September 2007 Archives

In yet another demonstration of the truism that the weather does not read the calendar, Chicagoans will enjoy another week of summer temperatures in the autumn. The average of daily high and low temperatures from today through Oct. 7 is expected to be 68 degrees, and that is 11 degrees above the climatological normal for that period. The city's daily highs are forecast to reach or exceed 80 degrees on four of the next six days -- a significant contrast to the long-term historical expectation that only one day in eight climbs to that level in early October. Thunderstorms, too, will be rumbling across the city area this week with a frequency more typical of July than October. A parade of disturbances sweeping across the Upper Midwest (similar to the system that spawned Sunday night's storms) will trigger storms about every three days -- late Tuesday into Wednesday and again late Saturday.
--By Richard Koeneman, WGN Weather Center Meteorologist

At midnight tonight, September enters the record books as one of Chicago's warmest, sunniest, and driest in recent years. And summer refuses to let go, because October will begin where September left off. Afternoon temperatures in the 70s and 80s are projected right through the upcoming week.
Computer models indicate the jet stream and major storm track will remain well to the north, approximately along the Canadian border, and southerly wind flow will be the dominant factor in Midwest weather for several days. That keeps Chicago's afternoon high temperatures 7-16 degrees above the upper 60s that are typical at this time of the year.
September's exceptionally sparse precipitation totaled barely more than an inch -- only one-third of normal -- but that might improve in October. Several opportunities for showers and thunderstorms may present themselves, especially with a pattern change 6-8 days from now.
--By Richard Koeneman, WGN Weather Center Meteorologist

Chicago weather historian Frank Wachowski provides these preliminary weather statistics for September 2007: With 76 percent of possible sunshine (versus a normal of 62 percent), it will enter the record books as Chicago's sunniest month in three years (sunniest since, coincidentally, September of 2004, which registered 90 percent of possible sun).
With an average temperature of 68.2 degrees (4.4 degrees above normal), this becomes the fifth warmest September since temperature observations began at O'Hare Airport in 1959.
Finally, September delivered 1.09 inches of rain -- only one-third of the normal monthly total of 3.27 inches.
And the warm temperature regime continues. Chicago's afternoon readings are forecast to reach or exceed 80 degrees on four of the next six days, but the climatological expectation in early October is only one day out of six.
A few thunderstorms are possible late Sunday and again late Tuesday.
--By Richard Koeneman, WGN Weather Center Meteorologist

An enduring characteristic of Chicago’s vigorous temperature climate is its tendency to reach for the extremes, and that’s what lies immediately ahead. It will be a pleasurable experience this time around, because unseasonable daytime warmth is anticipated.
Strengthening southwesterly winds, surface and aloft, will dominate Chicago’s weather through most of the upcoming week. Today’s high temperature in the lower 70s is likely to be the coolest day by far of the next six. Expected high temperatures averaged over the week beginning today (Sept. 28-Oct. 4) is 79º, almost 11º above normal, and a temperature level that ranks among the five warmest such periods in 136 years of Chicago temperature history.
Those expected daily temps won’t challenge daily record highs—those are in the 90s—but the persistent warmth will take the week’s average high temperature into near-record territory.
--By Richard Koeneman, WGN Weather Center Meteorologist

Meteorologists love to describe temperatures in terms of “departures from normal.” They will say, “Yesterday’s high was 69º, and that was one degree below normal.” (And that actually was Tuesday’s departure from normal, as officially measured at O’Hare.)
What’s left unsaid, however, is that a “normal” temperature is the 30-year average derived from the period 1971-2000, and that it is quite unusual for a day’s temperature to be right at “normal.” It’s even more unusual for two days to run at or near normal, but that is the pattern in which Chicago will find itself today and again Friday.
Chicago’s temps usually spend most of their time bouncing from well above normal to well below, and back again. Today’s “near normal” pattern breaks down over the weekend, when a warming trend sends readings to the upper 70s (9º above normal) and into the lower 80s (14º above) by this coming Tuesday.
--By Richard Koeneman, WGN Weather Center Meteorologist

