National Weather Service United States Department of Commerce

During the morning hours of July 11, 2011, a line of severe thunderstorms moved very quickly across northern Illinois and southern Lake Michigan, producing widespread wind damage.  In addition, the strong thunderstorm winds with this system generated a classic seiche event on the lake.  A seiche is a situation where lake water ahead of the storms is piled up along the downstream shore (in this case Indiana and Michigan) and then sloshes back and forth across the lake for several hours.  The danger from a seiche comes from rapidly rising and falling lake levels, which can damage watercraft along the shoreline, sweep people off piers and breakwaters, and pull swimmers far away from shore.

The storms responsible for this event developed late Sunday into early Monday across Nebraska and western Iowa.  Overnight they produced extensive wind damage across much of Iowa.  By 6:00 AM CDT as they moved into Illinois, a very moist unstable airmass (MLCAPE of 2000-4000 J/Kg) with considerable deep layer wind shear (40-50 kts) was in place ahead of the storms.  The Craven/Brooks Significant Severe Parameter, which represents the contribution from both MLCAPE and deep layer shear, was showing values as high as 60,000 m3/s3 (while normally values around 20,000 are considered sufficient for significant severe storms).

 

 11z Craven Brooks SigSvr
2011 July 11 -- 11Z Craven Brooks SigSvr Parameter

 

While the wind shear was sufficient to support organized severe storms, the westerly unidirectional nature of the winds was more conducive to the development of strong straight line wind damage versus tornadoes.  Despite the lack of directional shear, or actually because of it, the strong mid and upper-level winds were able to mix down to the surface and produce a wide swath of 60-80 mph measurements -- plus the associated damage.

This thunderstorm complex fit the description of a bow echo "derecho" which is a widespread, long-lived windstorm that is associated with a band of rapidly moving showers or thunderstorms.  The term bow echo refers to the arched, bow-like structure of the thunderstorm complex seen in the radar reflectivity data below. The same thunderstorm complex that produced widespread wind damage in the Central Plains and Midwest actually was able to persist all the way to nearly the Delmarva Peninsula in the Mid Atlantic, producing a swath of nearly continuous swath of wind damage along its path.

For more information on derechos, please refer to the Storm Prediction Center web page, About Derechos. Following the derecho categories on the SPC page, yesterday's system can be classified as a "progressive derecho."

 

13z radar and 850-300 mean wind

2011 July 11 -- 13Z Mean wind from 850-300mb

 

path of derecho from Nebraska to the East Coast
Complete path of the derecho from Nebraska to the East Coast on 10-11 July 2011

 

The effects of the seiche with this system were most readily visible from the water level measurements at the Calumet Harbor data collection platform.  The following image shows the weather conditions prior to, during, and after the passage of the line of thunderstorms.  The top graph shows water levels starting to fluctuate considerably soon after the line passed, eventually with over 2 feet of difference from peak to trough.

Calumet Harbor weather obs for 2011 July 11

 

Finally, here is a summary of the local area severe weather reports received from these storms (thru 3 PM CDT on July 11):

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
201 PM CDT TUE JUL 12 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0645 AM     TSTM WND DMG     2 NE NELSON             41.82N 89.58W
07/11/2011                   LEE                IL   EMERGENCY MNGR

            CORN FLATTENED NEAR HARMON AND ROCK ISLAND RD.

0700 AM     TSTM WND GST     LOVES PARK              42.34N 89.01W
07/11/2011  E70.00 MPH       WINNEBAGO          IL   TRAINED SPOTTER

            SEMI OVERTURNED. WINDS SUSTAINED FOR SEVERAL MINUTES.

0700 AM     HEAVY RAIN       2 ENE ROCKFORD          42.28N 89.03W
07/11/2011  M0.75 INCH       WINNEBAGO          IL   911 CALL CENTER

0700 AM     TSTM WND GST     WINNEBAGO               42.27N 89.24W
07/11/2011  E60.00 MPH       WINNEBAGO          IL   BROADCAST MEDIA

            ESTIMATED WIND GUST OUTSIDE WREX STUDIO.

