May 2007 Archives

The books close on Chicago’s warmest May in 9 years Thursday night with the month posting a near 5° surplus. May’s daytime highs here have included six afternoon temperatures of 88° or higher—the greatest number of such readings in any May over the past 16 years. But, warm as it’s been here, temperatures pale in comparison to a record-breaking early season heat wave which has been underway the better part of the past week over a huge swath of Russia. The region between the Caspian and Black Seas registered temps just shy of 100° Wednesday while to the north in sections of Moscow, readings soared to 94°, easily surpassing May’s previous all time record of 89° set in 1891. The city is well on its way to the first set of five consecutive 90° temps in May since 1879. Moscow’s “normal” high this time of year is 68°.
A new wave of flooding rains swamped the Plains and western Midwest Wednesday—including 3.78” at Worthington, Minn.
---By Tom Skilling, WGN-TV Chief Meteorologist

--By Tom Skilling, WGN-TV Chief Meteorologist

Significant rains appear a possibility by the coming weekend for a section of the country desperately in need of moisture—but also for a region which has received too much rain in recent months. Parts of wildfire-scarred Florida, where rainfall deficits since March 1 exceed 6" in many locations, could be in line for beneficial downpours. A jet stream, well south of its normal location, sets the stage for rain development. This sub-tropical jet is to begin lifting humid Caribbean air east of Mexico’s Yucatan Peninsula in coming days, lowering barometric pressures and producing t-storms in the process. The disturbance which results is to drift north across Florida late this week into the coming weekend. Though computer rainfall projections tend to over-forecast rain in full-blown drought situations like Florida’s, the region’s abundance of warm ocean water increases the odds of the rain actually occurring. Rainfall won’t extend to all sections of the parched state, but some projections suggest local 4"+ totals aren’t out of the question.
--By Tom Skilling, WGN-TV Chief Meteorologist

May, with 80s predicted each of the remaining three days, is on its way to becoming Chicago’s most prolific 80° producer in 16 years. The month ranks 19th warmest of all Mays on record since 1871. And, by the time the books close on May 2007 at midnight Thursday, the month will have logged 14 days at or above 80°. Only six had occurred through all of May a year ago. That’s less than half as many. Not since the 16 days of 80°-plus temperatures in 1991 has a May logged as many.
This May’s average temperature of 62.7° is running well ahead of the long-term average (57.9°) and is nearly 5 degrees warmer than the same period a year ago.
Last year’s May 1-28 temperatures averaged 57.9°, which coincidentally equalled the long-term May 1-28 average here dating back to 1871.
Yesterday’s 79° high at O’Hare Airport fell short of the 91° on Memorial Day a year ago. However, sunshine was generous and showers were very spotty.
--By Tom Skilling, WGN-TV Chief Meteorologist

A warm front surges back north through the Chicago metro area later today. Warm humid southerly flow follows on its heels Tuesday with temperatures climbing well into the 80s. With the approach of a cold front from the west Wednesday, gusty south winds will maintain high temperatures and significantly increase the chance of thunderstorms, some of which could be strong. The passing of the cold front will mark a definitive change in the upper air pattern. Starting Thursday, the western Great Lakes will come increasingly under the influence of a cut-off low pressure system aloft. A low pressure circulation breaks off from the primary jet stream flow far to the north across central Canada, drifting south and east and paralleling the U.S./Canada border. This will result in mostly cloudy skies and periodic, mostly daytime, showers over northeast Illinois. At the same time, this pattern will be responsible for strong warming over the western and eastern U.S.
--By Paul Dailey, WGN Weather Center Meteorologist

Rainfall had been sparse this month with most of the metropolitan area tallying less than one inch of rain through May’s first 25 days. Unfortunately it took a holiday weekend to begin to reverse this dry trend. Booming thunderstorms swept the northern suburbs early Saturday bringing upwards of an inch of rain to portions of that area. More rain fell there Saturday afternoon and evening, while vigorous thunderstorms brought downpours to the South Side and southern suburbs, areas bypassed by the Saturday morning storms. Rain fell heavily in the Joliet area Saturday afternoon bringing flash flooding to many spots. The rain should end here early Sunday and is not expected to return until late Monday allowing many dry hours for holiday activities.
Chicago’s rain paled to the flooding cloudbursts that struck Texas Saturday. Victoria was doused by 4.41”, while 3.29” soaked Waco.
--By Steve Kahn, WGN Weather Center Meteorologist

