Bronx
and Westchester County Saturday.
AFTER SUMMER DOMINATED BY 90s, DENVER SHIVERS IN 50s
Snow appeared Friday near Colorado's Eisenhower Tunnel as Denver residents endured
rain and 50-degree temperatures.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Weather conditions challenged Chicago's Air & Water Show a year ago, but promise
nothing but clear sailing for the popular event that expands to three days this year.
More than an inch of rain fell on the show's second day in 2007 -- a remnant of
Tropical Storm Erin that had come ashore earlier in the week on the Texas Gulf Coast.
But sprawling high pressure will hold rain at bay this year. Friday's northeast winds will
be replaced by lighter onshore (easterly) breezes Saturday and a light west-to-
southwest flow Sunday. Temperatures warm by day to the 80s in an August running
5.3-degrees cooler than a year ago.
Several isolated but active thunderstorms swiped the Chicago area Thursday. Hardest
hit were northwest Indiana and Chicago's southwest suburbs. Schererville, Ind.,
topped area rainfall totals with .39 inch.
There's growing concern a westbound tropical system may be headed for hurricane
status in the days ahead. The system, in its infancy and churning west just north of
Haiti and the Dominican Republic on Friday, moves over energy-rich 86-degree waters
known to fuel storm intensification.
WEST BROILS WHILE PATTERN SHIFT PROMISES WARMER, MUGGIER WEATHER
HERE IN AUGUST'S FINAL WEEKS
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Unlike the storm outbreaks of recent weeks, Wednesday's thunderstorms were
selective. The heaviest of them emanated from billowy cumulus clouds that towered as
high as 42,000 feet above the Chicago area and doused a few spots with gusty
downpours. Northwest suburban Mt. Prospect recorded .90-inch in just 30 minutes and
neighboring Arlington Heights was drenched by .70 inch. In typical summer fashion,
rainfall was uneven and affected just 30 percent of the Chicago area.
Northeast winds off Lake Michigan should act to stabilize the atmosphere in Chicago
on Thursday once some early morning showers depart. But daytime heating is likely to
produce a few thunderstorms at the periphery of the inland-moving lake air -- in the
far west and southern suburbs.
A 4TH AUGUST DAY IN THE 70S FOR FIRST TIME IN 4 YEARS
Wednesday's 79-degree high marked the fourth day of 70s in Chicago. That has not
happened in August's first two weeks over the past four years.
TROPICAL FORECASTERS KEEPING CLOSE EYE ON DISTURBANCE HEADED FOR BAHAMAS
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
August is the wettest and often the muggiest month of the year. Yet, summer heat
continues in short supply, continuing a trend that has dominated much of the 21st
Century’s opening decade. There have been only 162 days 90 degrees or warmer at
Midway Airport over the period from 2000 to 2008. That’s by far the fewest 90-degree
temperatures in the opening nine years of any decade on record here since 1930.
This summer’s highest reading to date has been just 91 degrees. That’s unusual. Since
1928, only one year—2000—has failed to record a higher warm-season temperature by
Aug. 13.
FUNNEL HOVERS OVER NW INDIANA LATE TUESDAY; HURRICANE FORECASTERS MONITORING ATLANTIC SYSTEM
A pocket of cool air aloft and the additional “lift” provided as air accelerates into a
pocket of strong jet-stream winds aloft produced a funnel cloud over northwest
Indiana on Tuesday evening. The funnel, which hovered over Cedar Lake and Lowell for
nearly 10 minutes, never touched the ground and dissipated without incident.
A disturbance in the Atlantic east of the Lesser Antilles threatens to strengthen and
become the next tropical depression. It is being watched by hurricane forecasters.
Chicago's recent round of beautiful weather with unlimited visibilities and cool
temperatures -- among them the coolest highs in five weeks -- have seen overnight
lows as chilly as 49 degrees in far west suburban Rochelle and 51 degrees at nearby
DeKalb. Normal lows this time of the year are in the low 60s. As cool as those Chicago
area readings have been, minimum temperature in recent days across the North Woods
of Wisconsin have dipped to truly autumn-like levels, including 40 degrees at Ashland,
41 degrees at Merrill and 43 degrees at Superior and Antigo. The cool readings are the
product of northwest steering winds that have guided Canadian air across the Midwest.