0700 AM     HEAVY RAIN       1 ENE ROCKFORD          42.28N 89.04W
07/11/2011  E0.75 INCH       WINNEBAGO          IL   COCORAHS

            STORM TOTAL

0705 AM     TSTM WND GST     ROCKFORD                42.27N 89.06W
07/11/2011  M55.00 MPH       WINNEBAGO          IL   AMATEUR RADIO

            MEASURED AT 6TH AND BROADWAY.

0705 AM     TSTM WND GST     ROCKFORD                42.27N 89.06W
07/11/2011  M50.00 MPH       WINNEBAGO          IL   AMATEUR RADIO

            BYPASS 20 AND 11TH STREET.

0709 AM     TSTM WND GST     FRANKLIN GROVE          41.84N 89.30W
07/11/2011  E70.00 MPH       LEE                IL   TRAINED SPOTTER

            12 INCH DIAMETER TREES DOWN.

0710 AM     TSTM WND DMG     7 SE BELVIDERE          42.18N 88.75W
07/11/2011                   BOONE              IL   BROADCAST MEDIA

            POWER LINES DOWN BLOCKING EASTBOUND LANES OF INTERSTATE
            90 AT COUNTY LINE ROAD ON BOONE AND MCHENRY COUNTY LINE.


0710 AM     TSTM WND DMG     CRESTON                 41.93N 88.97W
07/11/2011                   OGLE               IL   TRAINED SPOTTER

            2 LARGE TREES BLOWN DOWN - 3 TELEPHONE POLES SEVERELY
            LEANING - CORN IN THE AREA FLATTENED. HALF WAY BETWEEN
            CRESTON AND MALTA, N SIDE OF IL-38, METAL BARN BLOWN
            OVER.

0710 AM     TSTM WND DMG     5 SW POLO               41.93N 89.65W
07/11/2011                   OGLE               IL   911 CALL CENTER

            CORN FIELDS LAYING FLAT AND BRANCHES 6 INCHES IN DIAMETER
            DOWN ALONG WITH POWER LINES.

0715 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.

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.

0715 AM     TSTM WND DMG     2 SW COMPTON            41.67N 89.11W
07/11/2011                   LEE                IL   EMERGENCY MNGR

            ROUNT 251 BLOCKED BY DOWNED POWER LINES NEAR SPURR RD.

0715 AM     TSTM WND DMG     2 SW COMPTON            41.67N 89.11W
07/11/2011                   LEE                IL   EMERGENCY MNGR

            RT 251 BLOCKED BY DOWN POWER LINES NEAR SPURR RD.

0717 AM     TSTM WND DMG     POPLAR GROVE            42.37N 88.82W
07/11/2011                   BOONE              IL   BROADCAST MEDIA

            OVER 30 LARGE TREES DOWN. RELAYED BY WREX.

0717 AM     TSTM WND DMG     POPLAR GROVE            42.37N 88.82W
07/11/2011                   BOONE              IL   BROADCAST MEDIA

            MULTIPLE REPORTS OF TREES DOWN IN CANDLEWICK LAKE.
            RELAYED BY WREX.

0720 AM     TSTM WND DMG     DE KALB                 41.93N 88.75W
07/11/2011                   DE KALB            IL   EMERGENCY MNGR

            TREES SNAPPED OFF AT THE BASE AT ANNIE GLIDDEN RD SOUTH

            OF RT 38. CORN ALSO FLATTENED NORTH AND SOUTH OF DE KALB.

0720 AM     TSTM WND DMG     POPLAR GROVE            42.37N 88.82W
07/11/2011                   BOONE              IL   TRAINED SPOTTER

            ROOF BLOWN OFF OF HOUSE. GARAGE ALSO DESTROYED.

0726 AM     TSTM WND GST     10 W ROCKFORD           42.27N 89.26W
07/11/2011  E55.00 MPH       WINNEBAGO          IL   TRAINED SPOTTER

            SUSTAINED WINDS AT 40 TO 45 MPH. FREQUENT CG LIGHTNING.
            DITCHES STARTING TO FILL WITH WATER.

0728 AM     TSTM WND GST     6 NNE ROCKFORD          42.35N 89.02W
07/11/2011  E60.00 MPH       WINNEBAGO          IL   TRAINED SPOTTER

            SUSTAINED WIND AT 40 TO 45 MPH. POWER OUTAGES REPORTED.