Rough weather could threaten portions of the Chicago area late Saturday, a development which may trigger severe weather. The new, more powerful late-day storms would follow the lingering showers and thunderstorms Saturday morning. Those rains are part of a disturbance that walloped south-central Missouri with nearly 5” of rain late Friday while producing thunderstorms downstate—one of which spawned a tornado around 3 p.m. in east-central Illinois near the Indiana border, 4 miles north of Casey, Ill. The twister there was photographed and appeared to occur at the front of the thunderstorm rather than beneath the southwest quadrant of the parent cumulonimbus (the cottony cloud which produces t-storms). This suggests the swirling winds may have been part of a less conventional, shallower circulation known as a “gustnado.”
A cold front, which slashed readings 30-plus degrees between Thursday afternoon and Friday evening, is northbound again. It’s to pass Chicago between 3-4 p.m. this afternoon, shifting cool ESE winds off the lake more southerly.
--By Tom Skilling, WGN-TV Chief Meteorologist

This impressive photo of a Friday afternoon (May 25) tornado comes to us from Kurt Coffey, who was scouting corn near Casey, Illinois, when the twister appeared 1/2-mile away. A tornado warning had been issued at 3:02 p.m. by the National Weather Service's Lincoln, Illinois, office on the basis of a Doppler radar indication of rotating winds. It's possible this tornado may be the latest to fall into the "gustnado" category given the fact the circulation appears to have occurred at the leading edge of the thunderstorm rather than in the more conventional rear-southwest quadrant of the storm. Gustandoes form when outflowing winds spin up a vortex at the front of a strong thunderstorm. Our thanks to Kurt Coffey as well as to Mike Toohill, a colleague of Kurt's, who called this remarkable shot to our attention.
--By Tom Skilling, WGN-TV Chief Meteorologist

The sun was out, yet the wind howled Thursday gusting to 54 m.p.h. at southwest suburban Romeoville and 50 m.p.h. at DeKalb. The powerful non-t-storm winds snapped tree limbs, which in turn downed power lines. As many as 21,000 Com Ed customers were without power for a time at the height of Thursday afternoons outages around 5 p.m. The gales fanned the flames of major fires in Harvey and Bolingbrook. Chicago’s Streets and Sanitation crews responded to 450 reports of damage to trees and traffic signals.
Thursday powerful gusts were the product of a vertical alignment (or “stacking”) of strong southerly winds through the lowest eight miles of the atmosphere. Surface winds can become especially powerful when all atmospheric momentum is channeled in a single direction. Blowing dust off freshly plowed fields the length of Illinois became airborne contributing to the hazy appearance of Thursday’s skies.
--By Tom Skilling, WGN-TV Chief Meteorologist

Powerful winds blast the area Thursday with occasional 40+ m.p.h. wind gusts, propelling Chicago area temps to the highest levels of 2007. The predicted high of 92° would make it the city’s warmest since Aug. 2 last summer and produce a temperature within striking distance of the 93° record set in 1950. It would also mark the fourth consecutive 80°+ day in a May which has tallied more 80s than any since 1987. May 2007 now ranks 20th warmest of the past 137 years. It’s been 25 years since Chicagoans have witnessed a total of 13 days with 80s this early in the season.
Highs flirted with 90° a second day Wednesday at the city’s official weather observation sites—O’Hare and Midway (both 89°). But many locations reached 90°, including Lansing, Kankakee, and Rockford. Gary was the area’s warm spot with a 91° high. Historically, Chicago’s first 90° high has occurred on or about May 28.
--By Tom Skilling, WGN-TV Chief Meteorologist

Southerly winds gusted to gale force under Wednesday's sunny skies, downing these tree limbs west of Chicago in Lee County's Franklin Grove. Anthony Parks took these photographs which clearly show you don't need thunderstorms to produce damaging winds. Wind gusts 40 mph and higher were detected by several of our WeatherBug sensors across the area. My colleague Eric Sorensen, who's Chief Meteorologist at WREX-TV in Rockford, who called Anthony Parks photos to our attention, correctly note these winds were of tropical storm strength! And, the powerful winds are likely to continue Wednesday night through Thursday.