Severe thunderstorms blasted across metropolitan Chicago Tuesday afternoon and evening, but they were a hit-or-miss affair. Damaging winds and blinding rains struck a few locations, whereas residents in other spots bypassed by the storms were left wondering what the fuss was all about.
High winds left several buildings in Elgin (35 miles west of the Loop) with structural damage, and Gary, Ind., reported a gust to 60 m.p.h. Other locations experienced only moderate winds. Rainfall also varied widely, and that is typical of thunderstorm precipitation. West suburban Oak Brook recorded 1.13 inches of rain in 20 minutes around 3 p.m., but a sprinkle barely dampened the ground at Midway Airport.
Tuesday’s strong thunderstorms and 85° temperatures preceded the arrival of much cooler Canadian air that will dominate the local weather scene for several days.
--By Richard Koeneman, WGN Weather Center Meteorologist

Photo by Scott Korogodsky

Thanks to Scott Korogodsky for taking this great shot of a rainbow over Dolphin Stadium in Miami very early in tonight's game between the Cubs and the Florida Marlins.

It’s an ideal brew for strong thunderstorms across the Midwest: A vigorous jet stream aloft and a strong cold front advancing into warm, humid air. The Storm Prediction Center indicates the possibility of severe t-storms here and elsewhere in the Midwest.
Yesterday’s warmth sent Chicago’s temperature to an official high of 90º at O’Hare (one degree shy of the record for the day) and to 91º at Midway (which established a new, though unofficial, daily record high at that station). Kankakee registered the area’s hot spot, with 95º.
Proving that some good can come from just about any kind of weather, the recent long stretch of dry days has advanced Illinois crop harvests. WGN’s AgriBusiness broadcaster Max Armstrong says the Illinois corn and soybean harvests are running well ahead of normal. However, August’s heavy rains and flooded fields have devastated area pumpkin production.
--By Richard Koeneman, WGN Weather Center Meteorologist

Borne in by gusty southerly winds strong enough to overcome the cooling influence of Lake Michigan, warm air surging across Chicagoland today will send afternoon temperatures well into the upper 80s.
This is the ground-level effect of a powerful jet stream whose 90-m.p.h. winds (at an elevation of 45,000 feet) are blasting in a corridor from Oklahoma to Lake Superior. Chicago's expected high temperature in the upper 80s puts the thermometer within shooting distance of the record high for the date, 91 degrees, registered 116 years ago (1891). The amount of temperature-lowering daytime cloudiness is an important consideration. Gathering afternoon clouds may cap area temperatures in the mid 80s, whereas a sunny afternoon would permit a run at the day's record.
Powerful thunderstorms that rattled across the Northern Plains late Sunday will develop again today, and remnants of those storms arrive here by Tuesday.
--By Richard Koeneman, WGN Weather Center Meteorologist

Geographer Dr. George Kimble once observed that, weatherwise, “September is a month of many virtues and few vices.”
Many Chicagoans might find Kimble’s generalization overly optimistic, but few will contest the splendid weather that the city is experiencing this weekend. Saturday’s sunny sky and temperatures in the 70s as well as Sunday’s readings in the 80s provide a perfect setting for outdoor activities.
However, late September has also delivered genuinely nasty weather in years past in other places. The temperature plunged to -9ºF at Yellowstone National Park on Sept. 24, 1926, and widespread freezing readings caused huge crop losses from Washington to Montana. A rare West Coast hurricane moved onshore south of Los Angeles on Sept. 25, 1939.
Finally, large hail killed several hundred Canada geese in Wisconsin’s Horicon Marsh on Sept. 30, 1993.
--By Richard Koeneman, WGN Weather Center Meteorologist

