T-storms, which went on to produce flooding 1”+ downpours, hail and 70 m.p.h. wind gusts, erupted rapidly Wednesday evening. Lightning data tells the story. The evening’s fast-evolving storms began as towering cumulus clouds with radar-scanned tops near 39,000 ft. around 7 p.m., then mushroomed to a height of 60,000 ft.—apparently energized in part by heat generated by the city and converging winds near the lake. Lightning discharges grew exponentially—exploding from just 54 cloud to ground strokes in ten minutes around 7 p.m. to nearly 3,500 by 9 p.m.
Rainfall grew heavier as the storms swept across the city’s South Side totaling 1.14” in under an hour near the 5000 block of South Archer. Local 1.50”+ totals innundated NW Indiana where hail and powerful winds prompted t-storm warnings. A radar-detected tornadic circulation in Porter County led to a tornado warning while a 69 m.p.h. straight line gust was clocked at Gary.
--By Tom Skilling, WGN-TV Chief Meteorologist
WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.
