Tornado Did Hit O’Hare, National Weather Service Confirms, as Twister Tally From July Derecho Climbs to Record-Breaking 27

Patty Wetli | July 22, 2024, 6:17 pm

Chicago’s Department of Streets and Sanitation has received nearly 5,000 tree emergency calls since Sunday. (Patty Wetli / WTTW News)

The twister tally from the July 15 derecho event that swept across northern Illinois has now reached a record-breaking 27 tornadoes.

The previous record was 22 tornadoes associated with a single event, as recorded by the Chicago office of the National Weather Service in its forecast area.

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Among the tornadoes most recently confirmed by the National Weather Service’s Chicago office is an EF-0 twister that blew through O’Hare International Airport, reaching peak wind gusts of 80 miles per hour.

Questions remain unanswered as to why passengers were allowed to board planes as the derecho approached, and then were left stranded on the runway as tornado warning sirens sounded and airport staff took shelter.

(National Weather Service)

The O’Hare tornado brings the number of twisters to hit Chicago to four, along with tornadoes previously confirmed in Humboldt Park/West Town, the West Loop and Chicago Lawn/West Englewood.

Trees bore the brunt of the devastating winds, but roof damage was also reported in a number of instances.

Weather service teams have been assessing more than 1,000 of these “damage points” and are still determining areas where tornadoes may have struck.

“Confirming tornadoes produced by lines of storms can be an arduous process,” the weather service said in a statement. “Rotation in squall lines can be finicky, with rapid strengthening and weakening.... Sometimes a tornado starts to develop but fails.... It’s difficult to say when this process 'officially' becomes tornadic.”

A derecho — sometimes likened to an “inland hurricane” — is defined as a long-lived, widespread swath of particularly damaging thunderstorms, covering at least 250 miles, with wind gusts of 58 miles per hour at minimum. This derecho also had embedded tornadoes.

In some areas, the weather service said, powerful straight line winds — lacking a tornado’s characteristic rotation — produced more damage than the twisters.

A separate storm on July 14 spawned six tornadoes, two of which blew through Chicago.

Here’s the latest map of confirmed tornadoes, plus areas of straight-line wind damage.

(National Weather Service)Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]