Alert archive / Iowa / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 153, NWS Des Moines, IA

July 21, 2009Calhoun County, Pocahontas County, Webster County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 21, 2009, 6:03 PM CDT for Calhoun County, Pocahontas County, Webster County, Iowa. It was in force for 42 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 21, 2009, 6:03 PM CDT (23:03 UTC)
Expired: Jul 21, 2009, 6:45 PM CDT
In force: 42 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon

Counties Calhoun County, IA, Pocahontas County, IA, Webster County, IA

The radar

The Des Moines radar (KDMX), 108 km from the middle of the area, began a volume at 23:06 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

Minneapolis, MN (KMPX), launched 12:00Z, 11.1 hours before the alert went out and 269 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 187 J/kg
Mixed-layer CIN: -14 J/kg
Mixed-layer LCL: 527 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 87 m²/s²
0-3 km storm-relative helicity: 78 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 21, 2:52 PM CDT, 3 hours 11 minutes earlier.

Area forecast discussion, Jul 21, 2:52 PM CDT, 3 hours 11 minutes before

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Hazardous weather outlook, Jul 21, 4:48 AM CDT, 13 hours 15 minutes before

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In the hours before

Special weather statement, Jul 21, 5:52 PM CDT, 11 minutes before

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Nearby

Severe Thunderstorm Warnings in Iowa, 2009 Every severe thunderstorm warning in 2009

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.