By Meteorologist Tom Skilling
Gorgeous weather, arguably the most comfortable in 12 days, greets Chicagoans Tuesday. Gone for the moment are the downright muggy, Gulf-coast level 70-degree dew points which were such an integral part of the weather scene here for well over a week. Also behind us for now are the array of thundery downpours which produced 8.75 inches of rain at O'Hare and 3.47 inches at Midway Airport during the five day period from July 20 and 24th---including Friday night's record breaking 6.86 inch deluge at O'Hare.
To be sure, the air isn't completely void of humidity. Dew points, a measure of atmospheric moisture, are predicted to run in the low to mid 60s Tuesday. That enough moisture to "feel" if you're exerting yourself in it. But in absolute terms, the air holds less than half the water it did just days ago. A column of air over Chicago would, if all the moisture was squeezed from it, yield just under an inch of water Tuesday compared to 2.20 inches which were airborne ahead of last Friday night's thundery cloudburst in Chicago.
A "bubble" of high pressure is driving Tuesday's beautiful weather. The high has drifted into town beneath clear skies which are likely to be decorated by a few puffy summertime cumulus clouds as the day proceeds.
"Ring of fire" pattern showing new signs of life to the west; storms rake the Dakotas and Montana Monday with 70 mph gusts, local 2"+ rains
The sticky, humid pattern which set off last week's lightning displays and sporadic deluges is showing signs of life again to Chicago's west. Towering thunderstorms, some 10 miles high and responsible for a rash of 60 to 70 mph gusts across sections of Montana and the Dakotas, are to flare even farther east Tuesday, erupting in sections of Iowa and Minnesota. Some clouds blowing off these storms are to make their way into Chicago's airspace Tuesday night. And rising temperatures and surging humidities Wednesday could provoke scattered storms later Wednesday and the potential for the first of several vigorous complexes, i.e., groups, of thunderstorms Wednesday night into Thursday.
Models are advertising an atmosphere saturated with 2"+ of moisture by then and a west to east jet stream along which t-storms could flare and "train", i.e., erupt over narrow corridors repetitively. It's the same atmospheric set-up which led to the area's road and basement-flooding Friday night cloudburst.
Resurgent heat/humidity could place Chicago in a new heavy or severe thunderstorm corridor later this week, possibly as early as Wednesday night
The early read on the thunderstorms expected here Wednesday night and Thursday is that the environment in which they are likely to erupt will be moisture laden and warm. Early computer model atmospheric energy and wind shear calculations put Chicago in a corridor which could support severe weather as well as thundery downpours either here or close-by. It makes it a period which will have to be monitored.
Chicago sits just a half inch from an all-time July rain record; while areas farther north and south still in need of rain
July's 9.04 inches of rain at O'Hare places the month only 0.52 inches away from July's 122 year old record of 9.56 inches recorded in 1889. A more typical July would have a rainfall tally closer to 2.64 inches by now--just a third as much as has fallen this month. Put differently, July 2011 has a precipitation tally at O'Hare nearly three and a half times normal!
Rains have been sparse both north and south of the Chicago area. July has seen just 0.33 inches of rain at Indianapolis--3.47 inches less than normal. In downstate Springfield, Illinois, the month's rainfall tally is just 0.74 inches--only 26 percent normal. The story is the same to the north. Madison, Wisconsin has recorded only 0.64 inches of July rain and Milwaukee 1.88 inches of rain--amounts 20 and 65 percent of normal respectively.
July 2011 ranks as O'Hare's warmest since observations began at the northwest side site in 1959
July's opening 26 days are averaging 79.1-degrees. That makes the month the warmest at O'Hare since weather readings were first archived at the site beginning in 1959. The 79.1-degree average ranks as the 4th warmest July 1-26's over the full term of Chicago weather records spanning 141 years and taken at 12 different sites in the city since 1871.
Gorgeous weather, arguably the most comfortable in 12 days, greets Chicagoans Tuesday. Gone for the moment are the downright muggy, Gulf-coast level 70-degree dew points which were such an integral part of the weather scene here for well over a week. Also behind us for now are the array of thundery downpours which produced 8.75 inches of rain at O'Hare and 3.47 inches at Midway Airport during the five day period from July 20 and 24th---including Friday night's record breaking 6.86 inch deluge at O'Hare.
To be sure, the air isn't completely void of humidity. Dew points, a measure of atmospheric moisture, are predicted to run in the low to mid 60s Tuesday. That enough moisture to "feel" if you're exerting yourself in it. But in absolute terms, the air holds less than half the water it did just days ago. A column of air over Chicago would, if all the moisture was squeezed from it, yield just under an inch of water Tuesday compared to 2.20 inches which were airborne ahead of last Friday night's thundery cloudburst in Chicago.
A "bubble" of high pressure is driving Tuesday's beautiful weather. The high has drifted into town beneath clear skies which are likely to be decorated by a few puffy summertime cumulus clouds as the day proceeds.
"Ring of fire" pattern showing new signs of life to the west; storms rake the Dakotas and Montana Monday with 70 mph gusts, local 2"+ rains
The sticky, humid pattern which set off last week's lightning displays and sporadic deluges is showing signs of life again to Chicago's west. Towering thunderstorms, some 10 miles high and responsible for a rash of 60 to 70 mph gusts across sections of Montana and the Dakotas, are to flare even farther east Tuesday, erupting in sections of Iowa and Minnesota. Some clouds blowing off these storms are to make their way into Chicago's airspace Tuesday night. And rising temperatures and surging humidities Wednesday could provoke scattered storms later Wednesday and the potential for the first of several vigorous complexes, i.e., groups, of thunderstorms Wednesday night into Thursday.
Models are advertising an atmosphere saturated with 2"+ of moisture by then and a west to east jet stream along which t-storms could flare and "train", i.e., erupt over narrow corridors repetitively. It's the same atmospheric set-up which led to the area's road and basement-flooding Friday night cloudburst.
Resurgent heat/humidity could place Chicago in a new heavy or severe thunderstorm corridor later this week, possibly as early as Wednesday night
The early read on the thunderstorms expected here Wednesday night and Thursday is that the environment in which they are likely to erupt will be moisture laden and warm. Early computer model atmospheric energy and wind shear calculations put Chicago in a corridor which could support severe weather as well as thundery downpours either here or close-by. It makes it a period which will have to be monitored.
Chicago sits just a half inch from an all-time July rain record; while areas farther north and south still in need of rain
July's 9.04 inches of rain at O'Hare places the month only 0.52 inches away from July's 122 year old record of 9.56 inches recorded in 1889. A more typical July would have a rainfall tally closer to 2.64 inches by now--just a third as much as has fallen this month. Put differently, July 2011 has a precipitation tally at O'Hare nearly three and a half times normal!
Rains have been sparse both north and south of the Chicago area. July has seen just 0.33 inches of rain at Indianapolis--3.47 inches less than normal. In downstate Springfield, Illinois, the month's rainfall tally is just 0.74 inches--only 26 percent normal. The story is the same to the north. Madison, Wisconsin has recorded only 0.64 inches of July rain and Milwaukee 1.88 inches of rain--amounts 20 and 65 percent of normal respectively.
July 2011 ranks as O'Hare's warmest since observations began at the northwest side site in 1959
July's opening 26 days are averaging 79.1-degrees. That makes the month the warmest at O'Hare since weather readings were first archived at the site beginning in 1959. The 79.1-degree average ranks as the 4th warmest July 1-26's over the full term of Chicago weather records spanning 141 years and taken at 12 different sites in the city since 1871.
