By Meteorologist Tom Skilling
Chicagoans would be wise to enjoy the seasonable level of warmth and the reduced humidities predicted Tuesday into Wednesday. That's because a shot of intense heat appears a real possibility later this week.
A 97-degree high at O'Hare Friday would be that site's hottest in 5 years
Temperatures at that time could soar well into the 90s---topping 2011's list of peak readings to date and close to a five year high at O'Hare. The last time there was a reading at the official northwest side site any higher than the 97 currently predicted Friday was a 99-degree reading observed Aug. 1, 2006.
It's a level of heat which makes Tuesday and Wednesday's upper 70 to around 80-degree highs appear eminently comfortable by comparison.
Any thunderstorm development here or nearby later this week could derail such warmth by mixing cooler air to the surface in downpours. But the predicted presence of warmth aloft---a feature meteorologists refer to as a "cap"---currently appears likely to be strong enough to easily thwart the formation of downdraft-generating thunderstorms.
Not only does the predicted "cap" and resulting thunderstorm suppression argue for intensely hot temperatures Friday, so does the fact the area appears likely to sit beneath the nose of a powerful pocket of jet stream winds---a region of the atmosphere within which air sinks, warms and compresses on a broad scale.
Intensely hot dome sets new temp records Monday across the Southwest; it's the air expected to expand into the Midwest
The heat predicted to expand into the Midwest later this week broiled the southern Plains and Southwest again Monday. Temperatures topped out at 115-degrees at Phoenix, 112 Tucson--both in Arizona, 110 Wichita Falls and 108 at El Paso in Texas and 106 and 103 at Tulsa and Oklahoma City.
Crippling drought over the southern Plains and Southwest supports bone-dry single digit relative humidities from Texas west to deserts of Arizona and southern California
Soil moisture plays a critical role in just how much warming takes place above. When hot air attempts to move up and over wet soil, these soils and the plants which grow in them return moisture to the atmosphere generating clouds and cooling thunderstorm downpours in the process.
An immense arc of above normal precipitation has occurred in recent months along the north flank of the record heat and drought which has plagued a large swath of Texas and the Southwest since last fall. The wetter than normal weather from the northern Rockies east into the central and northern Plains and over a large section of the Midwest, has contributed to the slow pace of warming which has occurred here in recent weeks.
All eyes in the meteorological community will be fixed on this heat's progress in shifting toward the Midwest late this week. If thunderstorms can be suppressed as hot air makes its move on this area, other hot surges may follow.
Current indications are heat is to stream into the Chicago area Friday and linger Saturday with 90s both days---but then a "bubble" of high pressure expected to pass immediately over Chicago later this weekend sets the stage for lighter overall winds, allowing easterly lake breezes to begin blowing into area beaches for a time later Saturday into Sunday.
Las Vegas relative humidity drops to only 1 per cent in 107-degree heat Monday; Phoenix and Tucson record 100s with 4 percent mid-afternoon relative humidities
With soils baked "dry" by relentless heat, temperatures have taken off in the blazing summer sun across the Plains and the Southwest---a process which has dropped relative humidities to stunningly low levels. Las Vegas, Nevada recorded a 1 percent relative humidity Monday afternoon with an air temperature of 107-degrees and a rare (by southern Nevada standards) dew point of minus-22 degrees. Dew points reflect moisture levels in the atmosphere, and a reading at that level is rarely found outside bitter mid-winter arctic air masses which possess virtually no moisture.
Phoenix, Arizona, with an air temperature of 115-degrees Monday afternoon recorded a relative humidity of only 4 percent. Tucson's record-tying 112-degree high contributed to a paltry 4 percent relative humidity.
Computer area rainfall estimates next 2 weeks come on heels of 5th wettest June in 84 years at Midway
Rains abated early Monday and anticipated afternoon and evening thunderstorm development took place to the north in sections of Wisconsin. Monday's early showers produced the 14th day of measurable rain in June here---well over the long term average of 9 days. The June 1-27 tally of 7.29 inches at Midway Airport makes the period the site's fifth wettest in 84 years of official records there. The amount is nearly twice the long-term average of 3.29 inches.