Chicago area temperatures hit rarified heights Friday afternoon, with most locations recording highs in the upper 80s to lower 90s. Highest readings included 93 degrees at Kankakee and 91 degrees at Northerly Island. Midway's 90 degrees was only the 4th time this figure was reached on Sept. 21 in 80 years of weather records at that site.
However, Chicagoans will experience significantly cooler and less humid conditions today as Canadian high pressure pushes into the area. The impact of this high will be short-lived as it quickly moves east. Strong warming southerly flow up the backside of that high reaches into Illinois Monday. The best chance of thunderstorms next week will most likely be Monday night and Tuesday, preceding and accompanying a vigorous cold front.
Tornadoes were associated with a low pressure system along the northern Gulf Coast Friday night, with heavy rains and flooding expected as it moves into southern Mississippi today.
--By Richard Koeneman, WGN Weather Center Meteorologist

On today’s date, the “Great New England Hurricane of 1938” smashed without warning across a portion of the nation that rarely experiences such storms: New England. The tropical cyclone grazed Cape Hatteras, N.C., about 3 a.m. on Sept. 21 and, from there, Weather Bureau forecasters believed the hurricane was headed northeast into the Atlantic Ocean, as such storms typically do. This was in the days before aircraft reconnaissance, weather radar or satellite surveillance. Unrealized by the forecasters, the hurricane instead accelerated north at 50-60 m.p.h.—the highest forward speed a hurricane has ever attained—and blasted with Category 3 intensity (winds 111-130 m.p.h.) across Long Island, N.Y., and into Rhode Island and surrounding areas by early afternoon. The sun had been shining only two hours earlier. Winds and storm surge claimed nearly 600 lives, and left New England in a shambles.
--By Richard Koeneman, WGN Weather Center Meteorologist

Wednesday marked the seventh time this month temperatures here have surged to 84° or higher. The 84° high at both Midway and O’Hare and the 87° reading at Northerly Island were 29° warmer than the chilly 55° high a year ago. It was so cool in September a year ago, the month’s warmest reading never even reached Wednesday’s levels, peaking just once at 83° on Sept. 8 and reaching or exceeding 80° in 2006 only four times all month! By contrast, there have been eleven 80°+ days this September.
Easterly winds off Lake Michigan lower temperatures Thursday—but only modestly. Strong southerly winds send readings back to the upper 80s Friday.
North Floridians dealt with high winds and waves of heavy rain a third day Wednesday. Rainfall at Daytona Beach had reached 4.21” by late evening—a new record—while Jacksonville Beach’s rain tally since Monday soared to 10.31”.
--By Tom Skilling, WGN-TV Chief Meteorologist

Even with autumn’s official start less than 5 days away, summer weather was back in all its glory Tuesday. Temperatures soared to 90° at Midway Airport and Chicago’s lakefront and reached 91° at Gary and Kankakee. O’Hare’s 88° official high was 15° above normal and occurred two weeks beyond the average last date for an 88° high at the site, which is Sept. 5. Suburban residents, who only four days earlier had scraped an unseasonably early frost off cars, joined others across the metro area in marking July-level temperatures, including the city’s latest 90° temperature in 7 years at Midway Airport.
The atmospheric demarcation between Chicago’s warmth and much cooler air to the west grew stormy late Tuesday. T-storms whipped sections of Iowa with 60-70 m.p.h. wind gusts. The storms were predicted to weaken as they crossed the Mississippi, arriving in Chicago early Wednesday as patches of leftover cloudiness.
--By Tom Skilling, WGN-TV Chief Meteorologist

Our friend Mark Vogan e-mails these images from Scotland showing the frost which coated a number of outdoor surfaces early Tuesday morning. Mark writes:

“The forecast last night suggested a frosty night here with lows dropping to around freezing, so I got up and took the car for a drive down to the canal here in Kirkintilloch before sunrise to look at the steam rise off the warm waters of the canal. The temp at 5.50am was about 32F and frost coasted cars and house roofing. Skies cleared overnight and with no wind, the old radiational cooling kicked in. A pretty decent frost for mid-September, certainly can't remember the last time we had a decent frost this early. Perhaps in years gone by when winters where "real winter". In fact Tom we has mornings in January where it was warmer than this morning!”

