Chicago Weather Center

Late season heat to build; temperatures in coming days to reach some of the warmest late August levels since 1953

Wed, 29 Aug 2012 02:06:58 -0600

By Meteorologist Tom Skilling

Some of the warmest late August temperatures in over a half century appear headed this way Thursday and Friday. Thursday's predicted 96-degree high would tie the record high for the date set 59 years ago in 1953 and Friday's predicted 97-degree high would fall just 2-degrees shy of the August 31 record---also set in 1953.

Hurricane Isaac is to play an important role in producing this unseasonable, late-season heat.

Air venting out the top of storms like Isaac migrates hundreds of mile from the storm and sinks. This leads to compressional warming and helps boost readings to record-breaking levels.

Records fall across sections of six states as heat builds in the Plains

Heat was evident across a good swath of the nation's heartland, Tuesday. A stifling high of 106-degrees occurred at Valentine, Nebraska. Triple digit temperatures were noted across sections of 10 states within the building dome of hot air expected to expand eastward and cover the Chicago area later this week.

Hurricane Isaac lambastes northern Gulf Coast; offshore waves top 33 feet, storm surge has hit 10+ feet and while driving downpours rake the area

While not a huge hurricane, Isaac is a slow-mover likely to continue drenching the north central Gulf Coast beyond Wednesday. The persistent and powerful winds expected to linger over the area during that period are likely to expand damage which had knocked out power to 200,000 residents by late Tuesday.

Waves towered to 33 feet off the Louisiana coast while wind gusts hit 106 mph atop an offshore oil rig on a wind sensor positioned 280 feet above the ocean surface.

Serious flooding was being reported in sections of southern Mississippi and louisiana. Rainfall in New Orleans topped 4 inches by late Tuesday evening and was expected to total 20 or more inches over sections of the Mississippi Delta region.

Tide gauges indicated Gulf water levels on the coast had topped 10 feet at some locations. Combined with horrendous wave action, the elevated water levels are likely to generate serious damage.

Landfalling Hurricane Isaac to heat, then soak Midwest

Wed, 29 Aug 2012 01:28:24 -0600

ASK TOM: What was the coldest daytime summer temp for Death Valley?

Tue, 28 Aug 2012 22:52:33 -0600

Dear Tom,
What has been the coldest recorded daytime temperature for Death Valley, Calif. during the summer?
---James Blake Robbins

Dear James,
Though noted for its scorching summer heat, with temperatures frequently in excess of 120 degrees, Death Valley occasionally experiences cooler days. Retired Chicago weatherman Paul Kubecka, an expert in Death Valley weather, provided the following information. Dating to 1911 the lowest maximum temperature ever recorded there during the June-August meteorological summer was 74 on June 6, 1925, and is the lowest of just four sub-80 summer highs in the station's history. The coolest July reading is 88 degrees on July 9, 1926, and August's lowest is 80 degrees on Aug. 19, 1983. Death Valley's all-time high temperature of 134 degrees on July 10, 1913, is now recognized as a world record.

St. Simons sunset

Tue, 28 Aug 2012 18:17:24 -0600

Thanks to Sam Yates for sending along this shot of a beautiful sunset taken on St. Simons Island off the Georgia coast.

Photo by Sam Yates

Art-deco rain gauge

Tue, 28 Aug 2012 18:13:39 -0600

Thanks to Craig and Dawn Nemitz for this picture of their colorful rain gauge which depicts a fall of nearly two inches of much needed rainfall last Sunday.

Photo by Craig and Dawn Nemitz

It looks like a funnel, but it isn't

Tue, 28 Aug 2012 18:06:26 -0600

Thanks to Bruce Wolfersberger of Shorewood for sending along this shot, which appears to be a funnel cloud but is really cloud shadows reflecting on a contrail.

Photo by Bruce Wolfersberger

Tim's Weather World: Isaac could bring drought relief

Tue, 28 Aug 2012 05:17:02 -0600

Virtually the entire state of Illinois is experiencing at least a moderate drought. More than 75% of the state is in an extreme drought and just under 8% in an exceptional drought. Remnants from Isaac could soon bring us some relief. This wouldn't be the first time a tropical storm brought much needed rain to the region during times of drought. Illinois Climatologist Jim Angel wrote recently in his blog about four such systems that brought welcome rains in 2005, another year that Illinois experienced a severe drought. Remnants of hurricanes Katrina, Rita, Dennis and tropical Storm Arlene all brought relief that year.

