Alert archive / Iowa / Tornado Warnings in 2001

Tornado Warning 10, NWS Sioux Falls, SD

April 30, 2001O'Brien County, Iowa

NWS Sioux Falls, SD issued this tornado warning at Apr 30, 2001, 5:35 PM CDT for O'Brien County, Iowa. It was in force for 25 min. 4 reports came from inside the area while it was in force.

The area

The outline the Iowa Environmental Mesonet reconstructed for it; the warning itself named whole counties, with what was reported inside it.

The facts

Issued: Apr 30, 2001, 5:35 PM CDT (22:35 UTC)
Expired: Apr 30, 2001, 6:00 PM CDT
In force: 25 min
Issued by: NWS Sioux Falls, SD
Area: Whole counties; the outline is the Mesonet’s reconstruction

County O'Brien County, IA

The radar

The Sioux Falls radar (KFSD), 94 km from the middle of the area, began a volume at 22:36 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 was reported inside it

Time	Report	Where
Apr 30, 5:53 PM CDT	Hail 0.75	Sanborn, IA
Apr 30, 5:58 PM CDT	Hail 0.75	Sanborn, IA
Apr 30, 6:08 PM CDT	Hail 0.75	Sheldon, IA
Apr 30, 6:10 PM CDT	Hail 0.88	Sheldon, 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.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.6 hours before the alert went out and 210 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1416 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 255 m²/s²
0-3 km storm-relative helicity: 246 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

000 
WFUS53 KFSD 302236
TORFSD
IAC141-302300-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
535 PM CDT MON APR 30 2001

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* TORNADO WARNING FOR...
  OBRIEN COUNTY IN NORTHWEST IOWA

* UNTIL 600 PM CDT

* AT 535 PM CDT...WEATHER SPOTTERS REPORTED TWO TORNADOES 4 MILES 
  SOUTH OF SHELDON...OR ABOUT 16 MILES NORTHEAST OF ORANGE CITY. THE
  TORNADO PRODUCING STORM WAS MOVING SLOWLY EAST AROUND 15 MPH.

* THE TORNADO WILL BE NEAR...
  ARCHER AROUND 540 PM CDT
  BETWEEN SANBORN AND PRIMGHAR AROUND 600 PM CDT

A TRAINED WEATHER SPOTTER REPORTED TWO TORNADOES 4 MILES SOUTH OF
SHELDON...OR ABOUT 3.5 MILES NORTHWEST OF PAULLINA.

IF YOU ARE IN THE PATH OF THIS TORNADO...TAKE COVER IMMEDIATELY.

LAT...LON 4320 9587 4301 9586 4305 9552 4327 9559

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 30, 5:16 PM CDT	Severe Thunderstorm Warning	FSD	O'Brien, Plymouth, Sioux	44 min
Apr 30, 5:21 PM CDT	Severe Thunderstorm Warning	FSD	Woodbury	24 min
Apr 30, 6:01 PM CDT	Tornado Warning	FSD	O'Brien, Sioux	29 min
Apr 30, 6:04 PM CDT	Severe Thunderstorm Warning	FSD	Woodbury	26 min
Apr 30, 6:29 PM CDT	Severe Thunderstorm Warning	FSD	Woodbury	31 min
Apr 30, 6:46 PM CDT	Severe Thunderstorm Warning	FSD	Sioux	29 min

Nearby

Tornado Warnings in Iowa, 2001 Every tornado warning in 2001 Tornadoes in 2001

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; radar from the NEXRAD Level II archive.