Atmospheric conditions became favorable for non-thunderstorm waterspouts during the early morning hours of September 24th, as very cold air aloft interacted with a convergence boundary along the Illinois shore of Lake Michigan. Several waterspouts were spotted during the morning hours after sunrise.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LOT wrote it up.
Atmospheric conditions became favorable for non-thunderstorm waterspouts during the early morning hours of September 24th, as very cold air aloft interacted with a convergence boundary along the Illinois shore of Lake Michigan. Several waterspouts were spotted during the morning hours after sunrise.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Chicago, IL wrote its last area forecast discussion before the first event at Sep 24, 5:25 AM CST, 48 minutes earlier.
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</html>The Milwaukee radar (KMKX), 84 km away, was scanning. The volume nearest the first event began at 12:12 UTC.
6 waterspout. Local standard time, as filed.
A waterspout was reported approximately 3 to 5 miles offshore of the Illinois Beach State Park and lasted about 20 seconds.
A waterspout was photographed from the Illinois Beach State Park and was estimated to be 3 to 5 miles offshore and lasted approximately 3 minutes.
A waterspout was reported approximately 10 miles southeast of the Great Lakes Naval Station.
A waterspout was reported 3 to 4 miles east from the shore near 47th Street.
Multiple sources confirmed a waterspout approximately 3 miles east of Chicago. The waterspout lasted about 5 minutes.
A waterspout was reported just north of Navy Pier.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Lake Michigan in 2011Every state in 2011This day in weather history
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-30. Each event’s entry at NCEI: 347569, 347272, 347273, 347276, 347277, 347278.