Alert archive / Iowa / Mesoscale Discussions in 2011

Mesoscale Discussion 842

May 21, 201148 counties in Iowa; Atchison County, Missouri; 18 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at May 21, 2011, 6:07 PM CDT for 48 counties in Iowa; Atchison County, Missouri; 18 counties in Nebraska. It was in force for 53 min.

The area

The outline as issued.

The facts

Issued
May 21, 2011, 6:07 PM CDT (23:07 UTC)
Expired
May 21, 2011, 7:00 PM CDT
In force
53 min
Issued by
the Storm Prediction Center
All 67 counties

Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Buena Vista County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cerro Gordo County, IA, Cherokee County, IA, Clarke County, IA, Clay County, IA, Crawford County, IA, Dallas County, IA, Decatur County, IA, Dickinson County, IA, Emmet County, IA, Fremont County, IA, Greene County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Harrison County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Madison County, IA, Mills County, IA, Monona County, IA, Montgomery County, IA, O'Brien County, IA, Osceola County, IA, Page County, IA, Palo Alto County, IA, Plymouth County, IA, Pocahontas County, IA, Pottawattamie County, IA, Ringgold County, IA, Sac County, IA, Shelby County, IA, Sioux County, IA, Taylor County, IA, Union County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Atchison County, MO, Burt County, NE, Cass County, NE, Dodge County, NE, Douglas County, NE, Gage County, NE, Jefferson County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Otoe County, NE, Pawnee County, NE, Richardson County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, Thurston County, NE, Washington County, NE

The radar

The Omaha radar (KOAX), 109 km from the middle of the area, began a volume at 23:07 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.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.1 hours before the alert went out and 110 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 12:00Z on 2011-05-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1247 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 12:00Z on 2011-05-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -6 square meters per square second.1939587897117Sfc1 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
1247 J/kg
Mixed-layer CIN
-16 J/kg
Mixed-layer LCL
607 m above ground
0-6 km bulk shear
50 kt
0-1 km storm-relative helicity
-6 m²/s²
0-3 km storm-relative helicity
-20 m²/s²
Significant tornado parameter
-0.1
Supercell composite
-0.4

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 21, 12:51 PM CDTMesoscale DiscussionSPCAdair, Adams, Audubon, Boone, Buena Vista, Calhoun and 31 more114 min
May 21, 2:25 PM CDTSevere Thunderstorm WatchSPCAdair, Adams, Appanoose, Audubon, Boone, Buena Vista and 49 more10 hr
May 21, 5:25 PM CDTMesoscale DiscussionSPCAdams, Appanoose, Clarke, Davis, Decatur, Fremont and 9 more65 min
May 21, 2:33 PM CDTMesoscale DiscussionSPCAndrew, Atchison, Buchanan, Clay, Clinton, DeKalb and 4 more87 min
May 21, 5:34 PM CDTSevere Thunderstorm WatchSPCAdair, Andrew, Atchison, Buchanan, Caldwell, Carroll and 26 more7 hr
May 21, 3:41 PM CDTSevere Thunderstorm WatchSPCAdams, Clay, Fillmore, Franklin, Greeley, Hall and 10 more9 hr

Nearby

Mesoscale Discussions in Iowa, 2011Mesoscale Discussions in Nebraska, 2011Mesoscale Discussions in Missouri, 2011Every mesoscale discussion 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.