Chicagoans would be wise to enjoy the seasonable level of warmth and the reduced humidities predicted Tuesday into Wednesday. That's because a shot of intense heat appears a real possibility later this week.
A 97-degree high at O'Hare Friday would be that site's hottest in 5 years
Temperatures at that time could soar well into the 90s---topping 2011's list of peak readings to date and close to a five year high at O'Hare. The last time there was a reading at the official northwest side site any higher than the 97 currently predicted Friday was a 99-degree reading observed Aug. 1, 2006.
It's a level of heat which makes Tuesday and Wednesday's upper 70 to around 80-degree highs appear eminently comfortable by comparison.
Any thunderstorm development here or nearby later this week could derail such warmth by mixing cooler air to the surface in downpours. But the predicted presence of warmth aloft---a feature meteorologists refer to as a "cap"---currently appears likely to be strong enough to easily thwart the formation of downdraft-generating thunderstorms.Not only does the predicted "cap" and resulting thunderstorm suppression argue for intensely hot temperatures Friday, so does the fact the area appears likely to sit beneath the nose of a powerful pocket of jet stream winds---a region of the atmosphere within which air sinks, warms and compresses on a broad scale.
Intensely hot dome sets new temp records Monday across the Southwest; it's the air expected to expand into the Midwest
The heat predicted to expand into the Midwest later this week broiled the southern Plains and Southwest again Monday. Temperatures topped out at 115-degrees at Phoenix, 112 Tucson--both in Arizona, 110 Wichita Falls and 108 at El Paso in Texas and 106 and 103 at Tulsa and Oklahoma City.
Crippling drought over the southern Plains and Southwest supports bone-dry single digit relative humidities from Texas west to deserts of Arizona and southern California
Soil moisture plays a critical role in just how much warming takes place above. When hot air attempts to move up and over wet soil, these soils and the plants which grow in them return moisture to the atmosphere generating clouds and cooling thunderstorm downpours in the process.
An immense arc of above normal precipitation has occurred in recent months along the north flank of the record heat and drought which has plagued a large swath of Texas and the Southwest since last fall. The wetter than normal weather from the northern Rockies east into the central and northern Plains and over a large section of the Midwest, has contributed to the slow pace of warming which has occurred here in recent weeks.
All eyes in the meteorological community will be fixed on this heat's progress in shifting toward the Midwest late this week. If thunderstorms can be suppressed as hot air makes its move on this area, other hot surges may follow.
Current indications are heat is to stream into the Chicago area Friday and linger Saturday with 90s both days---but then a "bubble" of high pressure expected to pass immediately over Chicago later this weekend sets the stage for lighter overall winds, allowing easterly lake breezes to begin blowing into area beaches for a time later Saturday into Sunday.
Las Vegas relative humidity drops to only 1 per cent in 107-degree heat Monday; Phoenix and Tucson record 100s with 4 percent mid-afternoon relative humidities
With soils baked "dry" by relentless heat, temperatures have taken off in the blazing summer sun across the Plains and the Southwest---a process which has dropped relative humidities to stunningly low levels. Las Vegas, Nevada recorded a 1 percent relative humidity Monday afternoon with an air temperature of 107-degrees and a rare (by southern Nevada standards) dew point of minus-22 degrees. Dew points reflect moisture levels in the atmosphere, and a reading at that level is rarely found outside bitter mid-winter arctic air masses which possess virtually no moisture.
Phoenix, Arizona, with an air temperature of 115-degrees Monday afternoon recorded a relative humidity of only 4 percent. Tucson's record-tying 112-degree high contributed to a paltry 4 percent relative humidity.
Computer area rainfall estimates next 2 weeks come on heels of 5th wettest June in 84 years at Midway
Rains abated early Monday and anticipated afternoon and evening thunderstorm development took place to the north in sections of Wisconsin. Monday's early showers produced the 14th day of measurable rain in June here---well over the long term average of 9 days. The June 1-27 tally of 7.29 inches at Midway Airport makes the period the site's fifth wettest in 84 years of official records there. The amount is nearly twice the long-term average of 3.29 inches.