Tom Skilling

PHOTO COURTESY: Anthony Parks

It was more like July than May Tuesday as temperatures flirted with 90°, making it 2007’s second warmest day. Afternoon highs peaked at levels 15° above normal, including an 89° high at Rockford and 88° highs at Midway Airport, Aurora, Kankakee, Lansing and Joliet. The warmth even managed to overpower cool air near Lake Michigan, making it all the way to Chicago’s lakefront. Northerly Island hit 86°. North lakeshore communities like Waukegan and Kenosha were the only ones denied the full impact of Tuesday’s warmth thanks to cool breezes off Lake Michigan.
With 12 highs of 80° or higher on the books in 2007, this year ranks among the city’s most prolific 80° producers so early in the season. Only nine of the past 37 years have had as many or more. This month’s tally of ten 80s—including Wednesday’s predicted 89° high—is the most for the May 1-23 period in two decades.
--By Tom Skilling, WGN-TV Chief Meteorologist

Meteorological Spring, 2007—now into its 11th week with just 10 days to run—adds to its temperature surplus in coming days. It’s likely to go down in the books as a warm one, despite the brief but jarring temperature downturn Sunday. Monday’s high hit 80° making it the 10th reading at that level to date this year. Only two 80s had occurred by this date a year ago. Though lingering lake breezes restricted highs Monday to the 60s from Chicago’s lakefront north to Waukegan and Kenosha, a number of observation sites west and south of Chicago registered even warmer readings—among them 87° at Rockford, 86° at Aurora, Romeoville, Kankakee and Morris.
Temperatures surge well into the 80s Tuesday and Wednesday. That would make the current warm spell the area’s longest since early September. The twelve 80s expected to be on the books by Wednesday’s close are the most so early in a warm season in the 20 years since 1987!
--By Tom Skilling, WGN-TV Chief Meteorologist

Temperatures dropped 15 degrees almost immediately as a cold front passed through the area Sunday morning. In the afternoon, the front stalled after moving well south of Interstate 80, leaving a huge 30-degree-plus temperature differential across northeast Illinois from the upper 40s along the Lake Michigan shoreline to the lower 80s to the southwest in Grundy County.
The frontal boundary so perfectly depicted in the satellite photo displayed on this page is expected to move back north as a warm front today, reversing yesterday’s cool down with a similar warm-up—by mid afternoon much of the city may well make up Sunday’s 30-degree differential with readings reaching 80° to the south and west and the mid to upper 70s north. Conditions should become more humid the next couple days as 80° warmth continues over northeast Illinois. Clouds thicken Wednesday with a good chance of thunderstorms that night ahead of a cold front.
--By Paul Dailey, WGN Weather Center Meteorologist

What a difference a day makes. After a spectacular 80º Saturday marked by brilliant sunshine and humidity levels below 20%, Chicagoans face the prospect of a very chilly Sunday as brisk NE winds sweep lake-chilled air into the city. Areas very close to Lake Michigan could experience a temperature drop of more than 30º with temperatures Sunday afternoon struggling to reach the lower 50s. The chill will moderate farther inland with readings reaching more comfortable levels in the lower and middle 70s in areas west of the Fox Valley. A few showers could accompany the cold air’s arrival Sunday morning, but any precipitation is expected to be quite light.
The chill will be short-lived with the mercury climbing well into the 80s with a few areas pushing 90º by Tuesday. In typical late spring fashion, another cold front will arrive by the end of the week with a round of potentially active showers and t-storms, followed by another temperature downturn.
--By Steve Kahn, WGN Weather Center Meteorologist

With the opening 18 days of May 2007 ranked 23rd warmest of the past 136 years, area temperatures are predicted to reach or top 80° for the ninth time in 2007 Saturday afternoon. The pace at which 80s have been occurring is running well ahead of normal. May’s 61° average temperature is 6 degrees above the same period a year ago. Yet, of the 11 meteorological spring weekends on the books, this becomes only the third to log an 80° high.
Despite the past week’s thundery rains, Chicago’s official May rain tally of 0.65” at O’Hare is only one-third of the long-term average—low enough to make this the 19th driest May here since 1871. Of nine May 1-18 periods we’ve examined with comparably limited rainfall, six of them were followed by summer seasons with below-normal rainfall.
Computer precipitation estimates suggest that the Chicago area’s potential total rainfall into the opening two days of June may range from 0.94” to 2.24”.
--By Tom Skilling, WGN-TV Chief Meteorologist

Overnight temps as low as 33-degrees in the Sugar Grove/Aurora area
Our thanks to Brad Clemmons out in Chicago's west suburban Fox Valley
area who photographed Friday morning's frost in his back yard. Frost
was reported in many areas surrounding Chicago and away from Lake
Michigan. This morning's daybreak temperatures were the coldest here in
a month! Thanks again, Brad, for sharing the photos with us!
--By Tom Skilling, WGN-TV Chief Meteorologist