It’s always great hearing from you, Mark, and thanks for the report! It certainly shows that this Sunday’s autumnal equinox is fast approaching!

Tom Skilling

Photo courtesy: Mark Vogan

The area is in the midst of a remarkable 4-day temperature resurgence likely to rank among the four largest here in September. On only four occasions since Chicago weather records began in 1871 have September temperatures rebounded 50°+ in a span of four days. A high of 89° or warmer Tuesday coming off Saturday morning’s record breaking 39°—the coldest temp. to occur here this early in 117 years—would make this the fifth. Tuesday’s powerful winds, blowing from the southwest all the way from the ground tens of thousands of feet aloft into the jet stream, boost the odds of this happening. A high of 90° would mark the Chicago area’s latest such reading in 7 years. The 51° increase over Saturday’s 39° low would be the largest September temp increase in 54 years.
Powerful storms swept sections of Florida Monday producing brief tornado touchdowns, offshore waterspouts and torrential downpours.
--By Tom Skilling, WGN-TV Chief Meteorologist

Just two mornings ago, many Chicagoans were cranking up the furnace as the city experienced a record-setting 39 degree low—the earliest sub-40-degree fall reading here in 117 years. Today's high, expected to top out in the lower 80s, would constitute a remarkable 43-degree temperature rise. But if Tuesday afternoon's max temperatures reach the anticipated hot weather 90 degree benchmark, it would complete a remarkable 51-degree increase -- one of the largest ever recorded here in September. If the mercury does reach 90 degrees Tuesday, it would mark the 19th and possibly last such occurrence of 2007 as the city rapidly approaches the end of its hot weather season.
Severe thunderstorms raked southwest Florida Sunday evening. At least one tornado struck the Fort Myers/Cape Coral area, damaging several homes and peeling the roof off of a retail building. Hail pelted the area as high winds uprooted several trees and knocked out power.
--By Steve Kahn, WGN Weather Center Meteorologist

Autumn paid an early visit to much of the Midwest Saturday as a multitude of temperature records fell by the wayside. The city’s official 39º record low at O’Hare not only broke the old record of 40º for Sept. 15 set in 1985, but it was also the city’s earliest in the season sub-40º reading in 117 years since a 39º low on Sept. 13, 1890. Some other record lows set at nearby locales included Rockford (35º), Springfield (35º), Moline (36º) and Madison (32º). Just to the west, both Cedar Rapids (31º) and Dubuque (32º) experienced their earliest freezes on record.
The brief chill will soon be forgotten as a vigorous warm-up is likely to boost temperatures more than 50º over the next few days to highs tickling the 90º mark by Tuesday. The rest of the week also promises to be warm with readings fluctuating through the 80s on most days.
--By Steve Kahn, WGN Weather Center Meteorologist

It's not common for such chilly air to hit this early. Saturday morning's predicted 39 degrees at O'Hare didn’t occur a year ago until Sept. 29 at the site -- that's two weeks later than today -- and has occurred on average on or about Oct. 3 over the past 136 years. The 39 degree low would set a new record for the date, breaking the old record of 40 degrees set 22 years ago in 1985.
Diminishing winds have produced the area's most dramatic cooling from the Fox Valley and McHenry County westward. It's a development which has favored frost formation in some west suburban locations. In stark contrast, the same chilly air's interaction with still-warm Lake Michigan waters has led to lake-effect clouds east of Chicago and threatens light rain showers from sections of LaPorte County eastward.
Northern Minnesota was home to the Midwest's first flurries of the season Friday, near International Falls and in the state's Arrowhead region. Chilly air produced a 22 degree low at Williston, N.D., early Friday.
--By Tom Skilling, WGN-TV Chief Meteorologist

The fall colors are out across northern Wisconsin and are likely to get better in the weeks ahead. Dan Hanson of northwest Wisconsin’s Winter, located in Sawyer County, shares these photos of the emerging colors taken Friday. The region was under frost and freeze advisories which run into Saturday morning. Thanks for the update and great photos, Dan!
--By Tom Skilling, WGN-TV Chief Meteorologist