The "spaghetti model" plot of various model solutions (seen above) for the path of Isaac shows the majority of them sweeping the remnants across at least a portion of Illinois. The 5-day precipitation total map from the Hydrometeorological Prediction Center shows several inches of rain possible in southwestern Illinois.

It appears the earliest the remnants of Isaac could get here is Friday night. Scattered showers and thunderstorms are more likely on Saturday. Stay tuned....

http://twitter.com/WGNWeatherGuy

http://www.facebook.com

Heat ahead; August 2012, with just 4 days remaining, to end as it began--hot!

Tue, 28 Aug 2012 01:43:10 -0600

By Meteorologist Tom Skilling

   Eight of the year's 43 daytime 90-degree or higher temperatures have occurred in August and two more are on the way late this week along with a return to more humid air. The reappearance of 90s means August, on which the books close in four days Friday night at midnight, will end as it began--with 90+-degree high temperatures.

Air vented out the top of Hurricane Isaac's remnants to sink, compress and warm here, pushing 90s into the area Thursday/Friday

      Interestingly, the late week heat is to occur, in part, as air, vented out the top of Hurricane Isaac, migrates hundreds of miles ahead of the system's northbound remnants, then sinks, compresses and warms. The surge in temperatures so often observed in advance of vigorous tropical weather systems occurs through this process.

June through August meteorological summer season poised to end 3rd warmest of past 142 years

     Not only does August end in four days, so does the three-month, June through August meteorological summer season. It's poised to finish with an average temperature of 76.1-degrees--a reading well above the 71.6-degree long-term average--and behind only 1995 (76.2 degrees) and 1955 (76.5-degrees).

Stifling heat and oppressive humidities laid the atmospheric groundwork for the devastating F-5 Plainfield tornado 22 years ago

      Tuesday's predicted mid 80-degree high temperatures and moderate dew points in the 50s to low 60s are a far cry from the oppressive level of heat and humidity which greeted area residents 22 years ago this morning in 1990.
     The heat/humidity combo, in concert with a southbound cold front, the presence of an unusually strong late August jet stream and a dizzyingly sharp vertical decline in temperatures, were part of an atmospheric set-up which rendered the atmosphere explosively unstable--a perfect breeding ground for tornadic thunderstorms, which erupted during the afternoon. From those powerhouse storms, the devastating Plainfield tornado evolved.
   On the ground 15 miles and wrapped in a veil of clouds and rain, a violent, multiple-vortex tornado was able to do its deadly work--all but invisible to observers who watched the storm as it churned across the area. The tornado emanated from a southeastbound supercell which had spawned damaging straightline surface winds the length of DeKalb and in sections of west and south Kane County. But it was over the Fox River at Oswego, the thunderstorm was to go tornadic--a violent vortex which roared 15 miles across Crest Hill and Plainfield, destroying everything with which it came in contact.
     The storm, with winds at the time estimated at more than 261 mph, became the first F-5 tornado to occur in August in the U.S. and the only F-5 twister ever to strike the Chicago area. It was responsible for the deaths of 29 and injuries to 353.
   A memorial to its victims rests near the Plainfield High School all but completely destroyed by the storm.

New Orleans may become ground-zero for Hurricane Isaac; its landfall comes nearly 7 years to the day of that city's deadly, devastating rendezvous with Hurricane Katrina

     Almost 7 years to the day after infamous Hurricane Katrina laid waste to New Orleans, that city is again being threatened by a tropical cyclone--this one bearing the name "Isaac".
     Slow to strengthen much of Monday, intensification of the storm began late Monday. A suite of computer models and National Hurricane Center forecasters suggest near-100 mph sustained winds may accompany the hurricane as it makes landfall late Tuesday near New Orleans.

Storm's huge band of tropical storm strength winds to span 320 miles

   Were Isaac to be centered on Chicago at the time of its landfall late Tuesday, its 39 to 73-mph "tropical storm" force winds would reach from Pontiac, IL southwest of Chicago to near Saginaw, MI to the northeast--a span of nearly 320 miles!

Drenching rains and a damaging storm surge up to 12 ft. to accompany storm's landfall; up to 16 inches of rain forecast

    New Orleans, where a full August's worth of rain comes in at just over 5.50 inches, may see up to 16 inches of rain from Isaac.
    Even more damaging could be a combination of the system's storm surge--a dome of ocean water which sweeps onto the coastline in a hurricane's howling winds--and late Tuesday's high tide which is to occur at the time of landfall. Together these factors, along with damaging wave action, could result in as much as 6 to 12 ft of ocean water submerging vulnerable coastal areas.