Temperatures were in free fall late Thursday, predicted to bottom out in the 30s across cooler sections of the Chicago metro area early Friday—the lowest readings here since the 36° low nearly a month ago on April 17. Temps that low at such a late date are rare. Only 36 of the 8,086 sub-39° low temperatures on record at Midway Airport over the past 79 years have occurred between May 18 and the arrival of warm summer weather. That’s just 4/10ths of a percent of all low temps on the books since 1929.
Dew points become an invaluable aid in predicting low temperatures in this sort of pattern. That’s because overnight temperatures often tumble toward the dew point when skies are clear, winds are light and the air is exceptionally dry.
North Woods residents in upstate Wisconsin and Minnesota really shivered Thursday morning. Lows dropped to 23° at Land O’Lakes Wisc. and 27° at Hibbing and International Falls, Minn.
-By Tom Skilling, WGN-TV Chief Meteorologist

With the cleanup from this week’s first wave of thunderstorms only getting underway across southern suburbs into Indiana Tuesday afternoon, the last thing the Chicago area needed was a new outbreak of powerful storms. Yet, that’s exactly what happened Wednesday afternoon. A pool of unseasonably cold air aloft, combined with daytime heating caused the atmosphere to destabilize rapidly encouraging air to ascend with a vengeance. T-storms were the result. Only this time, its was the northern suburbs which bore the brunt of the storms. For an hour and a half beginning north of Rockford just after 4 p.m., bursts of strong winds gushed out of southeastbound t-storms radar-scanned up to 30,000 ft. tall. A trail of damage was soon strewn from the Illinois/Wisconsin line into McHenry County and across northern Kane and DeKalb counties east to Lake Michigan.
--By Tom Skilling, WGN-TV Chief Meteorologist

My meteorological colleague Rick DiMaio shares this revealing shot from North Lakeshore Drive of the ominous "shelf cloud" with Wednesday evening's powerful thunderstorm cluster. The storms produced damage and local 40-50 m.p.h. wind gusts over a broad area of Chicago's north and far northwest suburban area—but, interestingly, peak velocities of 25 m.p.h. at O'Hare International and 18 m.p.h. at Midway Airport. The rush of cold air out of the leading edge of a thunderstorm like Wednesday's cools air ahead of the cloud to condensation producing the rolling shelf cloud in the process.

Thanks Rick for the spectacular shot!

Tom Skilling

Photo courtesy: Rick DiMaio

An eruption of powerful afternoon t-storms Tuesday sent damaging winds, clocked at times above 60 m.p.h., blasting across sections of Chicago’s southern suburbs. They turned deadly in unincorporated Porter County, Ind. between 3 and 4 p.m., when a 75 ft. tree was blown onto a car traveling on State Road 149, crushing the vehicle and killing its driver. The outbreak marked the second time in the three weeks since another major severe weather outbreak on April 26 that storms have lambasted the south suburban corridor extending from Will County east to St. Joseph County in Indiana. Notre Dame University’s historic Basilica was damaged and several 100 year old trees were downed on campus. Storms towered to heights of 48,000 ft. and exploded to life in Tuesday’s 80°+ warmth—the eighth such reading of 2007. Rains which accompanied the storms totaled as much as 1.11” at Beecher in Will County.
--By Tom Skilling, WGN-TV Chief Meteorologist

These dramatic shots were taken this afternoon by Chuck Hagen who was driving south of I-80 near Peotone when this gust front hit spinning up a possible gustnado. The strong winds overturned an 18 wheeler just to the south and went on to produce some damage to the east in Lake and Porter counties of northwest Indiana. Our thanks to Chuck for sharing these shots with us.

Photos courtesy of Chuck Hagen of Oak Lawn

Tony Lyza provides us these photographs of damage produced a quarter mile north of Schererville, Indiana and and near Cedar Lake, Indiana and near Route 1 south of Beecher. He shot these during a storm chase and tells us:

"We noticed a concentrated column of dirt, what may have been either a weak landspout or a gustnado (it was difficult to tell given the turbulent cloud bases and copious scud). We left for the tornado-warned cell to the south of us and the damage you will see coming up. On our way back, we searched near where this occurred and found this damage. Note that the view is to the SE, and there are freshly-fallen trees lying both toward the east and, especially noticably, to the west."

Thanks Tony to you are your chase team for the great shots!