0728 AM     TSTM WND GST     NW DE KALB              41.93N 88.75W
07/11/2011  E70.00 MPH       DE KALB            IL   TRAINED SPOTTER

            TREES SNAPPING.

0730 AM     TSTM WND DMG     HARVARD                 42.42N 88.62W
07/11/2011                   MCHENRY            IL   TRAINED SPOTTER

            NUMEROUS TREES AND POWER LINES DOWN. ONE TREE FELL ON A
            HOUSE.

0730 AM     TSTM WND DMG     ROCKFORD                42.27N 89.06W
07/11/2011                   WINNEBAGO          IL   EMERGENCY MNGR

            LARGE TREE DOWN THAT TOOK DOWN SOME POWER LINES. STATE ST
            CLOSED FROM 9TH TO DIVISION.

0730 AM     TSTM WND DMG     HARVARD                 42.42N 88.62W
07/11/2011                   MCHENRY            IL   TRAINED SPOTTER

            DELAYED REPORT. E60 MPH. NUMEROUS 12 INCH DIAMETER TREES
            DOWN. TREES WERE SNAPPED OFF CLEAN APPROXIMATELY 30 FEET
            HIGH.

0730 AM     TSTM WND GST     SYCAMORE                41.98N 88.70W
07/11/2011  E60.00 MPH       DEKALB             IL   TRAINED SPOTTER

0735 AM     TSTM WND DMG     LAKE IN THE HILLS       42.19N 88.32W
07/11/2011                   MCHENRY            IL   PUBLIC

            IN THE MEADOWBROOK NEIGHBORHOOD THERE ARE NUMEROUS HOUSES
            WITH THE SIDING RIPPED OFF. MULTIPLE TREES ARE UPROOTED
            OR SNAPPED AT THE BASE. ONE HOUSE ON WATERFORD LANE HAD
            THE CHIMNEY BLOWN OFF.

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.

0735 AM     TSTM WND GST     SUGAR GROVE             41.77N 88.46W
07/11/2011  M60.00 MPH       KANE               IL   ASOS

            MEASURED AT AURORA AIRPORT.

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.

0747 AM     TSTM WND GST     CAROL STREAM            41.92N 88.13W
07/11/2011  E60.00 MPH       DUPAGE             IL   PUBLIC

            TRANSFORMER DAMAGED WITH POWER OUTAGE

0748 AM     TSTM WND DMG     YORKVILLE               41.64N 88.45W
07/11/2011                   KENDALL            IL   PUBLIC

            4 TO 5 INCH DIAMETER TREE BLOWN OVER. ESTIMATED WINDS OF
            55 MPH.

0750 AM     TSTM WND GST     WARRENVILLE             41.82N 88.19W
07/11/2011  E60.00 MPH       DUPAGE             IL   TRAINED SPOTTER

            SUSTAINED 40 TO 50 MPH WINDS.

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 DMG     ARLINGTON HEIGHTS       42.09N 87.98W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            NEAR HINTZ RD AND WINDSOR THERE ARE FENCES BLOWN DOWN AND
            AN 8 IN DIAMETER TREE SNAPPED.

0750 AM     TSTM WND DMG     WOODSTOCK               42.31N 88.44W
07/11/2011                   MCHENRY            IL   PUBLIC

            TREES DOWN WITH POWER OUTAGES.

0750 AM     TSTM WND GST     SUGAR GROVE             41.77N 88.46W
07/11/2011  M64.00 MPH       KANE               IL   ASOS

            MEASURED AT AURORA AIRPORT.

0750 AM     TSTM WND GST     N HOFFMAN ESTATES       42.06N 88.14W
07/11/2011  E60.00 MPH       COOK               IL   TRAINED SPOTTER

            INTERMITTANT POWER FAILURES.

0750 AM     TSTM WND DMG     ARLINGTON HEIGHTS       42.09N 87.98W
07/11/2011                   COOK               IL   PUBLIC

            AT THE RACE TRACK 4 TO 6 INCH BRANCHES DOWN. NUMEROUS
            TREES AND WIRES DOWN. WINDS ESTIMATED TO 70 MPH.

0750 AM     TSTM WND DMG     FOX LAKE                42.42N 88.18W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            NUMEROUS TREE LIMBS UP TO 8 INCHES IN DIAMETER DOWN.

