Alert archive / Iowa / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 623
The Storm Prediction Center issued this severe thunderstorm watch at Jul 11, 2011, 1:21 AM CDT for 44 counties in Iowa. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 11, 2011, 1:21 AM CDT (06:21 UTC)
- Expired
- Jul 11, 2011, 5:22 AM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 44 counties
Adair County, IA, Adams County, IA, Audubon County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cerro Gordo County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Emmet County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Humboldt County, IA, Jasper County, IA, Kossuth County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Sac County, IA, Story County, IA, Tama County, IA, Union County, IA, Warren County, IA, Webster County, IA, Winnebago County, IA, Worth County, IA, Wright County, IA
The radar
The Des Moines radar (KDMX), 70 km from the middle of the area, began a volume at 06:23 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
- 20%
- 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
11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 11, 2:10 AM CDT | Severe Thunderstorm Warning | DMX | Adair, Audubon, Cass, Guthrie | 50 min |
| Jul 11, 2:24 AM CDT | Severe Thunderstorm Warning | DMX | Cerro Gordo, Hancock, Winnebago, Worth | 51 min |
| Jul 11, 2:41 AM CDT | Severe Thunderstorm Warning | DMX | Adair, Dallas, Guthrie, Madison, Polk, Warren | 49 min |
| Jul 11, 2:52 AM CDT | Severe Thunderstorm Warning | DMX | Hamilton, Humboldt, Webster, Wright | 38 min |
| Jul 11, 3:25 AM CDT | Severe Thunderstorm Warning | DMX | Boone, Marshall, Story | 50 min |
| Jul 11, 3:34 AM CDT | Severe Thunderstorm Warning | DMX | Jasper, Marion, Marshall, Polk, Story, Warren | 41 min |
| Jul 11, 3:53 AM CDT | Tornado Warning | DMX | Marshall, Story | 37 min |
| Jul 11, 4:02 AM CDT | Severe Thunderstorm Warning | DMX | Jasper, Marshall, Poweshiek, Tama | 43 min |
| Jul 11, 4:18 AM CDT | Severe Thunderstorm Warning | DMX | Black Hawk, Tama | 42 min |
| Jul 11, 4:32 AM CDT | Tornado Warning | DMX | Marshall, Tama | 28 min |
| Jul 11, 4:57 AM CDT | Severe Thunderstorm Warning | DMX | Black Hawk | 18 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
Omaha, NE (KOAX), launched 00:00Z, 6.4 hours before the alert went out and 173 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.
- Mixed-layer CAPE
- 4133 J/kg
- Mixed-layer CIN
- -75 J/kg
- Mixed-layer LCL
- 1304 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 25 m²/s²
- 0-3 km storm-relative helicity
- 62 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 3.7
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 10, 7:51 PM CDT | Mesoscale Discussion | SPC | Allamakee, Howard, Mitchell, Winneshiek | 84 min |
| Jul 10, 9:53 PM CDT | Mesoscale Discussion | SPC | Allamakee, Cerro Gordo, Chickasaw, Dickinson, Emmet, Floyd and 9 more | 67 min |
| Jul 10, 10:10 PM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Black Hawk, Bremer, Butler, Cerro Gordo, Chickasaw and 13 more | 6 hr |
| Jul 10, 10:27 PM CDT | Mesoscale Discussion | SPC | Cherokee, Harrison, Monona, Plymouth, Sioux, Woodbury | 63 min |
| Jul 10, 10:57 PM CDT | Severe Thunderstorm Watch | SPC | Harrison, Mills, Monona, Montgomery, Pottawattamie, Shelby | 4 hr |
| Jul 10, 11:45 PM CDT | Mesoscale Discussion | SPC | Allamakee, Bremer, Cerro Gordo, Chickasaw, Clayton, Delaware and 8 more | 90 min |
| Jul 10, 11:56 PM CDT | Severe Thunderstorm Watch | SPC | Buena Vista, Cherokee, Clay, Dickinson, Ida, Lyon and 5 more | 4 hr |
| Jul 11, 1:08 AM CDT | Severe Thunderstorm Watch | SPC | Adair, Adams, Audubon, Black Hawk, Boone, Bremer and 38 more | 13 min |
| Jul 11, 2:36 AM CDT | Mesoscale Discussion | SPC | Adair, Adams, Benton, Black Hawk, Boone, Bremer and 52 more | 114 min |
| Jul 11, 3:30 AM CDT | Severe Thunderstorm Watch | SPC | Allamakee, Benton, Buchanan, Cedar, Chickasaw, Clayton and 18 more | 6 hr |
| Jul 11, 5:07 AM CDT | Mesoscale Discussion | SPC | Benton, Black Hawk, Buchanan, Cedar, Clayton, Clinton and 15 more | 113 min |
| Jul 10, 7:21 PM CDT | Mesoscale Discussion | SPC | Adams, Blaine, Brown, Buffalo, Chase, Custer and 29 more | 84 min |
| Jul 10, 7:24 PM CDT | Severe Thunderstorm Watch | SPC | Adams, Blaine, Boyd, Brown, Buffalo, Chase and 38 more | 6 hr |
| Jul 11, 2:50 PM CDT | Mesoscale Discussion | SPC | Arthur, Banner, Box Butte, Cheyenne, Dawes, Deuel and 8 more | 85 min |
| Jul 11, 3:07 PM CDT | Severe Thunderstorm Watch | SPC | Banner, Box Butte, Cheyenne, Dawes, Deuel, Garden and 5 more | 7 hr |
| Jul 11, 5:01 PM CDT | Mesoscale Discussion | SPC | Cherry, Dawes, Sheridan | 29 min |
| Jul 11, 5:06 PM CDT | Tornado Watch | SPC | Box Butte, Cherry, Dawes, Sheridan, Sioux | 5 hr |
Nearby
Severe Thunderstorm Watches in Iowa, 2011Every severe thunderstorm watch in 2011
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.