Alert archive / Illinois / Severe Thunderstorm Watches in 2007

Severe Thunderstorm Watch 498

July 9, 200712 counties in Illinois

The Storm Prediction Center issued this severe thunderstorm watch at Jul 9, 2007, 2:23 PM CDT for 12 counties in Illinois. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Jul 9, 2007, 2:23 PM CDT (19:23 UTC)
Expired
Jul 9, 2007, 8:00 PM CDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.5 in
Strongest gust expected
60 kt

Counties Boone County, IL, Cook County, IL, DeKalb County, IL, DuPage County, IL, Kane County, IL, Kendall County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Will County, IL, Winnebago County, IL

The radar

The Chicago radar (KLOT), 80 km from the middle of the area, began a volume at 19:26 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
5%
One or more EF2 to EF5 tornadoes
2%
Ten or more severe wind reports
30%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
20%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
50%

Warnings issued inside it

12 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Jul 9, 2:34 PM CDTSevere Thunderstorm WarningLOTLake56 min
Jul 9, 2:54 PM CDTFlash Flood WarningLOTMcHenry5 hr
Jul 9, 3:19 PM CDTSevere Thunderstorm WarningLOTKane, McHenry56 min
Jul 9, 3:38 PM CDTSevere Thunderstorm WarningLOTDeKalb, Kane52 min
Jul 9, 3:44 PM CDTSevere Thunderstorm WarningLOTCook, DuPage, Kane61 min
Jul 9, 4:07 PM CDTSevere Thunderstorm WarningLOTWill23 min
Jul 9, 4:25 PM CDTFlash Flood WarningLOTDeKalb4 hr
Jul 9, 4:27 PM CDTSevere Thunderstorm WarningLOTDeKalb41 min
Jul 9, 4:48 PM CDTSevere Thunderstorm WarningLOTWill36 min
Jul 9, 4:59 PM CDTSevere Thunderstorm WarningLOTLee46 min
Jul 9, 5:38 PM CDTFlash Flood WarningLOTLee4 hr
Jul 9, 5:49 PM CDTSevere Thunderstorm WarningLOTDeKalb, Kane29 min

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 7.4 hours before the alert went out and 238 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-pSkew-T log-p diagram, Davenport, at 12:00Z on 2007-07-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1065 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 12:00Z on 2007-07-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 27 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
1065 J/kg
Mixed-layer CIN
-50 J/kg
Mixed-layer LCL
1222 m above ground
0-6 km bulk shear
17 kt
0-1 km storm-relative helicity
27 m²/s²
0-3 km storm-relative helicity
-19 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

Nearby

Severe Thunderstorm Watches in Illinois, 2007Every severe thunderstorm watch in 2007

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.