0751 AM     TSTM WND GST     ARLINGTON HEIGHTS       42.09N 87.98W
07/11/2011  E60.00 MPH       COOK               IL   TRAINED SPOTTER

            WINDOW BLOWN OUT OF A HOUSE. NUMEROUS TREE BRANCHES DOWN.


0751 AM     TSTM WND DMG     ELGIN                   42.04N 88.29W
07/11/2011                   KANE               IL   TRAINED SPOTTER

            3 TO 4 INCH DIAMETER TREE LIMBS SNAPPED.

0752 AM     TSTM WND GST     LIBERTYVILLE            42.28N 87.97W
07/11/2011  M60.00 MPH       LAKE               IL   TRAINED SPOTTER

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

            LOTS OF LIMBS UP TO 4 INCHES IN DIAMETER DOWN. SOME LARGE
            TREES SNAPPED BLOCKING ROADS.

0754 AM     TSTM WND GST     OSWEGO                  41.70N 88.33W
07/11/2011  M60.00 MPH       KENDALL            IL   TRAINED SPOTTER

0755 AM     TSTM WND DMG     NAPERVILLE              41.76N 88.15W
07/11/2011                   DUPAGE             IL   BROADCAST MEDIA

            LARGE TREES DOWN IN PARTS OF NAPERVILLE. RELAYED BY FOX
            CHICAGO.

0755 AM     NON-TSTM WND GST NAPERVILLE              41.76N 88.15W
07/11/2011  E65.00 MPH       DUPAGE             IL   911 CALL CENTER

            TREE LIMBS DOWN.

0755 AM     TSTM WND DMG     WEST DUNDEE             42.10N 88.29W
07/11/2011                   KANE               IL   PUBLIC

            LARGE TREE LIMBS DOWN.

0755 AM     TSTM WND DMG     NAPERVILLE              41.76N 88.15W
07/11/2011                   DUPAGE             IL   TRAINED SPOTTER

            TRAFFIC LIGHT DOWN AT NAPERVILLE RD.

0755 AM     TSTM WND GST     NAPERVILLE              41.76N 88.15W
07/11/2011  E65.00 MPH       DUPAGE             IL   TRAINED SPOTTER

            TREES BLOWN OVER.

0756 AM     TSTM WND DMG     PALATINE                42.11N 88.04W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            12 INCH TREE FELL ON A HOUSE NEAR THE INTERSECTION OF
            WINDSER AND PALITINE RD. AN 18 INCH TREE WAS ALSO
            UPROOTED NEARBY. TIME ESTIMATED BASED ON RADAR.

0758 AM     TSTM WND GST     WINFIELD                41.87N 88.15W
07/11/2011  E60.00 MPH       DUPAGE             IL   TRAINED SPOTTER

0759 AM     TSTM WND GST     AURORA                  41.77N 88.29W
07/11/2011  E60.00 MPH       KANE               IL   TRAINED SPOTTER

0800 AM     TSTM WND GST     CREST HILL              41.57N 88.11W
07/11/2011  E60.00 MPH       WILL               IL   TRAINED SPOTTER

            DELAYED REPORT. SHED WALLS BLOWN IN AND SEVERAL LARGE
            BRANCHES DOWN.

0800 AM     TSTM WND DMG     EVANSTON                42.05N 87.69W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            24 INCH DIAMETER TREE DOWN AT THE INTERSECTION OF OAKTON
            AND WESLEY. OTHER TREES DOWN AS WELL.

0800 AM     TSTM WND DMG     3 S LIBERTYVILLE        42.24N 87.97W
07/11/2011                   LAKE               IL   PUBLIC

            TELEPHONE LINES DOWN ALONG WITH LARGE TREES IN PRAIRIE
            VIEW. A ROOF IS ALSO REPORTED TO BE BLOWN OFF.

0800 AM     TSTM WND DMG     OAK PARK                41.89N 87.79W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            1 FOOT DIAMETER BRANCH DOWNED WITH NUMEROUS SMALLER
            BRANCHES DOWN. HARVARD ST BETWEEN EAST AND CLARENCE.