Photos courtesy of Dan Hanson

An unusually potent early season cool spell, which is being forced south into the U.S. from the Canadian arctic by powerful northerly upper air winds, threatens to break a 22 year old record by producing a 39° low Saturday at O’Hare. The old record is 40° set in 1985. The incoming air mass is to become so unstable later today—e.g. temperatures within it are to decline so rapidly with height—that the sunshine predicted to follow daybreak clouds and showers is likely to encourage air to rise and cool producing new clouds and light showers by mid/late afternoon. Once the new overcast is in place, the day’s gusty NW winds import chilly air allowing temps to fall to the mid 50s by evening.
Winds diminish and skies clear overnight allowing temps to dive. Far west and NW suburban lows reach 33° by morning threatening the season’s first frost patches. The urban heat island is to modify cooling in the city enough to discourage frost.
--By Tom Skilling, WGN-TV Chief Meteorologist

Fall was definitely in the air Wednesday. Chicago’s 67° high was the city’s coolest temperature in 3 months—since 64° on June 5. The official daybreak low of 46° just missed the 1955 record of 44° for the date. But across the North Woods—i.e. northern Wisconsin and Minnesota—the chill broke long-standing records, several a half-century old. Rice Lake, Wisconsin bottomed out at 34° while Rice Lake, Minnesota’s temperature reached a bone-chilling 23°. Lows of 28° and 29° at International Falls and Duluth early Wednesday—both in Minnesota—broke records dating back to 1975 and 1955 respectively.
The 2007 hurricane season’s 8th named storm developed quickly Wednesday 60 miles south/southwest to Galveston, Texas, fueled by near bathtub-warm mid-80° Gulf of Mexico waters. WeatherBug sensors mounted on oil rigs 30 miles offshore clocked wind of 59 m.p.h. while measuring 4+” of rain.

-By Tom Skilling, WGN-TV Chief Meteorologist

Powerful northwest steering winds at jet stream levels aloft—between 10,000 and 40,000 ft.—have delivered a healthy early autumn chill to the area with impressive speed over just the past few days. Freezing temperatures predicted overnight across northern Wisconsin and Minnesota were expected to bring the 2007 growing season to an end. A growing season is defined as the period between the last freezing temp of spring and the first 32° reading of autumn.
While hardly chilly enough to support frost, Chicagoans haven’t escaped the cool air either. Area residents find daybreak temperatures flirting with the 1955 record low of 44°. Readings are to recover a bit to 65° beneath Wednesday’s sunny skies. But, that reading is cool for the season, 10° below normal.
Cool as it is now, highs hold to the low 60s Saturday after near record daybreak lows around 40°. The weekend is to be this area’s chilliest since mid-April.
--By Tom Skilling, WGN-TV Chief Meteorologist

Fall comes to southern Wisconsin; leaves turning and already falling
Gary Gross of Valparaiso, Indiana forwards us this picture from his aunt who lives in Madison, Wisconsin and says she's noticing color in the leaves there already. Gary says that even in Valparaiso, the seasonal color change is beginning and he notes that a number of trees' leaves are yellow along I-65 heading south to Lafayette, Indiana. Thanks for the photo and the autumn color update, Gary!

Tom Skilling

Photo courtesy: Gary Gross

As those of you who visit our weather blog know, we typically post photos from recent events. But, these photographs of spectacular thunderstorm debris clouds over the Champaign/Urbana area taken back on Tuesday, August 14 just arrived from Kevin Merrifield who took them and we wanted to share these with you. Kevin, Web Administrator at the Illinois State Water Survey Survey, tells us he was getting ready to drive to work when he spotted the clouds he appropriately describes as “eerie” approaching. He was awestruck by their appearance for obvious reasons, grabbed his camera and began photographing them. The clouds, wind tossed and mid-level (primarily altocumulus and altostratus clouds), were actually leftovers or “debris” from powerful thunderstorms which had swept areas of the Midwest farther to the north—including sections of Minnesota, Wisconsin and northern Illinois. Check these out—and many thanks to Kevin Merrifield for sharing these with us! Say hello to all of your colleagues down at the Illinois State Water Survey for us!

