Alert archive / Iowa / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 798
The Storm Prediction Center issued this severe thunderstorm watch at Aug 23, 2011, 3:00 AM CDT for 30 counties in Iowa; 7 counties in Minnesota. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 23, 2011, 3:00 AM CDT (08:00 UTC)
- Expired
- Aug 23, 2011, 8:55 AM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 37 counties
Allamakee County, IA, Benton County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clayton County, IA, Delaware County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Grundy County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Howard County, IA, Humboldt County, IA, Linn County, IA, Marshall County, IA, Mitchell County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winnebago County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Dodge County, MN, Fillmore County, MN, Houston County, MN, Mower County, MN, Olmsted County, MN, Wabasha County, MN, Winona County, MN
The radar
The Des Moines radar (KDMX), 142 km from the middle of the area, began a volume at 08:03 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
- 30%
- 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
7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 3:14 AM CDT | Severe Thunderstorm Warning | DMX | Franklin, Hamilton, Hardin, Webster, Wright | 61 min |
| Aug 23, 4:02 AM CDT | Severe Thunderstorm Warning | ARX | Fillmore, Houston, Winona | 43 min |
| Aug 23, 4:25 AM CDT | Severe Thunderstorm Warning | ARX | Allamakee, Clayton, Fayette, Winneshiek | 50 min |
| Aug 23, 5:55 AM CDT | Severe Thunderstorm Warning | DMX | Hamilton | 35 min |
| Aug 23, 6:18 AM CDT | Severe Thunderstorm Warning | DMX | Hardin | 21 min |
| Aug 23, 6:23 AM CDT | Severe Thunderstorm Warning | DMX | Cerro Gordo, Hancock, Kossuth, Winnebago, Worth | 37 min |
| Aug 23, 6:57 AM CDT | Severe Thunderstorm Warning | DMX | Cerro Gordo, Worth | 34 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 00:00Z, 8.0 hours before the alert went out and 229 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2096 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- -21 m²/s²
- 0-3 km storm-relative helicity
- 94 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 23, 12:45 AM CDT | Mesoscale Discussion | SPC | Adair, Adams, Audubon, Benton, Black Hawk, Boone and 56 more | 2 hr |
| Aug 23, 4:55 AM CDT | Mesoscale Discussion | SPC | Allamakee, Benton, Black Hawk, Bremer, Buchanan, Butler and 23 more | 2 hr |
| Aug 23, 3:10 AM CDT | Mesoscale Discussion | SPC | Anoka, Benton, Carver, Chippewa, Chisago, Hennepin and 21 more | 2 hr |
| Aug 23, 3:34 AM CDT | Severe Thunderstorm Watch | SPC | Anoka, Benton, Blue Earth, Brown, Carver, Chippewa and 34 more | 4 hr |
| Aug 23, 4:56 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Calumet, Clark, Fond du Lac, Green Lake and 12 more | 94 min |
| Aug 23, 5:19 PM CDT | Tornado Watch | SPC | Adams, Brown, Calumet, Columbia, Dodge, Fond du Lac and 20 more | 6 hr |
Nearby
Severe Thunderstorm Watches in Iowa, 2011Severe Thunderstorm Watches in Minnesota, 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.