0801 AM     TSTM WND GST     LIBERTYVILLE            42.28N 87.97W
07/11/2011  M70.00 MPH       LAKE               IL   TRAINED SPOTTER

0801 AM     TSTM WND GST     GURNEE                  42.38N 87.94W
07/11/2011  E70.00 MPH       LAKE               IL   TRAINED SPOTTER

            15 INCH TREE UPROOTED.

0802 AM     TSTM WND GST     DOWNERS GROVE           41.80N 88.02W
07/11/2011  E54.00 MPH       DUPAGE             IL   PUBLIC

0802 AM     TSTM WND DMG     DOWNERS GROVE           41.80N 88.02W
07/11/2011                   DUPAGE             IL   PUBLIC

            18 TO 24 INCH TREE BRANCHES DOWN.

0804 AM     TSTM WND GST     AURORA                  41.77N 88.29W
07/11/2011  E50.00 MPH       KANE               IL   TRAINED SPOTTER

            MANY LARGE BRANCHES DOWN.

0804 AM     TSTM WND GST     OHARE AIRPORT           41.98N 87.90W
07/11/2011  M63.00 MPH       COOK               IL   ASOS

0805 AM     TSTM WND DMG     LISLE                   41.79N 88.09W
07/11/2011                   DUPAGE             IL   TRAINED SPOTTER

            LARGE TREE BRANCHES DOWN.

0805 AM     TSTM WND DMG     GLEN ELLYN              41.87N 88.06W
07/11/2011                   DUPAGE             IL   TRAINED SPOTTER

            POWER OUTAGES

0805 AM     TSTM WND DMG     DOWNERS GROVE           41.80N 88.02W
07/11/2011                   DUPAGE             IL   AMATEUR RADIO

            POWER LINES DOWN ALONG WITH NUMEROUS TREE BRANCHES. 63RD
            ST IS BLOCKED FROM FAIR VIEW TO BELMONS

0806 AM     TSTM WND DMG     SUMMIT                  41.78N 87.82W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            5 TO 6 DIAMETER LIMBS DOWN ALONG 62ND ST WITH A 20 INCH
            DIAMETER TREE SPLIT VERTICALLY DOWN THE MIDDLE.

0806 AM     TSTM WND DMG     LONG GROVE              42.20N 88.00W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            2 FOOT DIAMETER TREES SNAPPED OFF AND UTILITY POLES DOWN
            AT THE INTERSECTION OF CHECKER AND SCHAEFER IN LONG
            GROVE.

0807 AM     TSTM WND DMG     ROGERS PARK             42.01N 87.67W
07/11/2011                   COOK               IL   BROADCAST MEDIA

            AT LEAST SIX LARGE TREES BLOWN DOWN IN LOYOLA PARK
            SECTION OF ROGERS PARK NEAR THE LAKEFRONT. ESTIMATED 18
            TO 24 INCH DIAMETER TREES. AT LEAST 65 MPH WIND GUSTS
            ESTIMATED.

0807 AM     TSTM WND DMG     LINDENHURST             42.42N 88.03W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            UTILITY POLES SNAPPED OFF AND 6 TO 8 FOOT LONG AND 2 TO 4
            INCHES IN DIAMETER.

0808 AM     TSTM WND DMG     MUNDELEIN               42.27N 88.00W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            2 TO 4 INCH DIAMETER LIMBS DOWN AT THE INTERSECTION OF RT
            83 AND RT 45.

0809 AM     TSTM WND GST     PLAINFIELD              41.62N 88.20W
07/11/2011  E65.00 MPH       WILL               IL   TRAINED SPOTTER

            AT RT 59 AND CATON RD

0810 AM     TSTM WND GST     MELROSE PARK            41.90N 87.86W
07/11/2011  E60.00 MPH       COOK               IL   TRAINED SPOTTER

0810 AM     TSTM WND DMG     WADSWORTH               42.44N 87.92W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            15 FOOT LONG BRANCHES DOWN ABOUT 4 TO 6 INCHES IN
            DIAMETER NEAR WADSWORTH RD AND DELANEY RD.

0810 AM     TSTM WND GST     6 SSE BEACH PARK        42.35N 87.81W
07/11/2011  M47.00 MPH       LMZ740             IL   C-MAN STATION

            MEASURED AT WAUKEGAN HARBOR STATION.

