Alert archive / Iowa / Severe Thunderstorm Watches in 2007

Severe Thunderstorm Watch 439

June 21, 20074 states

The Storm Prediction Center issued this severe thunderstorm watch at Jun 21, 2007, 6:47 PM CDT for 4 states. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Jun 21, 2007, 6:47 PM CDT (23:47 UTC)
Expired: Jun 21, 2007, 11:10 PM CDT
In force: 4 hr
Issued by: the Storm Prediction Center
Largest hail expected: 2 in
Strongest gust expected: 60 kt

All 46 counties

Appanoose County, IA, Cedar County, IA, Clayton County, IA, Clinton County, IA, Davis County, IA, Delaware County, IA, Des Moines County, IA, Dubuque County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Lee County, IA, Linn County, IA, Louisa County, IA, Monroe County, IA, Muscatine County, IA, Scott County, IA, Van Buren County, IA, Wapello County, IA, Washington County, IA, Carroll County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Knox County, IL, McDonough County, IL, Mercer County, IL, Rock Island County, IL, Stephenson County, IL, Warren County, IL, Whiteside County, IL, Clark County, MO, Scotland County, MO, Crawford County, WI, Dane County, WI, Grant County, WI, Green County, WI, Iowa County, WI, Lafayette County, WI, Richland County, WI, Sauk County, WI

The radar

The Quad Cities radar (KDVN), 71 km from the middle of the area, began a volume at 23:50 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: 10%
One or more EF2 to EF5 tornadoes: 2%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 30%
Ten or more severe hail reports: 30%
One or more hailstones of 2 inches or more: 20%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Jun 21, 6:58 PM CDT	Severe Thunderstorm Warning	MKX	Dane	77 min
Jun 21, 7:23 PM CDT	Severe Thunderstorm Warning	DVN	Cedar, Johnson	67 min
Jun 21, 7:37 PM CDT	Severe Thunderstorm Warning	DMX	Davis	39 min
Jun 21, 7:38 PM CDT	Severe Thunderstorm Warning	DVN	Johnson, Louisa, Muscatine, Washington	52 min
Jun 21, 7:40 PM CDT	Severe Thunderstorm Warning	ILX	Knox	50 min
Jun 21, 7:56 PM CDT	Severe Thunderstorm Warning	DVN	McDonough	34 min
Jun 21, 8:05 PM CDT	Severe Thunderstorm Warning	ARX	Grant	23 min
Jun 21, 8:07 PM CDT	Severe Thunderstorm Warning	DVN	Rock Island	38 min
Jun 21, 8:12 PM CDT	Severe Thunderstorm Warning	MKX	Iowa, Sauk	49 min
Jun 21, 8:22 PM CDT	Severe Thunderstorm Warning	DVN	Henderson	23 min
Jun 21, 8:24 PM CDT	Severe Thunderstorm Warning	ILX	Knox, Peoria	51 min
Jun 21, 8:30 PM CDT	Severe Thunderstorm Warning	DVN	McDonough	45 min
Jun 21, 8:41 PM CDT	Severe Thunderstorm Warning	DVN	Warren	35 min
Jun 21, 8:57 PM CDT	Severe Thunderstorm Warning	ILX	Fulton, Knox	48 min
Jun 21, 9:10 PM CDT	Severe Thunderstorm Warning	DVN	Hancock	35 min

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 12:00Z, 11.8 hours before the alert went out and 74 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: 683 J/kg
Mixed-layer CIN: -148 J/kg
Mixed-layer LCL: 1072 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 64 m²/s²
0-3 km storm-relative helicity: 23 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 21, 9:57 AM CDT	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, Champaign, Cook, DeKalb and 42 more	33 min
Jun 21, 12:27 PM CDT	Mesoscale Discussion	SPC	Boone, Carroll, DeKalb, Jo Daviess, Kane, McHenry and 3 more	63 min
Jun 21, 3:25 PM CDT	Mesoscale Discussion	SPC	Jo Daviess	35 min
Jun 21, 3:55 PM CDT	Severe Thunderstorm Watch	SPC	Henderson, Mercer, Rock Island, Warren	3 hr
Jun 21, 5:42 PM CDT	Mesoscale Discussion	SPC	Bureau, Carroll, Fulton, Henderson, Henry, Jo Daviess and 15 more	93 min
Jun 20, 11:30 PM CDT	Mesoscale Discussion	SPC	Howard, Mitchell, Winnebago, Worth	90 min
Jun 21, 4:27 AM CDT	Severe Thunderstorm Watch	SPC	Allamakee, Howard, Mitchell, Winneshiek	8 hr
Jun 21, 9:10 AM CDT	Mesoscale Discussion	SPC	Clay, Dickinson, Lyon, O'Brien, Osceola, Sioux	35 min
Jun 21, 9:38 AM CDT	Severe Thunderstorm Watch	SPC	Buena Vista, Cherokee, Clay, Dickinson, Ida, Lyon and 5 more	6 hr
Jun 21, 11:55 AM CDT	Mesoscale Discussion	SPC	Allamakee, Black Hawk, Bremer, Buchanan, Butler, Cerro Gordo and 16 more	50 min
Jun 21, 11:59 AM CDT	Severe Thunderstorm Watch	SPC	Allamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 36 more	8 hr
Jun 21, 2:13 PM CDT	Mesoscale Discussion	SPC	Allamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 50 more	62 min
Jun 21, 3:15 PM CDT	Mesoscale Discussion	SPC	Cherokee, Clay, Dickinson, Ida, Lyon, O'Brien and 4 more	30 min
Jun 20, 7:25 PM CDT	Mesoscale Discussion	SPC	Adams, Barron, Buffalo, Chippewa, Clark, Dunn and 18 more	95 min

Nearby

Severe Thunderstorm Watches in Iowa, 2007 Severe Thunderstorm Watches in Illinois, 2007 Severe Thunderstorm Watches in Wisconsin, 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.