Alert archive / Nebraska / Tornado Warnings in 2001

Tornado Warning 4, NWS Sioux Falls, SD

April 20, 2001Dakota County, Dixon County, Nebraska

NWS Sioux Falls, SD issued this tornado warning at Apr 20, 2001, 7:32 PM CDT for Dakota County, Dixon County, Nebraska. It was in force for 28 min. 3 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 20, 2001, 7:32 PM CDT (00:32 UTC)
Expired: Apr 20, 2001, 8:00 PM CDT
In force: 28 min
Issued by: NWS Sioux Falls, SD
Area: Whole counties; the outline is the Mesonet’s reconstruction

Counties Dakota County, NE, Dixon County, NE

The radar

The Omaha radar (KOAX), 122 km from the middle of the area, began a volume at 00:35 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 20, 7:39 PM CDT	Hail 1.75	Emerson, NE
Apr 20, 7:41 PM CDT	Hail 1	Emerson, NE
Apr 20, 8:10 PM CDT	Hail 0.75	Willis, NE

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 00:00Z, 0.5 hours before the alert went out and 122 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: 939 J/kg
Mixed-layer CIN: -84 J/kg
Mixed-layer LCL: 1568 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 119 m²/s²
0-3 km storm-relative helicity: 247 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 4.8

Open this sounding in Storm Lab

The text

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

498 
WFUS53 KFSD 210033
TORFSD
NEC043-051-210100-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
732 PM CDT FRI APR 20 2001

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* TORNADO WARNING FOR...
  DAKOTA COUNTY IN NORTHEAST NEBRASKA
  SOUTHEAST DIXON COUNTY IN NORTHEAST NEBRASKA

* UNTIL 800 PM CDT

* AT 732 PM CDT...DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM 9
  MILES SOUTHWEST OF HUBBARD...OR ABOUT 17 MILES SOUTH OF PONCA...
  MOVING NORTHEAST AT 20 MPH.

* THE TORNADO WILL BE NEAR...
  HUBBARD AROUND 745 PM CDT
  JACKSON AROUND 755 PM CDT

THIS WARNING REPLACES THE SEVERE THUNDERSTORM WARNING PREVIOUSLY 
ISSUED FOR THE WARNED AREA.  A NATIONAL WEATHER SERVICE EMPLOYEE 
REPORTED A FUNNEL CLOUD 1 MILE NORTHWEST OF EMERSON WITH THIS STORM.

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

LAT...LON 4233 9690 4226 9670 4247 9640 4255 9667

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 20, 7:19 PM CDT	Severe Thunderstorm Warning	FSD	Dakota, Dixon	26 min
Apr 20, 7:59 PM CDT	Severe Thunderstorm Warning	FSD	Dakota	31 min
Apr 20, 8:28 PM CDT	Severe Thunderstorm Warning	FSD	Dixon	32 min
Apr 20, 9:04 PM CDT	Tornado Warning	FSD	Dixon	26 min
Apr 20, 10:32 PM CDT	Severe Thunderstorm Warning	FSD	Dakota	28 min

Nearby

Tornado Warnings in Nebraska, 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.