Tom Skilling
Chief Meteorologist
WGN-TV

Photo courtesy: Tony Lyza

Sun bathers were out in force on Chicago beaches Monday as temperatures soared to 2007’s highest level yet. Powerful SW winds, which gusted to 37 m.p.h., delivered the city’s earliest 90° temperature in 13 years—since 1994. On only 17 occasions since weather records began at Midway Airport in 1928 has a 90° temp arrived any earlier. The 90° high at O’Hare was the city’s first official 90° high since a 97° reading 9+ months ago on Aug. 2. Highs of 90° were also recorded at Midway Airport and Northerly Island on Chicago’s lakefront. There, southwest winds blasted across the lakeshore and out over Lake Michigan, extinguishing the chilly 50s which had hugged the lakeshore all weekend thanks to northeast winds off relatively cold lake waters. While the 90° reading at O’Hare fell just 2° shy of a 1982 record, the 92° at Rockford eclipsed the city’s 75-year previous record for the date of 91°. --By Tom Skilling, WGN-TV Chief Meteorologist

Abundant sunshine and strong southwest flow today should result in Chicago’s highest temperatures so far this year. Highs near 90° in some locations south and far west are not out of the question.
However, lightning should be visible to the northwest later tonight as a cold front approaches. By Tuesday morning, the cold front will be moving into the metro area with showers and thunderstorms occurring or imminent. As the day progresses, winds will shift to the north and temperatures will fall through the 60s. Tuesday’s half-inch or more rains may be enhanced slightly in some parts of the area Wednesday as cold air aloft generates some spotty brief showers, but that should be about it for rain here until early next week.
A huge blocking high pressure ridge aloft pattern will migrate slowly across the northern Plains the rest of the week through next weekend until finally passing to the east, allowing the next chance of rain Tuesday, May 22.
--By Paul Dailey, WGN Weather Center Meteorologist

After a chilly start this morning temperatures moderate Sunday as winds turn SE and then southerly, eventually allowing the area to evade the cooling effects of Lake Michigan. Strengthening southwest winds will then push the potentially warmest air of 2007 into northeast Illinois on Monday. The increased moisture content of the warmer air will lead to the development of showers and t-storms along an approaching cold front later Monday night/Tuesday. Highs are expected to climb into the mid to upper 80s by Monday afternoon and then fall through the 60s Tuesday as winds turn NE off Lake Michigan behind the southward-moving cold front.
Wednesday cold air aloft will sink, forcing the relatively mild 60° surface air to rise and condense into clouds and showers.
As the cool high pressure air mass drifts south and east, southerly flow will return with warming again by the end of the week.
--By Paul Dailey, WGN Weather Center Meteorologist

This weekend opens noticeably cooler than its predecessors. There hasn’t been a Saturday in four weeks—since April 14th when the high was only 49°—with cooler daytime readings.
Saturday dawns with temperatures 40 degrees lower than Thursday afternoon’s 84° high—the warmest reading of 2007 to date. It’s the biggest 2-day plunge in May since May 10-12, 2001, when readings tumbled from 81° to 38°. May has hosted some eye-catching temperature pullbacks—some even more significant than this one. Back in 1925, residents endured a 57-degree May temperature plunge—from 94° to 37° between the 23rd and 25th.
Northeast winds gusted to 35 m.p.h. at Midway Airport and to 37 m.p.h. at the Harrison-Dever Crib three miles offshore as the chill arrived. Though south suburban Kankakee reported 81° at noon, the surge of cool air sent readings there tumbling to just 54° by late evening—a 27-degree drop in less than 9 hours!
--By Tom Skilling, WGN-TV Chief Meteorologist

This fascinating Thursday dust devil 87 miles due west of downtown Chicago near Franklin Grove in Lee County, Illinois, was photographed by Anthony Parks of Franklin Grove, Illinois. Anthony tells me the dust devil, which looks like a mini-tornado and is a region of swirling wind and dust, was about 30 yards across at its base and extended at one point about 100 feet into the air. It formed over plowed ground. Temperatures had soared into the 80s across all but lakeside areas of northern Illinois, and dark-colored plowed soil heats more than the ground around it. This enhanced heating enhances thermals (columns of rising air) which form above it -- which is no doubt what ultimately contributed to the dust devil's formation. Many thanks to Anthony Parks for taking these remarkable photos, and to my colleague Eric Sorensen, Chief Meteorologist at WREX-TV Rockford, for calling Anthony's pictures to my attention.
--By Tom Skilling, WGN-TV Chief Meteorologist

Photos courtesty of Anthony Parks, Franklin Grove, Illinois

Much of the area beyond the reach of cool breezes off Lake Michigan returns to the 80s Thursday. For west suburban residents, it marks the 4th consecutive day with temperatures 80° or higher.
A fog and low cloud generating lake breeze swept several miles inland late morning Wednesday, at one point lowering lakeshore air temperatures to the mid 50s while west and south suburban locations flirted with 80°.
Except for brief, thundery showers early Wednesday, May has opened with more rain-free days than any over the past 15 years. May’s overall warmth makes the month the 21st mildest of the past 137. Mild temperatures continue into Friday with 80s away from the lake. A temperature downturn is likely as gusty NE winds take hold off a Canadian high pressure later Friday and Saturday.
Resurging warmth late Sunday sets the stage for 2007’s warmest reading yet (87°) on Monday.
--By Tom Skilling, WGN-TV Chief Meteorologist

The Chicago area came close to a serious tornado encounter last September 22—an encounter which could have proved disastrous. That's the subject of a special report we air Wednesday evening on WGN-TV's Nine O'Clock News.

