By Meteorologist Tom Skilling
Area meteorologists will be keeping a close eye on weather radars Saturday. The atmospheric set-up predicted to evolve has been known to trigger eruptions of gusty thunderstorms capable of downpours. The process will be selective, affecting some areas and not others--and it could begin as early as late Saturday morning and/or Saturday afternoon, with rain-free periods interspersed.
What's happening to concerned forecasters is the increasing rate which which temperatures are predicted to drop with height. The atmosphere is likely to undergo what meteorologist refer to as "de-stabilization". Simply put, temperatures aloft are cooling while daytime heating is warming ground-level temperatures which will peak near 80-degrees. The increase in the rate temperatures fall with height encourages warm, humid ground level air to become buoyant and rise. The cooling which results as the humid air ascends into the atmosphere encourages thunderstorms to "bubble" up, much as happened over northwest and north-central Illinois as well as in southern Wisconsin late Friday.
Friday afternoon's storms prompted weather warnings--including a tornado warning; blinding downpours and 60+ mph gusts roar across Freeport to the west of Rockford
It didn't take long for a series of thunderstorms to come to life over northwest Illinois Friday afternoon. These storms' cloud towers reached heights of 42,000 feet and produced severe weather. Blinding downpours cut visibilities to near zero for a time at Stephenson County's German Valley, where they produced flooding. Winds gusts at Freeport, to the west of Rockford, topped out at 61 mph as 0.84 inches of rain fell.
A rotating wall cloud was spotted near Esmond, Illinois and a Doppler-detected circulation prompted the issuance of a tornado warning for a time covering a section of Ogle County. The powerful storms also downed tree limbs in Stillman Valley.
To the north in Wisconsin, still another cluster of storms produced winds which flipped a boat and downed trees near Lake Mills while power lines were downed in Theresa.
A funnel cloud was reported at the Beltline and Gammon Road just west of Madison, Wisconsin by a Sheriff's Deputy. Other funnel reports came in from Clyman and 3 miles west of Jackson.
Storm clusters Saturday threaten to produce rainfalls ranging from 0.29 to 2.75-inches
Summer rainfall is notorious for its variability and uneven distribution. Thunderstorms are capable of producing a deluge at one location, while all but by-passing areas nearby. This weekend's rain situation is to be similarly varied, ranging from as little as 0.28 inches at some areas to as much as 2.75 inches in others.
Chicago's wet Summer 2011 the wettest in 54 years and 2nd wettest of the past 140
The new rains are to fall in the midst of the Chicago area's wettest meteorological summer (the period which began June 1) in 54 years. A total of 16.53 inches has occurred to date which makes this the second wettest summer to date since the official observational record began here in 1871. That amount is nearly twice the 140 year average to date of 8.62 inches.
Windy, full-fetch north/northeast flow Sunday to produce 3 to 4 ft. Lake Michigan swells
On the windy backside of this weekend's developing summer storm system, steady north to northeast winds averaging 20 to 25 mph are predicted Sunday. The flow is to travel the length of Lake Michigan over waters with an average surface temperature of 72-degrees before arriving in Chicago. The transfer of energy from those winds to Lake Michigan's water is to build occasionally white-capped swells 3 to 4 feet high Sunday.
Heat's back full force after brief break in Oklahoma/Texas; widespread 100s prevail
Thunderstorm outflows brought Oklahomans a day of heat relief Thursday. But readings bounced back with a vengeance Friday. Afternoon highs reached 101-degrees at Tinker Air Force Base in Oklahoma City and 99-degrees at the city's Will Rogers International Airport. Heat also raged in Texas where the Dallas/Fort Worth area recorded temperatures back in triple digits after a brief retreat into the 90s Thursday.
Waco, Texas, where the string of 100+-degree highs reached 61 Friday, is just two days from its all time record of 63 consecutive days set over three decades ago in 1980.
Three-day Japanese heat wave features mid 90s and heat indices 100+; air conditioning a challenge with many nuclear power plants offline
A summer heat waves grips Japan as well. Temperatures surged over 90-degrees for a third consecutive day in a number of locations, including Tokyo. Oppressive low and mid 70-degree dew points sent heat indices to triple digits. Residents are being encouraged to limit air conditioner use since two-thirds of Japan's nuclear power plans are off-line in the wake of the devastating tsunami.
