Alert archive / Iowa / Tornado Warnings in 2012

Tornado Warning 14, NWS Sioux Falls, SD

May 1, 2012Lyon County, Iowa

NWS Sioux Falls, SD issued this tornado warning at May 1, 2012, 7:57 PM CDT for Lyon County, Iowa. It was in force for 33 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
May 1, 2012, 7:57 PM CDT (00:57 UTC)
Expired
May 1, 2012, 8:30 PM CDT
In force
33 min
Issued by
NWS Sioux Falls, SD
Area
Storm-based polygon

County Lyon County, IA

The radar

The Sioux Falls radar (KFSD), 57 km from the middle of the area, began a volume at 00:58 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

IssuedProductOfficeLasted
May 1, 2:59 PM CDTTornado WatchSPC6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 1.0 hours before the alert went out and 220 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 00:00Z on 2012-05-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1502 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 00:00Z on 2012-05-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 75 square meters per square second.193958Sfc1 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
1502 J/kg
Mixed-layer CIN
-30 J/kg
Mixed-layer LCL
1477 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
75 m²/s²
0-3 km storm-relative helicity
122 m²/s²
Significant tornado parameter
0.4
Supercell composite
5.2

Open this sounding in Storm Lab

The text

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

366 
WFUS53 KFSD 020057
TORFSD
IAC119-020130-
/O.NEW.KFSD.TO.W.0014.120502T0057Z-120502T0130Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
757 PM CDT TUE MAY 1 2012

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* TORNADO WARNING FOR...
  SOUTH CENTRAL LYON COUNTY IN NORTHWEST IOWA...

* UNTIL 830 PM CDT

* AT 757 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE
  TRACKING A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS
  DANGEROUS STORM WAS LOCATED NEAR DOON...OR 11 MILES SOUTH OF ROCK
  RAPIDS...AND MOVING NORTHEAST AT 35 MPH.

* THIS TORNADIC STORM WILL AFFECT MAINLY RURAL AREAS OF SOUTH CENTRAL
  LYON COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR
OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.

&&

LAT...LON 4326 9616 4326 9625 4328 9627 4339 9608
      4328 9605
TIME...MOT...LOC 0057Z 228DEG 30KT 4329 9621

$$

CJ
3 follow-up statements
109 
WWUS53 KFSD 020105
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
805 PM CDT TUE MAY 1 2012

IAC119-020130-
/O.CON.KFSD.TO.W.0014.000000T0000Z-120502T0130Z/
LYON IA-
805 PM CDT TUE MAY 1 2012

...A TORNADO WARNING REMAINS IN EFFECT FOR SOUTH CENTRAL LYON COUNTY
UNTIL 830 PM CDT...

AT 805 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE TRACKING
A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO.  THIS DANGEROUS
STORM WAS LOCATED JUST SOUTHEAST OF DOON...OR 11 MILES SOUTH OF ROCK 
RAPIDS...MOVING EAST AT 20 MPH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR
OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.

&&

LAT...LON 4326 9616 4326 9620 4329 9622 4339 9608
      4328 9605
TIME...MOT...LOC 0105Z 260DEG 17KT 4328 9618

$$

CJ
940 
WWUS53 KFSD 020116
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
816 PM CDT TUE MAY 1 2012

IAC119-020130-
/O.CON.KFSD.TO.W.0014.000000T0000Z-120502T0130Z/
LYON IA-
816 PM CDT TUE MAY 1 2012

...A TORNADO WARNING REMAINS IN EFFECT FOR SOUTH CENTRAL LYON COUNTY
UNTIL 830 PM CDT...

AT 816 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE TRACKING
A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO.  THIS DANGEROUS
STORM WAS LOCATED 5 MILES EAST OF DOON...OR 9 MILES SOUTH OF ROCK
RAPIDS...MOVING EAST AT 20 MPH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR
OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.

&&

LAT...LON 4327 9612 4328 9615 4332 9617 4339 9608
      4328 9605
TIME...MOT...LOC 0116Z 260DEG 17KT 4330 9611

$$

CJ
220 
WWUS53 KFSD 020126
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
826 PM CDT TUE MAY 1 2012

IAC119-020136-
/O.EXP.KFSD.TO.W.0014.000000T0000Z-120502T0130Z/
LYON IA-
826 PM CDT TUE MAY 1 2012

...THE TORNADO WARNING FOR SOUTH CENTRAL LYON COUNTY WILL EXPIRE AT
830 PM CDT...

THE TORNADO THREAT HAS DIMINISHED...THEREFORE THE TORNADO WARNING HAS
EXPIRED. HOWEVER...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT 
FOR THE AREA.

LAT...LON 4327 9612 4328 9615 4332 9617 4339 9608
      4328 9605
TIME...MOT...LOC 0126Z 260DEG 17KT 4331 9605

$$

CJ

The office that day

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

IssuedProductOfficeCountiesLasted
May 1, 7:12 PM CDTSevere Thunderstorm WarningFSDLyon, Sioux33 min
May 1, 7:27 PM CDTTornado WarningFSDLyon, Sioux33 min
May 1, 7:41 PM CDTSevere Thunderstorm WarningFSDLyon, Sioux34 min
May 1, 8:09 PM CDTSevere Thunderstorm WarningFSDLyon36 min
May 1, 8:40 PM CDTFlash Flood WarningFSDLyon3 hr
May 1, 9:15 PM CDTSevere Thunderstorm WarningFSDBuena Vista, Cherokee, Clay, O'Brien, Plymouth, Sioux30 min
May 1, 9:22 PM CDTSevere Thunderstorm WarningFSDDickinson, Osceola38 min
May 1, 9:29 PM CDTTornado WarningFSDClay, O'Brien46 min
May 1, 9:41 PM CDTSevere Thunderstorm WarningFSDBuena Vista, Cherokee, Clay, Dickinson, O'Brien, Osceola34 min
May 1, 9:44 PM CDTTornado WarningFSDClay31 min
May 1, 10:13 PM CDTSevere Thunderstorm WarningFSDBuena Vista, Clay, Dickinson17 min

Nearby

Tornado Warnings in Iowa, 2012Every tornado warning in 2012Tornadoes in 2012

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.