Storm's remnants headed north; could bring significant rainfall to Chicago area for open of Labor Day holiday weekend

     Seventeen land falling hurricanes and tropical storms have passed within 100 miles of Chicago since 1900. They've produced varying amounts of rain and in some cases have arrived with gusty winds which have done damage.
     The expectation that "Isaac's" remnants are likely to trek north into the Midwest and the Chicago area, will be monitored closely in coming days.

Isaac New Orleans bound; Remnants likely to soak Midwest

Mon, 27 Aug 2012 22:18:26 -0600

Isaac's remnants likely to affect Chicago

Mon, 27 Aug 2012 22:14:50 -0600

By Meteorologist Steve Kahn

A strengthening Tropical Storm Isaac is expected to become a Category 2 100 mph-hurricane as it makes an expected landfall near New Orleans early Wednesday, seven years to the day after the city was hit by Hurricane Katrina. In addition to the high winds and flooding storm surge, Isaac is forecast to deluge portions of the central Gulf Coast with more than a foot of rain. Post-landfall, the storm is expected to track north up the Mississippi Valley, spreading its torrential downpours into the Midwest with the heavy rain reaching the Chicago area by the weekend.

Prior to the rain, sinking air in advance of the storm should help boost Chicago temperatures into the mid-90s Thursday and Friday. That would raise the city's total of 90-degree-plus days to 45, two shy of the record 47 logged in 1988. The heat is expected to solidify this summer's spot as the city's third hottest summer, behind 1955 and 1995 for the June-August meteorological summer period.

ASK TOM WHY: How often do we see remnants from tropical cyclones reach the Chicago area?

Mon, 27 Aug 2012 18:37:51 -0600

Dear Tom,
How often do we see remnants from tropical cyclones reach the Chicago area?
What was the most rain we ever received?
Thanks, Dan Wojtowicz

Dear Dan,
While Chicago occasionally gets rain from moisture originally associated
with tropical systems, on at least 17 occasions since 1900 remnant low
pressure systems from a hurricane or tropical storm have passed within about
100 miles of Chicago. Some like Carla's remnants in 1961 have been
accompanied by torrential rains and strong winds, while others have brought
only light showers. The city's heaviest rains from dying tropical systems
fell from September 12-14, 2008 when the remnants of Atlantic Hurricane Ike
and Pacific Tropical Storm Lowell dropped about 8.5 inches of rain producing
widespread flooding across the area.

Arc of Rainbows

Mon, 27 Aug 2012 17:51:25 -0600

Panoramic View of Rainbows Stretching Across the Sky

Thank you Randy Vinyard for the fantastic pictures.

Chesapeake Bay Shelf Cloud

Mon, 27 Aug 2012 17:37:39 -0600

Amazing Shelf Cloud Over the Chesapeake Bay

Thank you Bill Beach for the great picture.

Neil's Moon

Mon, 27 Aug 2012 17:16:41 -0600

Slightly red tinted moon rose on the night of Neil Armstrong's death.

Thanks Paul Nicol of Frankfort, Illinois

Additional 24-hour rainfall totals reported this morning from the Community Collaborative Rain Hail and Snow Network (CoCoRaHS) in northeast Illinois

Mon, 27 Aug 2012 10:50:46 -0600

Rainfall (Inches) Location County

4.53 North Riverside Cook

4.27 LaGrange Park Cook

4.06 Cicero Cook

3.98 Bridgeview Cook

3,65 Naperville DuPage

3.35 Lisle DuPage

3.24 Downers Grove DuPage

3.23 Burr Ridge DuPage

3.21 Clarendon Hills DuPage

3.21 Darien DuPage

3.04 Mendota LaSalle

3.03 Glen Ellyn DuPage

3.02 Westmont DuPage

2.90 Sugar Grove Kane

2.89 Montgomery Kendall

2.82 Braceville Grundy

2.75 Dwight Grundy

2.58 Bolingbrook DuPage

2.57 Warrenville DuPage

2.49 Chicago Ridge Cook

2.34 Plainfield Will

2.23 Channahon Will

2.23 Batavia Kane

2.17 Marseilles LaSalle

2.11 Wheaton DuPage

2.11 Chatsworth Livingston

2.08 Joliet Will

2.01 Sheldon Iroquois

1.78 Yorkville Kendall

1.63 Lombard DuPage

1.61 Morris Grundy

1.42 Bonfield Kankakee

1.42 Orland Hills Cook