Area meteorologists will be keeping a close eye on weather radars Saturday. The atmospheric set-up predicted to evolve has been known to trigger eruptions of gusty thunderstorms capable of downpours. The process will be selective, affecting some areas and not others--and it could begin as early as late Saturday morning and/or Saturday afternoon, with rain-free periods interspersed.
What's happening to concerned forecasters is the increasing rate which which temperatures are predicted to drop with height. The atmosphere is likely to undergo what meteorologist refer to as "de-stabilization". Simply put, temperatures aloft are cooling while daytime heating is warming ground-level temperatures which will peak near 80-degrees. The increase in the rate temperatures fall with height encourages warm, humid ground level air to become buoyant and rise. The cooling which results as the humid air ascends into the atmosphere encourages thunderstorms to "bubble" up, much as happened over northwest and north-central Illinois as well as in southern Wisconsin late Friday.
Friday afternoon's storms prompted weather warnings--including a tornado warning; blinding downpours and 60+ mph gusts roar across Freeport to the west of Rockford
It didn't take long for a series of thunderstorms to come to life over northwest Illinois Friday afternoon. These storms' cloud towers reached heights of 42,000 feet and produced severe weather. Blinding downpours cut visibilities to near zero for a time at Stephenson County's German Valley, where they produced flooding. Winds gusts at Freeport, to the west of Rockford, topped out at 61 mph as 0.84 inches of rain fell.
A rotating wall cloud was spotted near Esmond, Illinois and a Doppler-detected circulation prompted the issuance of a tornado warning for a time covering a section of Ogle County. The powerful storms also downed tree limbs in Stillman Valley.
To the north in Wisconsin, still another cluster of storms produced winds which flipped a boat and downed trees near Lake Mills while power lines were downed in Theresa.
A funnel cloud was reported at the Beltline and Gammon Road just west of Madison, Wisconsin by a Sheriff's Deputy. Other funnel reports came in from Clyman and 3 miles west of Jackson.
Storm clusters Saturday threaten to produce rainfalls ranging from 0.29 to 2.75-inches
Summer rainfall is notorious for its variability and uneven distribution. Thunderstorms are capable of producing a deluge at one location, while all but by-passing areas nearby. This weekend's rain situation is to be similarly varied, ranging from as little as 0.28 inches at some areas to as much as 2.75 inches in others.
Chicago's wet Summer 2011 the wettest in 54 years and 2nd wettest of the past 140
The new rains are to fall in the midst of the Chicago area's wettest meteorological summer (the period which began June 1) in 54 years. A total of 16.53 inches has occurred to date which makes this the second wettest summer to date since the official observational record began here in 1871. That amount is nearly twice the 140 year average to date of 8.62 inches.
Windy, full-fetch north/northeast flow Sunday to produce 3 to 4 ft. Lake Michigan swells
On the windy backside of this weekend's developing summer storm system, steady north to northeast winds averaging 20 to 25 mph are predicted Sunday. The flow is to travel the length of Lake Michigan over waters with an average surface temperature of 72-degrees before arriving in Chicago. The transfer of energy from those winds to Lake Michigan's water is to build occasionally white-capped swells 3 to 4 feet high Sunday.
Heat's back full force after brief break in Oklahoma/Texas; widespread 100s prevail
Thunderstorm outflows brought Oklahomans a day of heat relief Thursday. But readings bounced back with a vengeance Friday. Afternoon highs reached 101-degrees at Tinker Air Force Base in Oklahoma City and 99-degrees at the city's Will Rogers International Airport. Heat also raged in Texas where the Dallas/Fort Worth area recorded temperatures back in triple digits after a brief retreat into the 90s Thursday.
Waco, Texas, where the string of 100+-degree highs reached 61 Friday, is just two days from its all time record of 63 consecutive days set over three decades ago in 1980.
Three-day Japanese heat wave features mid 90s and heat indices 100+; air conditioning a challenge with many nuclear power plants offline
A summer heat waves grips Japan as well. Temperatures surged over 90-degrees for a third consecutive day in a number of locations, including Tokyo. Oppressive low and mid 70-degree dew points sent heat indices to triple digits. Residents are being encouraged to limit air conditioner use since two-thirds of Japan's nuclear power plans are off-line in the wake of the devastating tsunami.
