Storm Sirens Sound in Response to Reports of Funnel Cloud

Elmhurst sounded its storm sirens at about 3:30 a.m. Saturday morning as a severe thunderstorm was giving way to heavy rain.

The National Weather Service carried a flash flood alert, warning of continuing heavy rains, but did not issue a tornado warning. However, several western suburbs, including Downers Grove, Darien and Wheaton, sounded their sirens following reports of an unconfirmed "rotation" sighted in Bensenville, according to Twitter reports by NBC Chicago. 

Downers Grove firefighter Greg Curry also tweeted that a tornado had been spotted at Butterfield Road and Route 53.

In Downers Grove, the sirens were sounded under new guidelines adopted by the village following a powerful June 21 storm, which was later determined to include a tornado. The village had not sounded sirens in advance of that storm, despite tornado warnings issued by the National Weather Service, because no funnel cloud had been confirmed in the immediate area.

The policy was changed in early July to require the sirens to be sounded if the village received "a tornado warning issued by the National Weather Service for any area within five miles of the community or which indicates that the community is in the direct path of an oncoming tornado." For some residents on Twitter, however, Saturday's decision to activate sirens after the worst of the major thunderstorm had passed seemed all too similar to its response to the severe July 18 storm, when a loss of power delayed activation of the sirens until the storm was essentially over.

The National Weather Service in Romeoville said it had received reports of a funnel cloud, but "there was no confirmation of anything on any of those reports," said meteorologist Bill Nelson. "There was nothing on radar to confirm them."

"There were no warnings in effect at that time, either," he said. The severe thunderstorm warning issued at 12:53 a.m. had expired by 2 a.m., he said.

As for whether or not to sound sirens in response to an unconfirmed report of a funnel cloud, "it is up to the individual entity responsible for sirens in the local village or town to decide  whether to sound the alarm or not," Nelson said.

While Saturday's early storms may or may not have included a funnel cloud, they may well have been historic in terms of rainfall. Tom Skilling of the WGN Weather Center reports the unofficial tally of 6.97 inches at O'Hare International Airport would be the most rain to fall in one calendar day since 1871.