Alert archive / Iowa / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 663

July 11, 201144 counties in Iowa

The Storm Prediction Center issued this severe thunderstorm watch at Jul 11, 2011, 1:08 AM CDT for 44 counties in Iowa. It was in force for 13 min.

The area

The outline as issued.

The facts

Issued
Jul 11, 2011, 1:08 AM CDT (06:08 UTC)
Expired
Jul 11, 2011, 1:21 AM CDT
In force
13 min
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 06:09 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

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

IssuedProductOfficeCountiesLasted
Jul 11, 1:12 AM CDTSevere Thunderstorm WarningDMXEmmet, Kossuth, Palo Alto48 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, 6.1 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.

Skew-T log-pSkew-T log-p diagram, Omaha, NE at 00:00Z on 2011-07-11Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 4133 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Omaha, NE at 00:00Z on 2011-07-11The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 25 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
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

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 10, 7:51 PM CDTMesoscale DiscussionSPCAllamakee, Howard, Mitchell, Winneshiek84 min
Jul 10, 9:53 PM CDTMesoscale DiscussionSPCAllamakee, Cerro Gordo, Chickasaw, Dickinson, Emmet, Floyd and 9 more67 min
Jul 10, 10:10 PM CDTSevere Thunderstorm WatchSPCAllamakee, Black Hawk, Bremer, Butler, Cerro Gordo, Chickasaw and 13 more6 hr
Jul 10, 10:27 PM CDTMesoscale DiscussionSPCCherokee, Harrison, Monona, Plymouth, Sioux, Woodbury63 min
Jul 10, 10:57 PM CDTSevere Thunderstorm WatchSPCHarrison, Mills, Monona, Montgomery, Pottawattamie, Shelby4 hr
Jul 10, 11:45 PM CDTMesoscale DiscussionSPCAllamakee, Bremer, Cerro Gordo, Chickasaw, Clayton, Delaware and 8 more90 min
Jul 10, 11:56 PM CDTSevere Thunderstorm WatchSPCBuena Vista, Cherokee, Clay, Dickinson, Ida, Lyon and 5 more4 hr
Jul 11, 1:21 AM CDTSevere Thunderstorm WatchSPCAdair, Adams, Audubon, Black Hawk, Boone, Bremer and 38 more4 hr
Jul 11, 2:36 AM CDTMesoscale DiscussionSPCAdair, Adams, Benton, Black Hawk, Boone, Bremer and 52 more114 min
Jul 11, 3:30 AM CDTSevere Thunderstorm WatchSPCAllamakee, Benton, Buchanan, Cedar, Chickasaw, Clayton and 18 more6 hr
Jul 11, 5:07 AM CDTMesoscale DiscussionSPCBenton, Black Hawk, Buchanan, Cedar, Clayton, Clinton and 15 more113 min
Jul 10, 7:21 PM CDTMesoscale DiscussionSPCAdams, Blaine, Brown, Buffalo, Chase, Custer and 29 more84 min
Jul 10, 7:24 PM CDTSevere Thunderstorm WatchSPCAdams, Blaine, Boyd, Brown, Buffalo, Chase and 38 more6 hr
Jul 11, 2:50 PM CDTMesoscale DiscussionSPCArthur, Banner, Box Butte, Cheyenne, Dawes, Deuel and 8 more85 min
Jul 11, 3:07 PM CDTSevere Thunderstorm WatchSPCBanner, Box Butte, Cheyenne, Dawes, Deuel, Garden and 5 more7 hr
Jul 11, 5:01 PM CDTMesoscale DiscussionSPCCherry, Dawes, Sheridan29 min
Jul 11, 5:06 PM CDTTornado WatchSPCBox Butte, Cherry, Dawes, Sheridan, Sioux5 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.