0811 AM     TSTM WND DMG     LAKE ZURICH             42.19N 88.09W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            BRANCHES 6 TO 8 INCHES IN DIAMETER DOWN AT THE
            INTERSECTION OF MILLER ROAD AND ROUTE 12.

0812 AM     TSTM WND DMG     CHICAGO                 41.88N 87.63W
07/11/2011                   COOK               IL   PUBLIC

            LARGE TREE APPROXIMATELY 18 INCHES IN DIAMETER DOWN AT
            THE INTERSECTION OF GOETHE ST AND LASALLE ST.

0812 AM     TSTM WND GST     3 SW MIDWAY AIRPORT     41.75N 87.79W
07/11/2011  M75.00 MPH       COOK               IL   CO-OP OBSERVER

0812 AM     TSTM WND DMG     MIDWAY AIRPORT          41.78N 87.75W
07/11/2011                   COOK               IL   BROADCAST MEDIA

            LARGE TREES DOWN NEAR AIRPORT. RELAYED BY FOX CHICAGO.

0812 AM     TSTM WND DMG     LINCOLN PARK            41.93N 87.64W
07/11/2011                   COOK               IL   PUBLIC

            12 INCH DIAMETER TREE LIMB DOWN AT THE INTERSECTION OF
            DAYTON AND WILLOW.

0813 AM     TSTM WND DMG     GURNEE                  42.38N 87.94W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            LARGE BRANCHES OFF TREES. WIND ESTIMATES OF NEAR 60 MPH.

0813 AM     TSTM WND DMG     ROUND LAKE              42.35N 88.11W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            8 INCH DIAMETER TREE SNAPPED OFF AT THE INTERSECTION OF
            ROUTE 60 AND PETERSON RD.

0814 AM     TSTM WND DMG     3 N PALOS HEIGHTS       41.71N 87.80W
07/11/2011                   COOK               IL   EMERGENCY MNGR

            *** 6 INJ *** A FESTIVAL TENT AT 109TH STREET AND 88TH
            AVENUE NEAR MORAINE VALLEY COMMUNITY COLLEGE WAS LIFTED

            AND THEN DROPPED ONTO SIX WORKERS CAUSING MINOR INJURIES.

0814 AM     TSTM WND GST     MIDWAY AIRPORT          41.78N 87.75W
07/11/2011  M75.00 MPH       COOK               IL   ASOS

0815 AM     TSTM WND DMG     MIDWAY AIRPORT          41.78N 87.75W
07/11/2011                   COOK               IL   PUBLIC

            SEMI OVERTURNED ON 65TH AND MENARD. FENCES BLOWN DOWN
            ALONG WITH 10 INCH DIAMETER BRANCHES. SHEET METAL AND
            SHINGLES TORN OFF ROOFS.

0815 AM     TSTM WND DMG     MUNDELEIN               42.27N 88.00W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            MULTIPLE TREE LIMBS 3 TO 4 INCHES IN DIAMETER DOWN.

0815 AM     TSTM WND DMG     ARLINGTON HEIGHTS       42.09N 87.98W
07/11/2011                   COOK               IL   PUBLIC

            12 INCH DIAMETER TREE DOWN.

0815 AM     TSTM WND DMG     PALATINE                42.11N 88.04W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            UP TO 8 INCH TREE BRANCHES DOWN.

0815 AM     TSTM WND DMG     BURBANK                 41.74N 87.77W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            POWER POLES DOWN ON HOMES.

0815 AM     TSTM WND GST     HOMETOWN                41.73N 87.73W
07/11/2011  E65.00 MPH       COOK               IL   PUBLIC

0815 AM     TSTM WND DMG     BURBANK                 41.74N 87.77W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            TREES AND POWER LINES DOWN.

0816 AM     TSTM WND GST     WESTMONT                41.80N 87.97W
07/11/2011  E60.00 MPH       DUPAGE             IL   PUBLIC

            4 INCH DIAMETER TREES DOWN.

0817 AM     TSTM WND DMG     DARIEN                  41.75N 87.98W
07/11/2011                   DUPAGE             IL   TRAINED SPOTTER

            12 TO 15 INCH DIAMETER TREE DOWN.

0817 AM     TSTM WND DMG     TINLEY PARK             41.57N 87.80W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            DELAYED REPORT. TIME APPROXIMATE. 6 INCH DIAMETER LIMB
            DOWN WITH SEVERAL SMALLER LIMBS DOWN THROUGHOUT THE
            NEIGHBORHOOD. NEAR 169TH ST AND MARYLAND DR.

