By Meteorologist Tom Skilling
Re-surging heat and humidity Wednesday threaten to set the stage for a new eruption of downpour-generating thunderstorms with strobe-like lightning and powerful wind gusts.
It was less than a week ago the area was groping with blinding rainfall and flooded streets in similar storms last Friday night and Saturday morning. Other storms had roamed the area in the days before, and did so after the record 6.96-inch cloudburst at O'Hare as well---though none of those storms rivaled what transpired in Friday night's cloudburst.
Forecasters---this one included---are hesitant to trumpet anything resembling record-breaking weather so close to an outbreak of last week's intensity. There's a reason for that. Weather history doesn't often place two such noteworthy events so close together.
Record-breaking weather events are rare by their very nature RARE and not likely to occur with great frequency.
The meteorological situation coming together Wednesday night into Thursday afternoon and/or night continues to be carefully monitored. As with last Friday night, a measurement of the atmosphere's water content suggests a situation where powerful wind gusts and driving downpours aren't out of the question over sections of the Chicago area.
Atmosphere to become comparably moist and energetic Wednesday night, boosting chances for training t-storms here or nearby; severe storms are possible too
As with last Friday night, the atmosphere's water content is predicted to top 2" Wednesday night into Friday morning---an infrequent level of moisture and one which represents an ominous signal. Moisture at such levels has be known to fuel heavy, thundery rains on more than one occasion and may again in any thunderstorms which erupt Wednesday afternoon or night.
In addition, strong west to east jet stream-level winds and impressive vertical temperature declines, on a par with those which occurred late last week, are predicted. This is critically important because falling temps with height encourage air to rise, cool and condense forming thunderstorms. The presence of strong winds aloft pushes storms along at a faster pace making them more likely to generate strong wind gusts which mix down to the surface.
That all of the conditions are in place supports the severe weather risk indicated in this area Wednesday and Thursday.
Heat and humidity re-surging; Chicago area in for the first 90+ temperature in 6 days ahead of downpour and wind-generating t-storms
Temperatures Thursday are likely to surge above 90-degrees for the first time in 5 days at Midway and 6 days at O'Hare.
Computer rain estimates in coming days average 1.69 inches--but localized totals as high as 6.90 inches hinted---but where?
Summer thunderstorms distribute their rains unevenly. That's why even our most sophisticated weather forecast models struggle in predicting how much rain is likely to fall in summer storms. It's wise to look at the full range of computer projections when trying to get a sense of potential rainfall. When you do in this case, you note that an average of 1.69 inches is being projected for Chicago.
In house models have hinted significantly more rain than that could fall, with several forecasts suggesting more than 6 inches is possible in the hardest hit locations in the next few days. Precisely where the heaviest band of rain is to set up hasn't yet been definitely nailed down. Suffice it to say, work will continue on that as the threat of new thunderstorms approaches.
Area logs the longest string of 70+ nighttime temps in 12 years; it's happened only 4 other times since 1928
For a 12th consecutive day Wednesday, Chicago's lows have registered 70-degrees or higher---the first time that's happened in 12 years and only the fourth time such a long string of warm nighttime lows has been observed at Midway Airport since 1928.
Air conditioning-usage could be up as much as 59 percent according to Summer 2011 temperature trends to date
Not only is July the warmest on record since weather observations began at O'Hare in 1959, it appears from temperature trends here that air conditioning may be running 59 percent ahead of normal July levels.
34 states broil in 90+ heat, 11 states report highs topping 100-degrees!
Stifling heat continues over the southern Plains and Texas. 34 states recorded 90+-degree highs Tuesday, 11 of them with readings which reached or exceeded 100-degrees.
Re-surging heat and humidity Wednesday threaten to set the stage for a new eruption of downpour-generating thunderstorms with strobe-like lightning and powerful wind gusts.
It was less than a week ago the area was groping with blinding rainfall and flooded streets in similar storms last Friday night and Saturday morning. Other storms had roamed the area in the days before, and did so after the record 6.96-inch cloudburst at O'Hare as well---though none of those storms rivaled what transpired in Friday night's cloudburst.
Forecasters---this one included---are hesitant to trumpet anything resembling record-breaking weather so close to an outbreak of last week's intensity. There's a reason for that. Weather history doesn't often place two such noteworthy events so close together.
Record-breaking weather events are rare by their very nature RARE and not likely to occur with great frequency.
The meteorological situation coming together Wednesday night into Thursday afternoon and/or night continues to be carefully monitored. As with last Friday night, a measurement of the atmosphere's water content suggests a situation where powerful wind gusts and driving downpours aren't out of the question over sections of the Chicago area.
Atmosphere to become comparably moist and energetic Wednesday night, boosting chances for training t-storms here or nearby; severe storms are possible too
As with last Friday night, the atmosphere's water content is predicted to top 2" Wednesday night into Friday morning---an infrequent level of moisture and one which represents an ominous signal. Moisture at such levels has be known to fuel heavy, thundery rains on more than one occasion and may again in any thunderstorms which erupt Wednesday afternoon or night.
In addition, strong west to east jet stream-level winds and impressive vertical temperature declines, on a par with those which occurred late last week, are predicted. This is critically important because falling temps with height encourage air to rise, cool and condense forming thunderstorms. The presence of strong winds aloft pushes storms along at a faster pace making them more likely to generate strong wind gusts which mix down to the surface.
That all of the conditions are in place supports the severe weather risk indicated in this area Wednesday and Thursday.
Heat and humidity re-surging; Chicago area in for the first 90+ temperature in 6 days ahead of downpour and wind-generating t-storms
Temperatures Thursday are likely to surge above 90-degrees for the first time in 5 days at Midway and 6 days at O'Hare.
Computer rain estimates in coming days average 1.69 inches--but localized totals as high as 6.90 inches hinted---but where?
Summer thunderstorms distribute their rains unevenly. That's why even our most sophisticated weather forecast models struggle in predicting how much rain is likely to fall in summer storms. It's wise to look at the full range of computer projections when trying to get a sense of potential rainfall. When you do in this case, you note that an average of 1.69 inches is being projected for Chicago.
In house models have hinted significantly more rain than that could fall, with several forecasts suggesting more than 6 inches is possible in the hardest hit locations in the next few days. Precisely where the heaviest band of rain is to set up hasn't yet been definitely nailed down. Suffice it to say, work will continue on that as the threat of new thunderstorms approaches.
Area logs the longest string of 70+ nighttime temps in 12 years; it's happened only 4 other times since 1928
For a 12th consecutive day Wednesday, Chicago's lows have registered 70-degrees or higher---the first time that's happened in 12 years and only the fourth time such a long string of warm nighttime lows has been observed at Midway Airport since 1928.
Air conditioning-usage could be up as much as 59 percent according to Summer 2011 temperature trends to date
Not only is July the warmest on record since weather observations began at O'Hare in 1959, it appears from temperature trends here that air conditioning may be running 59 percent ahead of normal July levels.
34 states broil in 90+ heat, 11 states report highs topping 100-degrees!
Stifling heat continues over the southern Plains and Texas. 34 states recorded 90+-degree highs Tuesday, 11 of them with readings which reached or exceeded 100-degrees.
