Alert archive / Iowa / Tornado Warnings in 2012

Tornado Warning 11, NWS Sioux Falls, SD

April 21, 2012Clay County, Iowa

NWS Sioux Falls, SD issued this tornado warning at Apr 21, 2012, 4:45 PM CDT for Clay County, Iowa. It was in force for 14 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: Apr 21, 2012, 4:45 PM CDT (21:45 UTC)
Expired: Apr 21, 2012, 4:59 PM CDT
In force: 14 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon

County Clay County, IA

The radar

The Sioux Falls radar (KFSD), 153 km from the middle of the area, began a volume at 21:47 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

Omaha, NE (KOAX), launched 12:00Z, 9.8 hours before the alert went out and 222 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: 1613 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 110 m²/s²
0-3 km storm-relative helicity: 269 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.

784 
WFUS53 KFSD 212145
TORFSD
IAC041-212215-
/O.NEW.KFSD.TO.W.0011.120421T2145Z-120421T2215Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
445 PM CDT SAT APR 21 2012

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* TORNADO WARNING FOR...
  SOUTHEASTERN CLAY COUNTY IN NORTHWEST IOWA...

* UNTIL 515 PM CDT

* AT 444 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS WERE   
TRACKING A CONFIRMED TORNADO 10 MILES SOUTH SOUTHEAST OF 
DICKENS...OR 12 MILES SOUTHEAST OF SPENCER. DOPPLER RADAR SHOWED 
THIS TORNADO MOVING SOUTHEAST AT 30 MPH.

* THE TORNADO WILL AFFECT MAINLY RURAL AREAS OF SOUTHEASTERN CLAY
  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 4304 9511 4317 9501 4313 9490 4293 9491
      4292 9491
TIME...MOT...LOC 2144Z 300DEG 25KT 4305 9498

$$

HANKO

1 follow-up statement

069 
WWUS53 KFSD 212159
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
459 PM CDT SAT APR 21 2012

IAC041-212210-
/O.CAN.KFSD.TO.W.0011.000000T0000Z-120421T2215Z/
CLAY IA-
459 PM CDT SAT APR 21 2012

...THE TORNADO WARNING FOR SOUTHEASTERN CLAY COUNTY IS CANCELLED...

THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED AND MOVED OUT OF
THE WARNED AREA.

LAT...LON 4304 9511 4317 9501 4313 9490 4293 9491
      4292 9491
TIME...MOT...LOC 2200Z 300DEG 25KT 4299 9485

$$

HANKO

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 21, 4:21 PM CDT	Tornado Warning	FSD	Clay	24 min
Apr 21, 4:38 PM CDT	Tornado Warning	FSD	Dickinson	37 min

Nearby

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