-Tom Skilling

Photo courtesy: Kevin Merrifield

In this photo forwarded to us by Amy Biancofiori, Jill Bulliner photographed a hummingbird while she was sitting on her porch. What became clear to Jill only after snapping this photo, was that the the hummingbird ended up framed in her photograph against the American flag. Jill thinks this an especially significant photo as we mark the anniversary of September 11. Thanks to both Amy and Jill for sending it along to us.

Tom Skilling

Photo courtesy: Jill Bulliner

Chicagoans who ventured in comfort out for lunch without a jacket Monday faced quite a surprise by the evening rush hour. Northeast winds had strengthened and inside a span of just 5 hours, temps had plunged nearly 15° into the 50s—the lowest evening temperatures here since early June. The pullback was especially dramatic in the northern suburbs where Lake County’s Libertyville, Lincolnshire, Mundelein and Lake Villa reported evening readings of only 52°. A temperature at that level equals typical highs here in early November and was cooler than the readings observed at the same time across most sections of Alaska’s arctic coast eastward into Canada’s Yukon Territory.
A second cold front passes around midday Tuesday and reinforces the chill. NW winds behind that front are to blow at 40 m.p.h. just above ground level raising the possibility some of that wind energy will “mix” down to the surface as powerful gusts.
--By Tom Skilling, WGN-TV Chief Meteorologist

Eight of September's opening nine days here have been warm with highs of 80 degrees or higher, including one official 90 degrees on Sept. 5. All that is going to change later this week as the mercury is expected to embark on a decidedly downhill trend. After fluctuating through the 70s much of this week, a slug of chilly air will descend into the Midwest on Friday, bringing a reminder of autumn's inevitable advance. Highs should peak in the upper 60s Friday, with Saturday looking especially chilly as readings struggle to reach the low 60s.
Tropical Storm Gabrielle is heading out to sea after lashing eastern North Carolina with 50 m.p.h. wind gusts, high waves and dangerous rip currents Sunday. The NOAA buoy located southeast of Cape Hatteras measured 15-foot waves, and 5.50" of rain soaked coastal Morehead City. However, the storm produced minimal damage, and much of the drought-stricken Tar Heel state missed out on what would have been a welcome rainfall.
--By Steve Kahn, WGN Weather Center Meteorologist

After last week’s bout with warm and muggy weather, cooler and less humid conditions will be making inroads into the Chicago area much of the upcoming week. The week’s warmest days will feature temps struggling to crack the 80º mark in contrast to last week’s peaks around 90º. Monday promises to be cool and showery, and by next weekend, a second and stronger surge of chilly air will raise the prospects for consecutive days with sub-70º highs and sub-50º lows. While heavy precipitation is not expected here, several periods of light nuisance-type showers may fall from the often cloud-dominated skies.
Tropical Storm Gabrielle threatens a windy and rainy Sunday for the coastal North Carolina. The storm is expected to pound the coast with heavy rains and 50 m.p.h. winds before it turns northeast and tracks just south of the Canadian Maritime provinces by mid-week.
--By Steve Kahn, WGN-TV Meteorologist

Chicagoans haven't experienced a more humid summer here since 2002. Since June, dew points, a measure of atmospheric moisture, have reached or exceeded the 70-degree level on 35 days -- 20 of them in August alone. Muggy air masses often feature dew points of 70-degrees-plus, which is why readings at that level have become the benchmark measurement in characterizing an air mass as humid. The last summer with more 70-degree-plus dew points was 2002 with 51 days. Friday's humid air provoked selective downpours, one of which swamped Midway Airport beginning at 10 a.m. with 0.90" in just 15 minutes. The site finished the day with a 1.09" tally. The WeatherBug rain sensor at Whitney Young High School reported the area's heaviest tally: 1.26".
After meandering for days several hundred miles off the Carolinas, west/northwest-bound subtropical storm Gabrielle was christened late Friday evening. Tropical storm watches were issued for the Carolina coasts.
--By Tom Skilling, WGN-TV Chief Meteorologist