The event last autumn underscores our area's vulnerability to twisters. A tornado touched down on the Loyola University Sheridan Road campus on Chicago's far north side and became the waterspout pictured here in dramatic shots provided to us by Steve Wells and Nick Dalzell, SAE fraternity brothers and Loyola students. The supercell thunderstorm which produced this waterspout actually formed well west of Chicago in Batavia, Illinois. A National Weather Service analysis shows its circulation tracked across Wheaton, I-355, the Tri-State (both during the evening rush hour) and directly over O'Hare International's terminal before producing a tornado touching down on the Loyola campus and proceeding harmlessly (though dramatically) out over the lake.

The scenario could have been much different had the touchdown occurred farther west. We explore this close call with a tornado on our report on the Nine O'Clock News tonight and talk with Chicago emergency preparedness officials on how the city has prepared for such a potential disaster and tips on what to do if a tornado threatens. We hope you'll join us.

-Tom Skilling
WGN-TV Chief Meteorologist

Photo Courtesy: Steve Wells and Nick Dalzell

Words fail one in describing pictures of the devastation inflicted last Friday evening around 9:30 p.m. Kansas time by the now infamous EF5 twister ("Enhanced Fujita Scale tornado intensity level 5 indicating 200 m.p.h.+ winds) which all but obliterated nearly every structure in Greensburg, Kansas. It was the worst single tornado to touch down in the U.S. in eight years (since the Moore, Oklahoma EF5 twister in May, 1999).

These photos were relayed to me by a colleague of mine here at WGN—Terry Bates of our engineering department—whose brother Perry is a Kansas resident who was forwarded these shots by Larry Holliday, a Morton County deputy.

The mammoth "wedge" tornado responsible for the utter devastation cut a path 1.7 miles wide and 22 miles long across the Kansas landscape. Preliminary reports in to the Storm Prediction Center put the past week's tornado count at over 170—nearly a quarter of all the U.S.tornadoes on the books to date for 2007. Dan McCarthy of the Storm Prediction Center, in a conversation I had with him several days ago, indicates this year's tornado pace is running almost twice normal.

Many thanks to Terry and Perry Bates, and Larry Holliday for these photos. They certainly underscore the scope of the Greensburg, Kansas tragedy.

--Tom Skilling

Photos courtesy: Perry Bates and Larry Holliday

Official highs of 83° and 82° Monday and Tuesday marked Chicago’s first back-to-back 80s since last September. Using history as a guide, the twin 80s arrived on schedule. Consecutive 80° highs have occurred within a day or two of May 5 over the 79 years weather observations have been taken at Midway Airport.
An unusually powerful late season coastal storm off the Southeast Coast may be investigated by Air Force Reserve Hurricane Hunters Wednesday. At present, the storm is producing 50+ m.p.h. gales and two story high seas, but it’s technically a non-tropical system, which means the temperatures aloft in its clouds remain cold and there is a discernible temperature spread across the system. The cloud formation process over warm ocean waters in storms of this type has been known to release such huge quantities of latent heat energy, that its clouds have warmed—an important step toward tropical storm or hurricane formation.
--By Tom Skilling, WGN-TV Chief Meteorologist

Flooding of an intensity not seen across the U.S. Heartland since the Great Flood of 1993, appears to be unfolding across sections of the Plains—an area hit repetitively last weekend by thundery downpours totaling as much as 10" at some locations. Nicholas Eckstein, a Northern Illinois University alum and now meteorologist at the National Weather Service Forecast Office in Aberdeen, South Dakota, has forwarded these remarkable photos of standing water in the wake of last weekend's record breaking cloudbursts. The rainfall was so extreme, 75-90% of Aberdeen area homes were flooding and a number of cars submerged up to their windows. Nicholas, in an e-mail exchange Tuesday evening, tells us:

"Our primary concerns now are the flooding rivers, especially the James River that runs north-south through South Dakota... right along the axis of heaviest rains. The river is very high right now and overflowing in most locations... and beginning to rival record flooding. Aberdeen only averages 20.22 inches/year. We already have recorded 15.55 for this year, which is 10.83 above average and 55% of our record yearly rainfall (normally by this date we've recorded only 23% of the average yearly rainfall)."