Thunderstorms on the west side of this cool air pummeled sections of Nebraska on
Monday. They towered to 51,000 feet and unleashed nearly 5 inches of rain on Butte --
on the Nebraska/South Dakota border.
WEATHER BEING MONITORED IN THE ATLANTIC COULD BE TROPICAL TROUBLE
Two areas of disturbed weather are being monitored by tropical weather forecasters at
the National Hurricane Center. Either or both may develop into tropical depressions in
the next day or two.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
With a northwest flow aloft steering Canadian-source air into the western Great Lakes and predominantly easterly surface winds, temperatures this week look to average a little below normal. High pressure will center over Lake Michigan Monday and then edge into the eastern Great Lakes later Tuesday, where it will hold until late week. Meanwhile, low pressure in the Northern Plains will move into the upper Mississippi Valley. For Chicago, sitting on the edge of these two weather regimes, this eastward movement will mean much more cloudiness and a chance of rain as early as late Tuesday.
If computer models prove correct, a very unusual low pressure circulation aloft could drift slowly southeast in the northwesterly flow, enhancing development of a broad moisture-laden low pressure surface system that could mean a 48-hour-plus period of showers and thunderstorms for northern Illinois next weekend.
HEAVY RAINS OVER SOUTHEAST U.S.
Pushed to the Gulf Coast by the strong northwest flow aloft, a stationary front oriented west-east through the Southeast will trigger heavy rains, well in excess of 2 inches, over most of the southeastern Gulf Coast states the first half of the week.
--By Paul Dailey, WGN Weather Center Meteorologist
With the upper-level jet stream flow poised to hold out of the northwest,
Canadian-origin high pressure air masses are expected to influence Chicago's weather
into next weekend. There should be only minor day to day variations in temperatures,
averaging near or slightly below normal for this point in August. Low pressure midweek
may give a 48-hour period of unstable weather featuring periods of showers and
thunderstorms starting later Tuesday extending into Thursday. Bathers along the south
end of lake Michigan are cautioned to watch for rip currents today and Monday as north
winds build waves over the open water.
YEAR'S LONGEST 80-DEGREE-PLUS STRING ENDS SOONER THAN NORMAL
Climate records at Midway airport reveal that in a typical year at least 23 consecutive
days of 80-degree-plus highs are recorded. This past Friday's high of 79 degrees ended
a 16-day string of 80s--likely to be 2008's longest.
METEOR SHOWER SIGHTING LIKELY
According to Dan Joyce of Triton college's Cernan Earth and Space Center, 2008 Perseid
meteor shower activity will peak later Monday and early Tuesday.
Thunderstorms may flare later Saturday, developing in several clusters along a
southbound cold front that approaches this afternoon and passes with a wind shift to
the north in the evening.
Though hardly the muggy air mass that gripped the area earlier this week, the
atmosphere here will hold nearly 1.2 inches of evaporated water later Saturday. Surface
winds converging along the cold front while winds aloft diverge (move apart) signal that
thunderstorm-generating large-scale "lift" is being generated.
At the same time, faster-than-normal vertical temperature declines are to set up,
encouraging air to rise with gusto. Stronger than usual upper-level northwest steering
winds are likely to push along any thunderstorms that might erupt, increasing the
threat they'll become strong wind producers. The remnants of overnight thunderstorms
to Chicago's northwest may manage a sprinkle from mid-level clouds Saturday
morning, but the hope is most rainfall will await the front's arrival late Saturday.