All the meteorological ingredients for thundery downpours are in place Friday. Powerful wind gusts are a threat as well. Winds are converging along an incoming cold front, a set-up which encourages air to “pileup” —leaving it no place to go but up. This vigorous ascension of air creates cumulonimbus clouds or -thunderheads—the tallest clouds on earth. The ability of such formidable mounds of cloudiness to completely block incoming daylight is why skies darken so ominously as t-storms approach. Friday’s muggy, 70° dew point air is to fuel concentrated downpours which threaten to force 40-50 m.p.h. winds blowing just above the surface to crash to earth as powerful storm gusts. Local 1” rainfalls are a possibility.
Seasonably cool air takes up residence this weekend. Several fast-moving disturbances sweep across the area Saturday and Sunday nights, which is when any weekend showers will occur.
--By Tom Skilling, WGN-TV Chief Meteorologist

The scattering of northeastbound thunderstorms has led to brief downpours Thursday afternoon and evening and this rainbow photographed by Tracey Surface over Chicago’s Montrose Harbor. Great shot! Thanks Tracey!

Tom Skilling


Photo courtesy of Tracey Surface

Ted Ballou of Northwestern University Medical School’s Department of Physiology forwards us this intriguing photo. He tells us:

“Waiting for a bus on Clinton a couple of weeks ago (about 8:20 am on August 9) I looked up and to the east and saw a remarkable sight: a shadow off the Sears Tower on overhead clouds, illuminated by the rising sun in a clear eastern sky. The dark bulk on the right is the northern edge of Union Station. Cool, huh?”

Cool indeed! Many thanks for calling this to our attention, Ted!

Tom Skilling

Photo courtesy: Ted Ballou

The muggy, haze-filled atmosphere which greets Chicagoans Thursday is the most humid here in nearly two weeks. It is literally dripping with tropical moisture and has been swept north off the Gulf of Mexico by well-organized southerly winds blowing over nearly 2,000 miles of terrain—from the Gulf north to Canada’s James Bay. Computer moisture profiles Thursday indicate a deep layer of the air mass is in a state of near saturation—i.e. holding nearly all the moisture it can—extending from the ground to heights of more than 19,000 ft. Showers erupt with regularity in this sort of environment and any breaks for even modest spells of passing sun are likely to produce enough heating to encourage t-storm development.
Late Wednesday’s spotty but gusty t-storms towered to 31,000 ft. tall and produced brief downpours and 40+ m.p.h. winds. Better organized thunderstorms arrive Friday.
--By Tom Skilling, WGN-TV Chief Meteorologist

Robert Guico of Carol Stream was kind enough to share this spectacular triple rainbow photograph he took while traveling Alaska’s Denali Highway this past Thursday (8/30/2007). The rainbow occurred at the periphery of a thunderstorm which was in progress as the photo was snapped on the Denali Highway. Robert tells us:

“The low light angle creates many opportunities for unique rainbows in Alaska with the rain that does fall.”

Thanks for sharing this beautiful shot with us! I must add that Robert closed his e-mail to us saying… “We're already looking forward to our next trip.”

Alaska is definitely one of those spectacular places on this planet to which many return time and time again!