Many thanks for sharing these revealing photos with us, Nicholas and please pass along our concern to all in the Aberdeen area. We continue to monitor your situation closely.

Tom Skilling,
Chief Meteorologist
WGN-TV

PHOTO COURTESY: Nicholas Eckstein

Chicago area residents, in the midst of extraordinarily low 21% relative humidities only two days ago, awaken to a different environment Tuesday. Muggy Gulf air behind one of the most challenging early May opens in recent memory across the Plains, has reached Chicago. It raises the specter of thundery downpours here possibly accompanied by hail, especially Tuesday afternoon and night. 80° warmth—tempered only by light, localized (limited area) lake breezes expected in the absence of a well organized wind regime here through Thursday—should “mix the atmospheric pot”, heating the humid air and encouraging it to rise.
Rainfall within this air mass the past 7 days has reached historic proportions in the Plains. Epiphany, S.D. has been swamped by 10” of rain while Omaha, Neb. has logged more than 8 times its typical early May rain—recording 7.46”.

--By Tom Skilling, WGN-TV Chief Meteorologist

Dry air invaded Chicago Sunday, dropping dew points into the 20s and producing a 21 percent relative humidity level at Midway Airport—the lowest value recorded here since a 17 percent reading back on Feb. 26, 2006. The dry conditions will not last long, however, as warm and considerably more humid air is expected to surge into the area on Monday, setting the stage for several periods of showers and thunderstorms beginning Monday night and continuing into Wednesday.
Severe weather continued to rake the Plains Sunday, though activity was greatly reduced from Saturday’s battering that produced reports of 93 twisters.
It is only May, but hurricane forecasters are focusing their attention on a low pressure system off the Carolinas. Currently producing winds to nearly 50 m.p.h., the non-tropical system is expected to strengthen as it loops westward toward the Southeast coast and possibly gain some tropical characteristics.
--By Steve Kahn, WGN Weather Center Meteorologist

More than 120 twisters have ravaged portions of the Plains since Friday as a slow-moving storm system hovers over the region. Stunned residents of Greensburg in southwest Kansas were sifting through the rubble that once was their town until it was devastated by a powerful twister Friday night that killed at least nine and injured scores. More twisters are expected in the Plains Sunday as the area remains under an elevated severe weather risk.
Locally, Chicago’s recent string of cool days dominated by brisk east winds will come to an end by Monday as a wind shift into the south will send temperatures surging to summerlike levels in the 80s along with a noticeable increase in humidity. Once established, the warm spell is expected to persist through most of the week and may trigger the city’s first real need for air conditioning this season. The arrival of the warm and humid weather should also ignite a few periods of showers and thunderstorms this week.
--By Steve Kahn, WGN Weather Center Meteorologist

The easterly winds—which, by late Sunday, will have blown for five full days—have acted as an atmospheric buffer against recent downstate downpours. Even as the northbound moist air fueled rains in its trek across the southern Midwest, the precipitation has largely evaporated here thanks to dry low-level air which has arrived with the brisk easterly flow.
Thunderstorms downstate Friday led to three brief tornado touchdowns in the St. Louis area. Other storms unleashed impressive rains across southern Illinois and Indiana as well as Kentucky and Missouri. Heavier amounts Friday included 1.56” Louisville, 1.45” St. Louis, 1.01” Effingham, and 0.81” Evansville. Another 0.75” doused Poplar Bluff, Mo., where 2” had fallen on Thursday.
Saturday’s overcast and brief rains promise, in combination with east winds off the lake, to limit shoreline warming. But drying by Sunday allows unlimited sunshine to return, which should boost readings back to the 70s.
--By Tom Skilling, WGN-TV Chief Meteorologist

Jim Marocchi of Winfield shares these shots of Friday morning's sunrise over Schaumburg and Arlington Heights! Cirrostatus and some altostratus are visible. The clouds are off a storm system responsible for flooding rains over the southern Midwest -- a system likely to provide clouds and some showers here by Friday night into Saturday. Thanks for sharing these photos with us, Jim!
--By Tom Skilling, WGN-TV Chief Meteorologist

