Alert archive / Illinois / Severe Thunderstorm Watches in 2007

Severe Thunderstorm Watch 646

August 23, 200726 counties in Illinois; 5 counties in Indiana; 10 counties in Iowa

The Storm Prediction Center issued this severe thunderstorm watch at Aug 23, 2007, 7:10 PM CDT for 26 counties in Illinois; 5 counties in Indiana; 10 counties in Iowa. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Aug 23, 2007, 7:10 PM CDT (00:10 UTC)
Expired: Aug 24, 2007, 12:00 AM CDT
In force: 5 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 41 counties

Des Moines County, IA, Henry County, IA, Jefferson County, IA, Keokuk County, IA, Lee County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Van Buren County, IA, Washington County, IA, Bureau County, IL, Cook County, IL, Ford County, IL, Fulton County, IL, Grundy County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Iroquois County, IL, Kankakee County, IL, Kendall County, IL, Knox County, IL, LaSalle County, IL, Livingston County, IL, Marshall County, IL, McDonough County, IL, McLean County, IL, Mercer County, IL, Peoria County, IL, Putnam County, IL, Rock Island County, IL, Stark County, IL, Tazewell County, IL, Warren County, IL, Will County, IL, Woodford County, IL, Benton County, IN, Jasper County, IN, Lake County, IN, Newton County, IN, Porter County, IN

The radar

The Quad Cities radar (KDVN), 51 km from the middle of the area, began a volume at 00:12 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: 20%
One or more EF2 to EF5 tornadoes: 5%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 20%
One or more hailstones of 2 inches or more: 10%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Aug 23, 7:10 PM CDT	Severe Thunderstorm Warning	LOT	Lake, Porter	60 min
Aug 23, 7:11 PM CDT	Severe Thunderstorm Warning	DVN	Jefferson	64 min
Aug 23, 7:18 PM CDT	Flash Flood Warning	LOT	Kankakee	4 hr
Aug 23, 7:33 PM CDT	Tornado Warning	LOT	Kankakee	57 min
Aug 23, 7:42 PM CDT	Severe Thunderstorm Warning	LOT	Grundy	30 min
Aug 23, 7:45 PM CDT	Severe Thunderstorm Warning	ILX	Marshall	45 min
Aug 23, 7:46 PM CDT	Severe Thunderstorm Warning	LOT	Jasper, Newton	42 min
Aug 23, 7:50 PM CDT	Severe Thunderstorm Warning	DVN	Henry, Van Buren	73 min
Aug 23, 8:05 PM CDT	Tornado Warning	LOT	Newton	25 min
Aug 23, 8:16 PM CDT	Severe Thunderstorm Warning	LOT	Kankakee, Will	65 min
Aug 23, 8:20 PM CDT	Severe Thunderstorm Warning	DVN	Henderson	55 min
Aug 23, 8:24 PM CDT	Severe Thunderstorm Warning	LOT	Ford, Iroquois	58 min
Aug 23, 8:28 PM CDT	Severe Thunderstorm Warning	DVN	Hancock	62 min
Aug 23, 8:47 PM CDT	Severe Thunderstorm Warning	LOT	Jasper, Lake, Newton, Porter	48 min
Aug 23, 9:20 PM CDT	Flash Flood Warning	LOT	Cook, DeKalb, DuPage, Grundy, Kane, Kankakee and 6 more	7 hr
Aug 23, 9:53 PM CDT	Flash Flood Warning	DVN	Keokuk	6 hr
Aug 23, 10:05 PM CDT	Flash Flood Warning	LOT	Jasper, Newton	6 hr
Aug 23, 10:12 PM CDT	Flash Flood Warning	DVN	Jefferson, Van Buren	6 hr
Aug 23, 10:59 PM CDT	Flash Flood Warning	DVN	Henry	5 hr
Aug 23, 11:46 PM CDT	Flash Flood Warning	DVN	Des Moines, Lee	6 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 0.2 hours before the alert went out and 47 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: 443 J/kg
Mixed-layer CIN: -149 J/kg
Mixed-layer LCL: 1230 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 160 m²/s²
0-3 km storm-relative helicity: 193 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 23, 11:07 PM CDT	Mesoscale Discussion	SPC	Bureau, Grundy, Henderson, Henry, Kankakee, Kendall and 11 more	53 min
Aug 24, 11:12 AM CDT	Mesoscale Discussion	SPC	Bond, Calhoun, Christian, Clay, Clinton, Coles and 24 more	93 min
Aug 24, 12:19 PM CDT	Severe Thunderstorm Watch	SPC	Bond, Calhoun, Cass, Champaign, Christian, Clark and 37 more	8 hr
Aug 24, 2:44 PM CDT	Mesoscale Discussion	SPC	Bond, Champaign, Christian, Clark, Clay, Clinton and 34 more	91 min
Aug 24, 3:04 PM CDT	Severe Thunderstorm Watch	SPC	Ford, Iroquois	7 hr
Aug 24, 5:50 PM CDT	Mesoscale Discussion	SPC	Bond, Champaign, Christian, Clark, Clay, Clinton and 39 more	85 min
Aug 23, 7:30 PM CDT	Mesoscale Discussion	SPC	DeKalb, Elkhart, Kosciusko, LaGrange, Marshall, Noble and 2 more	90 min
Aug 23, 9:54 PM CDT	Mesoscale Discussion	SPC	Allen, DeKalb, Elkhart, Kosciusko, LaGrange, Marshall and 4 more	66 min
Aug 23, 7:47 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Appanoose, Cass, Clarke, Davis and 17 more	118 min
Aug 23, 7:55 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Appanoose, Cass, Clarke, Davis and 17 more	2 hr
Aug 23, 11:01 PM CDT	Mesoscale Discussion	SPC	Adair, Adams, Appanoose, Clarke, Davis, Decatur and 17 more	119 min

Nearby

Severe Thunderstorm Watches in Illinois, 2007 Severe Thunderstorm Watches in Iowa, 2007 Severe Thunderstorm Watches in Indiana, 2007 Every 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.