Tom Skilling

Photo courtesy: Robert Guico

Wednesday’s predicted 90° high may be among the final 90° temps of the year here. In 137 years of weather observations, Sept. 5 has been the average date of the city’s final 90° high. But, averages smooth out the exceptions. The latest recorded 90° temperature in Chicago—94° to be precise—waited until October 6, 1963 to occur. It’s worth noting that since 1928, on 124 occasions there have been 91° or higher readings logged beyond this date at Midway. A 90°+ temp Wednesday would mark the 18th time this year that the mercury at Midway and O’Hare has reached or exceeded that hot weather benchmark.
With Lake Superior teetering just an inch from its record low for this time of year and less than a foot from its all time record low set in April 1926, Tuesday’s deluge across Michigan’s Upper Peninsula is noteworthy. Marquette recorded 4.40” of rain-—the biggest tally on a single calendar day in more than four decades of records there.
-By Tom Skilling, WGN-TV Chief Meteorologist

The sun-filled holiday weather of the past weekend spills over into the work week. Monday's 88 degree high at O'Hare and 89 degrees at Midway made it the warmest Labor Day here since a 95 degree high 24 years ago in 1983. Just a year ago, Chicago's Labor Day high was only 71 degrees.
The metro area is in the midst of its longest rain-free spell since early June. But, with all the sunshine Tuesday, the first day of school for thousands across the Chicago area promises to be a very warm one as temperatures flirt with 90 degrees. Readings that warm -- while not unheard of -- become increasingly scarce this late in the season. Only 8 percent of Chicago's 90s since weather records began here have occurred Sept. 4 or later.
Nicaragua and Honduras appear headed for a punishing blow early Tuesday from compact but potentially deadly Hurricane Felix. With hurricane-force winds which cover only a third the area of 2005's Katrina, Felix is one of only nine hurricanes to follow such a southerly track.
--By Tom Skilling, WGN-TV Chief Meteorologist

As sunny skies and light winds prevail over northeast Illinois today, Hurricane Felix will be moving west-northwest through the Caribbean, toting sustained winds in excess of 165 m.p.h. Fortunately, Felix is over water -- but unfortunately the warm waters provide additional energy to the expanding storm, allowing it to pose an ever-increasing threat.
By Friday, driven by a strong upper-air low pressure trough, a cold front preceded by showers and thunderstorms will be approaching Chicago from the northwest. At the same time, the southern extremity of this upper-air troughing pattern will be over Texas and northern Mexico, influencing the direction Felix will take as it approaches the coastline of northeast Mexico.
Next weekend could see the coldest air of this new fall season penetrate south of the Ohio River.
Meanwhile, rainfall totals up to 15 inches were reported this past weekend along the South Carolina-Georgia coastline.
--By Paul Dailey, WGN Weather Center Meteorologist

Southerly winds on the back side of nearly stationary high pressure centered over the east coast of the U.S. will keep Chicago’s high temperatures well into the 80s through mid week. The Labor Day weekend will feature rain-free sunny warm days and clear mild nights. Humidity will begin to increase significantly Tuesday and Wednesday. The approach of a slow-moving cold front Thursday will trigger an extended period of showers and thunderstorms that could last through Friday night, before cooler Canadian high pressure follows next weekend.
As Hurricane Felix moves west over the warm waters of the Central Caribbean, it is expected to intensify to 125 m.p.h. maximum winds, Cat. 3, before landfall (current forecast targets the Yucatan peninsula again) Wednesday. Saturday the Savannah, Ga. area experienced significant flooding when deluged with a foot of rain.
--By Paul Dailey, WGN Weather Center Meteorologist

September and meteorological autumn 2007 open sun-filled Saturday -- but with a hint of autumn evident in the morning's cool first hours. The chill fades quickly and is followed by slow warming in coming days.
The sunshine is a welcome change of pace after a meteorological summer period which ranked among the four cloudiest of the past 10 years, according to Midway Airport weather observer Frank Wachowski. While Chicagoans basked in 100% of Friday’s possible sunshine -- the first completely sunny day in the metro area in a month -- the June-August period managed just 62% of its possible sun -- below the 67% considered normal.
Weekend swimmers in Lake Michigan will find shoreline water temperatures 14 degrees off the summer's 81° peak. But, they may be surprised, given all the rain which has fallen in recent weeks, to find lake waters 2" below levels a month ago and 4" lower than the same time last year.
--By Tom Skilling, WGN-TV Chief Meteorologist