July 11 Update: About 350,000 remained without power in Chicago as of Tuesday morning. The peak outage estimate was revised upward to 868,000.
A line of severe thunderstorms brought hurricane-force winds to the Chicago area Monday morning, July 11. Although no tornadoes were reported, the extremely strong straight-line winds produced widespread power outages. At the peak, over 817,000 customers were without electricity. Commonwealth Edison reported that this was the largest outage from any storm in Chicago history.
The force of the wind moving eastward across southern Lake Michigan prompted a seiche and lakeshore flood warning as water levels oscillated rapidly by over 2 feet.
Trained spotters reported wind gusts as high as 80 mph. Wind gusts of 75 mph were measured at Midway Airport and 63 mph at O'Hare. Here are some selected reports from the National Weather Service:
PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1029 AM CDT MON JUL 11 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
0709 AM TSTM WND GST FRANKLIN GROVE 41.84N 89.30W
07/11/2011 E70.00 MPH LEE IL TRAINED SPOTTER
0715 AM TSTM WND GST ROCKFORD 42.27N 89.06W
07/11/2011 E80.00 MPH WINNEBAGO IL TRAINED SPOTTER
ESTIMATED 70 TO 80 MPH WINDS ON EAST SIDE OF ROCKFORD.
0728 AM TSTM WND GST NW DE KALB 41.93N 88.75W
07/11/2011 E70.00 MPH DE KALB IL TRAINED SPOTTER
0730 AM TSTM WND GST SYCAMORE 41.98N 88.70W
07/11/2011 E60.00 MPH DEKALB IL TRAINED SPOTTER
0735 AM TSTM WND GST ELBURN 41.89N 88.47W
07/11/2011 M65.00 MPH KANE IL TRAINED SPOTTER
MEASURED WITH ANEMOMETER. TREE BLOWN DOWN BEITH ROAD 1
MILE EAST OF RT. 47.
0740 AM TSTM WND GST CRYSTAL LAKE 42.23N 88.33W
07/11/2011 E75.00 MPH MCHENRY IL TRAINED SPOTTER
GREATER THAN 70 MPH WINDS FOR 2 TO 3 MINUTES. POWER
OUTAGES. 1 FT DIAMETER TREES AND LARGE BRANCHES DOWN.
0740 AM TSTM WND GST ROCKFORD 42.27N 89.06W
07/11/2011 E80.00 MPH WINNEBAGO IL PUBLIC
70 TO 80 MPH WINDS TRANSFORMERS DAMAGED CAUSING POWER
OUTAGE AND SEMI BLOWN ON SIDE.
0743 AM TSTM WND GST SUGAR GROVE 41.77N 88.46W
07/11/2011 M60.00 MPH KANE IL ASOS
MEASURED AT AURORA AIRPORT.
0750 AM TSTM WND GST WARRENVILLE 41.82N 88.19W
07/11/2011 E70.00 MPH DUPAGE IL TRAINED SPOTTER
60 TO 70 MPH GUSTS AND HEAVY RAIN.
0750 AM TSTM WND GST SUGAR GROVE 41.77N 88.46W
07/11/2011 M64.00 MPH KANE IL ASOS
MEASURED AT AURORA AIRPORT.
0752 AM TSTM WND GST AURORA 41.77N 88.29W
07/11/2011 E70.00 MPH KANE IL TRAINED SPOTTER
0754 AM TSTM WND GST MUNDELEIN 42.27N 88.00W
07/11/2011 M72.00 MPH LAKE IL TRAINED SPOTTER
0759 AM TSTM WND GST NAPERVILLE 41.76N 88.15W
07/11/2011 E65.00 MPH DUPAGE IL TRAINED SPOTTER
TREES BLOWN OVER.
0801 AM TSTM WND GST LIBERTYVILLE 42.28N 87.97W
07/11/2011 M70.00 MPH LAKE IL TRAINED SPOTTER
0804 AM TSTM WND GST OHARE AIRPORT 41.98N 87.90W
07/11/2011 M63.00 MPH COOK IL ASOS
0810 AM TSTM WND GST MELROSE PARK 41.90N 87.86W
07/11/2011 E60.00 MPH COOK IL TRAINED SPOTTER
0812 AM TSTM WND GST 3 SW MIDWAY AIRPORT 41.75N 87.79W
07/11/2011 M75.00 MPH COOK IL CO-OP OBSERVER
0814 AM TSTM WND GST MIDWAY AIRPORT 41.78N 87.75W
07/11/2011 M75.00 MPH COOK IL ASOS
0819 AM TSTM WND GST EVERGREEN PARK 41.72N 87.70W
07/11/2011 M72.00 MPH COOK IL TRAINED SPOTTER
0901 AM TSTM WND GST GURNEE 42.38N 87.94W
07/11/2011 E70.00 MPH LAKE IL TRAINED SPOTTER
15 INCH TREE UPROOTED.