Mount Prospect EF-1 Tornado Path 8:48 PM June 21, 2011

It only took two minutes for tornado winds to cause arcing power lines, power outages, downed trees with damaged roofs and blocked streets. Subscribe to The Cardinal EMERGENCY SCENE videos …

The National Weather Service issued a TORNADO WARNING that included northwest Cook County at 7:57 p.m. Tuesday based on doppler radar observed that indicated a severe squall line was capable of producing brief rain-wrapped tornadoes.

At 8:48 p.m. a brief rain-wrapped tornado hit Mount Prospect.

Police and Firefighters respond …
The first call related to storm damage from the tornado in Mount Prospect was received about 8:49 p.m. Tuesday for a report of a utility pole on fire from the 900 block of South See-Gwun in the backyards shared with the 900 block of South Wee Go Trail. By 8:53 p.m. Mount Prospect Fire Department already had more than five calls stacked. Firefighters reported “lots of trees down by the S-curve” at 8:54 p.m. They would continue to respond to one call after another from a stacked list until about 1:09 a.m. Wednesday. At daylight firefighters had a list of hundreds of calls printed on paper to double check and investigate for the first time. Some injuries were reported, but apparently no major injuries occurred.

The National Weather Service reported Wednesday that an EF-1 tornado struck Mount Prospect at 8:48 PM and traveled approximately 2.3 miles north-northeast with estimated maximum winds reaching 90-100 miles per hour. The tornado, which lifted at 8:50 p.m., is reported to have a maximum width of 200 yards.

By calculating the time of the tornado beginning, the lift and the distance traveled, the tornado is estimated to have traveled across Mount Prospect at about 69 miles per hour.

Tornado damage observed the morning after an EF-1 tornado struck Mount Prospect near Elmhurst Road/Main Street from Golf Road to Kensington Road. Subscribe to The Cardinal EMERGENCY SCENE videos …

Weather investigators observed ground damage, conducted an aerial survey with the help of CBS 2 Chicago, and examined Radar Reflectivity Imagery from O’Hare Terminal Doppler Radar, which showed a hook shape; and Radar Velocity Imagery, which showed a “velocity couplet” — wind velocity blowing away from the radar antenna on the east side of the image and wind velocity blowing toward the radar antenna on the west side. The images are available in a report available online from the National Weather Service Chicago (See June 21st Suburban Chicago Tornadoes).

Most tornadoes rotate cyclonically (counterclockwise) in the northern hemisphere when viewed from the perspective of the upper atmosphere. A tornado path north of O’Hare with a tornado rotating counterclockwise would show wind blowing away from O’Hare on the east side of a tornado and toward O’Hare on the west side of the tornado.