Alert archive / Iowa / Severe Thunderstorm Watches in 2011
Severe Thunderstorm Watch 733
The Storm Prediction Center issued this severe thunderstorm watch at Aug 6, 2011, 10:14 PM CDT for 9 counties in Illinois; 22 counties in Iowa; 20 counties in Missouri. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 6, 2011, 10:14 PM CDT (03:14 UTC)
- Expired
- Aug 7, 2011, 3:32 AM CDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 51 counties
Appanoose County, IA, Cedar County, IA, Davis County, IA, Des Moines County, IA, Henry County, IA, Iowa County, IA, Jefferson County, IA, Johnson County, IA, Keokuk County, IA, Lee County, IA, Louisa County, IA, Lucas County, IA, Mahaska County, IA, Marion County, IA, Monroe County, IA, Muscatine County, IA, Scott County, IA, Van Buren County, IA, Wapello County, IA, Warren County, IA, Washington County, IA, Wayne County, IA, Adams County, IL, Brown County, IL, Hancock County, IL, Henderson County, IL, McDonough County, IL, Mercer County, IL, Pike County, IL, Rock Island County, IL, Warren County, IL, Adair County, MO, Chariton County, MO, Clark County, MO, Grundy County, MO, Knox County, MO, Lewis County, MO, Linn County, MO, Livingston County, MO, Macon County, MO, Marion County, MO, Mercer County, MO, Monroe County, MO, Pike County, MO, Putnam County, MO, Ralls County, MO, Randolph County, MO, Schuyler County, MO, Scotland County, MO, Shelby County, MO, Sullivan County, MO
The radar
The Des Moines radar (KDMX), 188 km from the middle of the area, began a volume at 03:14 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
- 5%
- Ten or more severe wind reports
- 70%
- 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
- 80%
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 |
|---|---|---|---|---|
| Aug 6, 10:46 PM CDT | Severe Thunderstorm Warning | DMX | Clarke, Madison, Warren | 29 min |
| Aug 6, 11:07 PM CDT | Severe Thunderstorm Warning | EAX | Grundy, Harrison, Mercer, Putnam, Sullivan | 38 min |
| Aug 6, 11:08 PM CDT | Severe Thunderstorm Warning | DMX | Lucas, Wayne | 52 min |
| Aug 6, 11:09 PM CDT | Severe Thunderstorm Warning | DMX | Clarke, Jasper, Lucas, Madison, Marion, Polk and 1 more | 51 min |
| Aug 6, 11:32 PM CDT | Severe Thunderstorm Warning | DMX | Appanoose, Monroe | 43 min |
| Aug 6, 11:36 PM CDT | Tornado Warning | DMX | Lucas, Marion, Monroe | 24 min |
| Aug 6, 11:48 PM CDT | Severe Thunderstorm Warning | DMX | Jasper, Mahaska, Marion, Poweshiek | 57 min |
| Aug 7, 12:02 AM CDT | Severe Thunderstorm Warning | DMX | Davis, Wapello | 58 min |
| Aug 7, 12:20 AM CDT | Severe Thunderstorm Warning | DVN | Henry, Iowa, Jefferson, Johnson, Keokuk, Lee and 2 more | 55 min |
| Aug 7, 1:14 AM CDT | Severe Thunderstorm Warning | DVN | Hancock, Henderson, McDonough, Mercer, Rock Island, Warren | 61 min |
| Aug 7, 1:55 AM CDT | Severe Thunderstorm Warning | DVN | Bureau, Henry, Mercer, Rock Island, Whiteside | 50 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, 3.2 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
- 1118 J/kg
- Mixed-layer CIN
- -22 J/kg
- Mixed-layer LCL
- 1057 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 41 m²/s²
- 0-3 km storm-relative helicity
- 108 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 5.1
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 6, 11:06 PM CDT | Mesoscale Discussion | SPC | Adams, Brown, Fulton, Hancock, Henderson, McDonough and 4 more | 114 min |
| Aug 7, 11:14 AM CDT | Mesoscale Discussion | SPC | Champaign, Clark, Coles, Crawford, Cumberland, Douglas and 8 more | 2 hr |
| Aug 7, 5:20 PM CDT | Mesoscale Discussion | SPC | Bond, Calhoun, Clinton, Franklin, Jackson, Jefferson and 10 more | 115 min |
| Aug 7, 5:41 PM CDT | Severe Thunderstorm Watch | SPC | Alexander, Bond, Calhoun, Clinton, Edwards, Franklin and 23 more | 6 hr |
| Aug 6, 8:10 PM CDT | Mesoscale Discussion | SPC | Adair, Adams, Appanoose, Audubon, Benton, Black Hawk and 45 more | 2 hr |
| Aug 7, 10:48 AM CDT | Mesoscale Discussion | SPC | Platte | 117 min |
| Aug 7, 12:55 PM CDT | Severe Thunderstorm Watch | SPC | Bates, Buchanan, Caldwell, Carroll, Cass, Clay and 11 more | 5 hr |
| Aug 7, 3:16 PM CDT | Mesoscale Discussion | SPC | Barton, Bates, Benton, Camden, Carroll, Cass and 24 more | 119 min |
| Aug 7, 3:29 PM CDT | Severe Thunderstorm Watch | SPC | Barton, Benton, Boone, Callaway, Camden, Cedar and 18 more | 6 hr |
| Aug 7, 6:07 PM CDT | Severe Thunderstorm Watch | SPC | Barry, Christian, Douglas, Greene, Howell, Jasper and 11 more | 5 hr |
Nearby
Severe Thunderstorm Watches in Iowa, 2011Severe Thunderstorm Watches in Missouri, 2011Severe Thunderstorm Watches in Illinois, 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.