0818 AM     TSTM WND GST     ARLINGTON HEIGHTS       42.09N 87.98W
07/11/2011  E60.00 MPH       COOK               IL   TRAINED SPOTTER

0819 AM     TSTM WND GST     EVERGREEN PARK          41.72N 87.70W
07/11/2011  M72.00 MPH       COOK               IL   TRAINED SPOTTER

0820 AM     TSTM WND DMG     INVERNESS               42.12N 88.10W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            POWER OUTAGES TO TRAFFIC SIGNALS.

0820 AM     MARINE TSTM WIND 4 NE CHICAGO            41.92N 87.57W
07/11/2011  M73.00 MPH       LMZ741             IL   C-MAN STATION

            63 KNOT GUST MEASURED AT CHICAGO CRIB. ANEMOMETER IS
            LOCATED 85 FEET ABOVE LAKE SURFACE. DELAYED REPORT.

0821 AM     TSTM WND DMG     EVERGREEN PARK          41.72N 87.70W
07/11/2011                   COOK               IL   PUBLIC

            AT THE INTERSECTION OF 88TH AND UTICA...THERE IS A 12
            INCH DIAMETER TREE DOWN THAT SNAPPED OFF AT THE BASE.

0822 AM     TSTM WND DMG     GREEN OAKS              42.30N 87.92W
07/11/2011                   LAKE               IL   TRAINED SPOTTER

            SEMI TRUCK BLOWN OVER ON I94 AT RT 176.

0824 AM     MARINE TSTM WIND 4 E CHATHAM             41.73N 87.54W
07/11/2011  M46.00 MPH       COOK               IL   C-MAN STATION

            MEASURED AT CALUMET HARBOR STATION.

0827 AM     TSTM WND GST     LYONS                   41.81N 87.82W
07/11/2011  E60.00 MPH       COOK               IL   PUBLIC

            SOME TREE DAMAGE.

0828 AM     TSTM WND GST     CHICAGO                 41.88N 87.63W
07/11/2011  E60.00 MPH       COOK               IL   TRAINED SPOTTER

            6 INCH TREE LIMB DOWNED.

0830 AM     TSTM WND DMG     EVANSTON                42.05N 87.69W
07/11/2011                   COOK               IL   PUBLIC

            LARGE TREE LIMBS DOWN IN THE STREETS.

0830 AM     MARINE TSTM WIND 4 NE CHICAGO            41.92N 87.57W
07/11/2011  M46.00 MPH       LMZ741             IL   C-MAN STATION

            40 KNOT GUST AT CHICAGO CRIB.

0832 AM     TSTM WND GST     CHICAGO                 41.88N 87.63W
07/11/2011  E55.00 MPH       COOK               IL   TRAINED SPOTTER

0835 AM     TSTM WND DMG     CHICAGO                 41.88N 87.63W
07/11/2011                   COOK               IL   TRAINED SPOTTER

            3 INCH TREE LIMBS DOWN AT INTERSECTION OF W LELAND AVE
            AND NORTH WINCHESTER AVE.

0835 AM     TSTM WND GST     2 SW SCHERERVILLE       41.47N 87.48W
07/11/2011  E50.00 MPH       LAKE               IN   TRAINED SPOTTER

            3 TO 4 INCH LIMBS DOWN.

1100 AM     SEICHE           4 E CHATHAM             41.73N 87.54W
07/11/2011                   COOK               IL   C-MAN STATION

            BEGINNING AROUND 1100 AM CDT...WATER LEVELS MEASURED AT
            CALUMET HARBOR STATION BEGAN FLUCTUATING BY 1 FT OR MORE
            AND CONTINUED TO FLUCTUATE OVER A PERIOD OF ABOUT 3
            HOURS.

1200 PM     SEICHE           2 NNE CHICAGO           41.91N 87.62W
07/11/2011                   LMZ741             IL   PUBLIC

            LIFEGUARDS AT NORTH AVENUE BEACH REPORTED RISING AND
            FALLING LAKE LEVELS ASSOCIATED WITH A SEICHE.


&&

$$

RS