Alert archive / Illinois / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 71, NWS Chicago, IL

July 23, 2009Boone County, DeKalb County, Kane County, Illinois

NWS Chicago, IL issued this severe thunderstorm warning at Jul 23, 2009, 1:59 PM CDT for Boone County, DeKalb County, Kane County, Illinois. It was in force for 30 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 23, 2009, 1:59 PM CDT (18:59 UTC)
Expired: Jul 23, 2009, 2:29 PM CDT
In force: 30 min
Issued by: NWS Chicago, IL
Area: Storm-based polygon

Counties Boone County, IL, DeKalb County, IL, Kane County, IL

The radar

The Chicago radar (KLOT), 70 km from the middle of the area, began a volume at 19:00 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 7.0 hours before the alert went out and 159 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 803 J/kg
Mixed-layer CIN: -24 J/kg
Mixed-layer LCL: 919 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 1 m²/s²
0-3 km storm-relative helicity: 40 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Chicago, IL wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 23, 12:45 PM CDT, 1 hour 14 minutes earlier.

Area forecast discussion, Jul 23, 12:45 PM CDT, 1 hour 14 minutes before

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Hazardous weather outlook, Jul 23, 11:10 AM CDT, 2 hours 49 minutes before

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In the hours before

Local storm report, Jul 23, 1:20 PM CDT, 39 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
120 PM CDT THU JUL 23 2009

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

0119 PM     HAIL             ROCKTON                 42.45N 89.07W
07/23/2009  E0.50 INCH       WINNEBAGO          IL   TRAINED SPOTTER

            HEAVY HAIL FALLING. ALSO WINDS GUSTING TO AROUND 45 MPH.

&&

BOXELL

The office that day

Everything else NWS Chicago, IL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 23, 3:16 PM CDT	Special Weather Statement	LOT	DeKalb	29 min
Jul 23, 3:49 PM CDT	Severe Thunderstorm Warning	LOT	Kankakee, Will	25 min
Jul 23, 4:19 PM CDT	Areal Flood Advisory	LOT	Lake	4 hr
Jul 23, 4:19 PM CDT	Flash Flood Warning	LOT	Cook	3 hr
Jul 23, 4:43 PM CDT	Severe Thunderstorm Warning	LOT	Cook	40 min

Nearby

Severe Thunderstorm Warnings in Illinois, 2009 Every severe thunderstorm warning in 2009

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.