CHICAGO'S 16-DAY STRING OF 80s AND 90s ENDS; COOLEST HIGH IN 2.5 WEEKS
Friday's 79-degree high may have ended this warm season's longest
80-degree-plus spell.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
As Chicagoans reveled in Thursday's picture-perfect weather, Michigan beachgoers not
more than 72 miles away were dazzled by a series of waterspouts spawned just before
noon by a southbound cluster of thunderstorms. Cool air above mid-70-degree waters
encouraged warmer, more buoyant air to rise and set the stage for the 20,000-foot-tall
thunderstorms from which as many as three waterspouts emerged just west of South
Haven, Mich., sending spray hundreds of feet into the air. The waterspouts never came
ashore, where they would have turned into tornadoes.
Chicago has lost 1 hour and 5 minutes of sunshine since June 20 -- the year's longest
day and astronomical start of summer. Seasonal loss of sunshine occurs fastest at
higher latitudes. Barrow, Alaska, will see 3.7 fewer hours of sun Friday.
ACTIVE SEASON TO DATE JUST A WARM-UP; HURRICANE FORECASTERS BOOST 2008 FORECASTS
NOAA's Climate Prediction Center, citing the active nature of the 2008 hurricane season
to date, has boosted odds of an above-normal season from 65 to 85 percent and now
predicts 14 to 18 named storms, including seven to 10 hurricanes -- three to six of
them potentially major (Category 3 with 111 m.p.h. winds or higher).
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
Northwest winds guide a series of comfortable Canadian air masses into the Midwest
over the next several weeks, all but eliminating Chicago's exposure to prolonged heat.
Surges of humid air will raise the possibility of thundery weather from time to time --
the next due here Monday into Tuesday. While predominantly dry weather occurs the
next few days, bright sun and a hint of instability in the warmer hours, minor
jet-stream disturbances and converging winds along an inland-moving lake breeze
Thursday and Friday afternoons may ignite spotty showers or t-storms. Known as
diurnal thunderstorms because they bubble into existence as temperatures rise and
low-level air becomes buoyant, they fade quickly once the sun sets.
Gusty thunderstorms swept across Lake Michigan into the area between Holland and
Grand Rapids last night behind an eye-catching shelf cloud. Similar t-storms in
southwest Wisconsin late Wednesday produced 50 m.p.h. wind gusts and 1-inch hail
near Dodgeville.
DENVER'S RECORD-BREAKING 24-DAY 90+ DEGREE STREAK ENDS -- FINALLY!
Denver -- after a record-breaking 24 consecutive days above 90 -- reported a high of
just 88 degrees Wednesday.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
It's official -- Monday evening's fast-moving squall line unleashed at least three
tornadoes as it blasted across the area with lightning displays few here will soon
forget. Twisters were behind the damage in Griffith, Ind., hit by an EF-2 (Enhanced
Fujita scale-2) intensity tornado (111-135 m.p.h.), Bloomingdale in Du Page County,
where an EF1 twister (65-85 m.p.h.) struck, and Bolingbrook in Will County, where an
EF1 tornado (86-110 m.p.h.) was reported. Until Monday's storms, August had hosted
only 23 of the 119 summer-season twisters recorded since 1950 across the 14
counties closest to Chicago from southeast Wisconsin into northwest Indiana.
The 2.43 inches of rain that accompanied Monday's storms at O'Hare pushed
meteorological summer rainfall (since June 1) nearly five inches above the 137-year
average here. The deluge makes this summer the wettest here since 1993.
THUNDEROUS 6-INCH-PLUS CLOUDBURST DRENCHES NORTHWEST INDIANA BEFORE SUNRISE TUESDAY
As the intense t-storms slowed across the southern portion of the metro area and
moved into northwest Indiana early Tuesday morning, rainfall totals increased
significantly, peaking in excess of 6 inches in and around the Valparaiso, Ind., area.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
A violent squall line swept across the Chicago area Monday evening, packing
hurricane-strength winds as high as 94 m.p.h. recorded at the Harrison-Dever Crib just
off the downtown lakefront. Fueled by hot and humid air, the storms left a trail of
downed trees, some 1 to 2 feet in diameter and power lines from northwest Illinois all
the way to Lake Michigan.
