By Tom Skilling
The books close Saturday night on a July stunningly different than its counterpart a year ago. The month's been dramatically warmer and wetter than July 2009. Yet, perhaps surprisingly, it's also been sunnier! The Chicago area's been bathed in 21 percent more sunshine than a year ago.
There wasn't a single 90-degree reading last July -- the month's high was 86 degrees. By contrast, July 2010 has produced a dozen 90s and will finish with an average temperature around 77.8 degrees, more than 8 degrees above a year ago. The month appears on target to close among the 7 or 8 warmest and the 3rd wettest in 140 years of official Chicago weather records.
The warmth has hit Chicagoans in their pocket books: Estimates based on temperature trends suggest air conditioner usage has been nearly triple a year ago and approximately one and half times (146 percent) normal.
Meso-low to drive Chicago's Saturday winds; isolated t-storms could bubble into existence
The weather of the month's final day Saturday is to be mightily impacted by a compact low pressure -- a feature meteorologists often refer to as a "meso-low." The small disturbance is to track from southern Wisconsin Saturday morning out over Lake Michigan to just north of Benton Harbor midday and into lower Michigan by sunset.
The counterclockwise swirl of winds around the system is to produce a southwest flow as the day gets underway which is likely to shift northwest just after midday -- then run north to northeast off the lake Saturday afternoon. Winds converge within such systems. This concentrates moisture and helps foster updrafts that can carry humid air aloft where cooling produces clouds and isolated showers.
Computer models hint temperatures may decline with height at a pace modestly faster than normal. This may encourage the formation of several towering cumulus clouds tall enough to produce a mix of ice and raindrops. Such a mix separates electrical charges within the cloud and can foster lightning formation. As a result, it's possible a few isolated thunderstorms may dot the area into early afternoon.
Overall rain coverage is likely to be limited, involving as much as 20 percent of the Chicago area. So while brief downpours could affect a few locations, precipitation coverage is likely to be selective.
Deep South mired in oppressive triple-digit heat; records -- some more than half a century old -- fall
A continuation of blistering heat has prompted heat advisories for another day across the Deep South -- from the Carolinas west to sections of eastern Texas. Record-breaking temperatures occurred Friday at Jacksonville (102 degrees), Tallahassee 103, Melbourne 100, Daytona Beach 99, Vero Beach 97 and West Palm Beach 96 -- all in Florida. Other record highs included St. Simon's Island 99 and Columbus 102 -- both in Georgia.
Much of Russia in the grip of a deadly, wildfire-generating, crop-destroying heat wave--that country's hottest ever
July's weather across much of Russia has turned nightmarish. Heat has reached historic levels -- bad news in a country where air conditioning is limited. Moscow temperatures have topped 90 degrees 16 days this month, surging to triple-digits twice. Normal July highs there are around 70 degrees. The 102-degree high this past Monday was the city's hottest ever, and July is running a surplus of more than 8 degrees above normal. Crop losses have been staggering, extending across 24 million acres. Wildfires produced by the heat and the worst drought in decades have turned deadly for firefighters there in recent days.
Southwest monsoon shifts into high gear, threatens gusty t-storms across sections of 4 states
The North American Monsoon, in progress across the Southwest, threatens another day of flooding thunderstorm downpours across sections of four states -- Arizona, New Mexico, Utah and Colorado.
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