Waves of thunderstorms unleashed blinding downpours on already waterlogged southern Midwest soil Thursday. The runoff which resulted swept over roadways and forced farmers from their fields. Water over a roadway a mile east of Winona in far southern Missouri was so high that at least one motorist had to be rescued. Some of the heaviest Missouri rainfalls Thursday included 3.50” at Winona—more than a full May’s typical rainfall in Chicago—2.09” at Poplar Bluff, and 1.32” at Farmington.
Up to now, cool easterly winds have acted as a powerful buffer to the northbound moisture responsible for big rains to Chicago’s south. But, persistent southerly winds above the surface are to chip away at the dry air, slowly saturating the atmosphere. The result by Friday afternoon includes cloudier skies and growing prospects for some scattered light showers, becoming more numerous Friday night.
--By Tom Skilling, WGN-TV Chief Meteorologist

A slide toward La Nina conditions, which began with unusual speed across the equatorial Pacific in February, may impact Chicago’s summer weather. A series of computer forecasts predict a La Nina of at least moderate intensity. Equatorial Pacific Ocean temps may end up as much as 1.5 to 3° cooler than normal—signaling a well developed La Nina. Though La Nina’s global effects are generally considered less pervasive than El Ninos, in-house analyses have linked a slight tendency toward wetter than normal springs with the event. Stronger La Ninas have impacted summer weather as well. In eight of nine warm seasons since 1950 identified as having coincided with La Ninas comparable to the one predicted this summer, Chicago temps have averaged warmer than normal overall from June through August. These years have produced an average of 33 days of 90s at Midway Airport—more than the average of 24 since 1928.
--By Tom Skilling, WGN-TV Chief Meteorologist

I want to share with you these amazing photos forwarded to us by Chad Cowan, who with two chase partners, traveled first to Oklahoma then north to Kansas last week. Chad describes the encounter with the storms you see here:

"With the set up and potential of a classic tornado outbreak, myself and two chase partners left Illinois on Monday night (4/23) with the target area of north-central Oklahoma. After arriving in Enid, OK and waiting for the storms to develop, we realized that current conditions were not conducive for tornadic supercells where we were.

Looking at forecast models and visible satellite imagery, we decided to move north and intercept a line cumulus towers developing along the dry line. 90 minutes later, as we drove north on I-35 through Wichita, the first tornado warning was issued for the line of storms we targeted.

As we moved closer to the line, we chose our target storm nicknamed "tail-end Charlie" because of its relative position on the southern most edge of the line. Although the storm was not warned at the time and did not look very impressive on radar, we chose to target this it because tail-end Charlie's usually have the most tornadic potential due to the southern end being autonomous, not being influenced by other storms and having direct access to the southern flow of moisture.

The supercell was EXTREMELY photogenic. With the sun setting, we could see the updraft tower shooting up to 45,000+ ft and corkscrewing all the way down to the funnel. The entire cloud structure was spinning like a top. The tornado lifted and dropped multiple times for about twenty minutes, and at one point there were multiple vortices. Although the actual funnel never fully condensed to the ground, there was a debris cloud. As the sun set under the base, the storm became outflow dominated and lost strength."

Thanks for these eyecatching views, Chad!!

-Tom Skilling

Photos courtesy: Chad Cowan of Chicago

Stan and Jan Burns of Duluth, Minnesota share these revealing photos taken May 1 of Wisconsin wildfire smoke trapped beneath the shallow temperature inversion above Lake Superior. The Burns tell us we are looking south from Lake Superior's northern shoreline toward Wisconsin. Many thanks, Stan and Jan, for these fascinating shots!

-Tom Skilling

Photos courtesy: Stan and Jan Burns, Duluth, Minnesota

Chicagoans were finally able Tuesday to bask in summer-level warmth which had come so tantalizingly close to the city only a day before. Temperatures broke above 80° for only the third time this year reaching 83°—a reading which tied the April 22 high for warmest of 2007. Only twice since 1970 has a May 1 been any warmer.
Midway Airport’s 84° high Tuesday was the warmest temperature in seven and a half months. Not since the 85° high last Sept. 17 has a warmer reading occurred there. The mercury sailed past 80° in the city proper just after 11 a.m. Tuesday and remained there for five hours. Not until gusty NE winds arrived in the late afternoon did temps begin plunging.
Nowhere was the dramatic temp pullback more noticeable than in Gary, Ind., where readings crashed 22° in one hour.
Winds blow easterly nearly 40% of the time in May and the next three days will be no exception.

-By Tom Skilling, WGN-TV Chief Meteorologist

Beautiful shots photographed Sunday in Crown Point, Indiana by Amanda Pickett. Thanks for sharing these with us, Amanda!!

Photos courtesy: Amanda Pickett, Crown Point, Indiana