Damage was severe in Mt. Morris, where a building was leveled, and a grain bin and a
phone tower were blown down.
Several homes were damaged in Bolingbrook and a tornado was reported on the ground
in Schiller Park. The lightning display was incredible at one point, reaching 10,000
strokes in just one hour. Branches littered streets in Chicago's Wrigleyville area and
standing water flooded streets in the wake of torrential downpours.
WILTING DOWNSTATE HEAT AND HUMIDITY SENDS HEAT INDEXES OVER 115-DEGREES
Downstate weather was suffocating Monday with heat indexes reaching dangerous
levels. Alton, just east of St. Louis posted a heat index of 124 degrees, while Rantoul
reached 114 and Springfield 112.
--Steve Kahn, WGN-TV/Chicago Tribune Meteorologist
Dew points in the 70s will arrive in Chicago Monday as a saunalike air mass that has had
the Plains baking for days makes inroads into the Midwest. Highs will flirt with the
90-degree mark from the city northward as clouds and thunderstorms keep the mercury
in check, but readings should climb to the middle 90s in the far south suburbs. Heat
advisories are posted for areas south of Interstate 80 where readings in the middle and
upper 90s coupled with dew points in the 70s will produce heat indexes as high as 105
degrees.
The muggy conditions should be nothing more than a memory by Wednesday as a
refreshingly cooler and drier air mass moves in for an extended stay.
TROPICAL STORM EDOUARD DEVELOPS
Low pressure in the western Gulf of Mexico quickly intensified into Tropical Storm
Edouard Sunday afternoon with an expected Texas landfall early Tuesday, possibly as a
hurricane.
--By Steve Kahn, WGN Weather Center Meteorologist
After a warm and increasingly humid weekend, Chicago is slated for a major- league
burst of heat and humidity Monday with readings expected to reach the middle 90s—
the hottest weather so far this summer. Before the heat moves in Monday afternoon,
the city may have to deal with several bouts of showers and thunderstorms that could
dump some heavy rainfall here mainly Sunday night and early Monday.
Once the heat arrives on gusty southwest winds, readings should quickly surge into
the middle 90s, and, combined with a dose of Gulf Coast-level humidity, heat
indexes could approach 100 to 105. So far this summer the city has not seen a
temperature higher than 91 degrees, something that has only happened twice in 80
years at Midway Airport: first in 1979 and again in 2000.
The heat should quickly retreat as cooler northeast winds set in by Wednesday and
dominate through the rest of the week.
DENVER SHATTERS MORE HEAT RECORDS
A 130-year-old high-temperature record fell in Denver Saturday, when the mercury
hit 103 degrees, besting the old record of 100 recorded in 1878. Denver has logged
an unprecedented 21 consecutive 90-degree-plus days, with more expected. The
city’s previous string of 90s was 18 in 1878 and 1901.
A succession of downpour- and small- hail-producing thunderstorms erupted along an
inland-moving lake breeze Friday in southern Cook County, then swept into and across
northern Indiana. Winds converge at ground level along such lake- breeze fronts,
allowing air no recourse but to ascend in humid columns of air. The towering
thunderheads produced through this process -- referred to as cumulonimbus clouds
by meteorologists -- are often spectacular in appearance, taking on the form of
cottony masses within which lightning can be seen flashing. One of the storms
produced 0.60 inches of rain in just 10 minutes in Ft. Wayne, Ind.
Saturday will be rain-free -- cooled by north-to-northeast winds that import
noticeably drier air from Canada. Heat will begin to make inroads here Sunday, but will
likely be tempered by storm outflows.
BLAZING HEAT OVER 13 STATES REACHES
CHICAGO MONDAY INTO TUESDAY
High-temperature records fell in six states Friday, led by 104-degree highs in both
Denver and Miles City, Mont.
Excessive-heat advisories are posted for Saturday across 13 states from Montana to
Texas as an expanding western heat dome spreads into Chicago, bringing this
summer's hottest weather by Monday.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune
