Alert archive / Iowa / Tornado Warnings in 1991

Tornado Warning 9, NWS Omaha, NE

April 29, 1991Harrison County, Pottawattamie County, Shelby County, Iowa

NWS Omaha, NE issued this tornado warning at Apr 29, 1991, 1:54 PM CDT for Harrison County, Pottawattamie County, Shelby County, Iowa. It was in force for 36 min. 2 reports came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued
Apr 29, 1991, 1:54 PM CDT (18:54 UTC)
Expired
Apr 29, 1991, 2:30 PM CDT
In force
36 min
Issued by
NWS Omaha, NE
Area
Whole counties

Counties Harrison County, IA, Pottawattamie County, IA, Shelby County, IA

What was reported inside it

TimeReportWhereRemark
Apr 29, 1:58 PM CDTTornado F1Harrison, IA
Apr 29, 2:21 PM CDTTornado F0Pottawattamie, IA

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in. Storm Data before 1996 records only tornadoes, thunderstorm wind and hail.

The nearest sounding before it

Omaha, NE (KOVN), launched 12:00Z, 6.9 hours before the alert went out and 73 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 1991-04-29Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 298 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 1991-04-29The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -139 square meters per square second.1939587897117136Sfc1 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
298 J/kg
Mixed-layer CIN
-51 J/kg
Mixed-layer LCL
732 m above ground
0-6 km bulk shear
50 kt
0-1 km storm-relative helicity
-139 m²/s²
0-3 km storm-relative helicity
-100 m²/s²
Significant tornado parameter
-0.1
Supercell composite
-1.0

Open this sounding in Storm Lab

The text

The text of this product is not in the archive. The NWS text archive before 2002 is incomplete.

The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 29, 1:17 PM CDTSevere Thunderstorm WarningOAXDouglas, Sarpy58 min
Apr 29, 1:23 PM CDTTornado WarningOAXDouglas37 min
Apr 29, 2:31 PM CDTSevere Thunderstorm WarningOAXWashington59 min
Apr 29, 1:14 PM CDTSevere Thunderstorm WarningOAXHarrison61 min
Apr 29, 2:31 PM CDTSevere Thunderstorm WarningOAXHarrison, Pottawattamie, Shelby39 min

Nearby

Tornado Warnings in Iowa, 1991Every tornado warning in 1991Tornadoes in 1991

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive.