Alert archive / Iowa / Tornado Warnings in 2011

Tornado Warning 20, NWS Des Moines, IA

April 9, 2011Sac County, Iowa

NWS Des Moines, IA issued this tornado warning at Apr 9, 2011, 8:41 PM CDT for Sac County, Iowa. It was in force for 34 min. 10 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Apr 9, 2011, 8:41 PM CDT (01:41 UTC)
Expired: Apr 9, 2011, 9:15 PM CDT
In force: 34 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon

County Sac County, IA

The radar

The Des Moines radar (KDMX), 138 km from the middle of the area, began a volume at 01:43 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	Remark
Apr 9, 8:41 PM CDT	HAIL 1.75	Wnw Early, IA
Apr 9, 8:43 PM CDT	TORNADO	2 Ne Odebolt, IA
Apr 9, 8:44 PM CDT	TORNADO	2 Sw Early, IA
Apr 9, 8:48 PM CDT	TSTM WND DMG	4 Se Schaller, IA	AROUND A DOZEN FOOT DIAMETER TREES DOWN AND/OR UPROOTED NEAR THE VICINITY OF HIGHWAY 20 AND COUNTY ROAD M43. MULTIPLE POWER POLES DOWN.
Apr 9, 8:48 PM CDT	TSTM WND DMG	Early, IA	MAJOR DAMAGE TO BUILDINGS IN TOWN. COMMERCIAL AND RESIDENTIAL. LARGE TREES DOWN. TIME ESTIMATED. NO INJURIES REPORTED IN EARLY AS OF YET.
Apr 9, 8:48 PM CDT	HAIL 1.25	Early, IA
Apr 9, 8:57 PM CDT	TORNADO	6 N Odebolt, IA	PUBLIC REPORTED A MORTON BUILDING DESTROYED.
Apr 9, 9:03 PM CDT	TORNADO	7 Nw Sac City, IA	TRAINED SPOTTER REPORTS LARGE WEDGE TORNADO ON THE GROUND.
Apr 9, 9:05 PM CDT	TSTM WND DMG	Nemaha, IA	MAJOR DAMAGE REPORTED IN NEMAHA...POSSIBLY FROM TORNADO. TIME APPROXIMATE.
Apr 9, 9:08 PM CDT	HAIL 2	3 W Nemaha, IA	WINDSHIELD BROKEN

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

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

Issued	Product	Office	Lasted
Apr 9, 5:48 PM CDT	Tornado Watch	SPC	7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 1.7 hours before the alert went out and 166 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: 3327 J/kg
Mixed-layer CIN: -24 J/kg
Mixed-layer LCL: 1533 m above ground
0-6 km bulk shear: 56 kt
0-1 km storm-relative helicity: 270 m²/s²
0-3 km storm-relative helicity: 403 m²/s²
Significant tornado parameter: 3.7
Supercell composite: 19.0

Open this sounding in Storm Lab

The text

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

041 
WFUS53 KDMX 100141
TORDMX
IAC161-100215-
/O.NEW.KDMX.TO.W.0020.110410T0141Z-110410T0215Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
841 PM CDT SAT APR 9 2011

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* TORNADO WARNING FOR...
  SAC COUNTY IN WEST CENTRAL IOWA...

* UNTIL 915 PM CDT

* AT 839 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO 7 MILES
  NORTHEAST OF ODEBOLT...OR 17 MILES SOUTH OF STORM LAKE. DOPPLER    
  RADAR SHOWED THIS TORNADO MOVING NORTHEAST AT 30 MPH. THIS WARNING 
  REPLACES THE PREVIOUS TORNADO WARNINGS FOR SAC COUNTY.

* LOCATIONS IMPACTED INCLUDE...
  SAC CITY...EARLY...NEMAHA AND LYTTON.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TO REPEAT...A TORNADO IS ON THE GROUND. THIS IS A DANGEROUS STORM.
IMMEDIATELY SEEK SHELTER IN A BASEMENT...OR IN AN INTERIOR ROOM OF A
REINFORCED BUILDING. STAY AWAY FROM WINDOWS.

IF YOU ARE OUTSIDE...IN A MOBILE HOME...OR IN A VEHICLE...SEEK
SHELTER IN A NEARBY REINFORCED BUILDING. AS A LAST RESORT...FIND THE
LOWEST SPOT AVAILABLE AND COVER YOUR HEAD.

&&

LAT...LON 4244 9533 4257 9503 4257 9493 4256 9492
      4248 9492 4247 9488 4238 9486 4227 9523
      4242 9534
TIME...MOT...LOC 0140Z 242DEG 26KT 4240 9517

$$

2 follow-up statements

870 
WWUS53 KDMX 100155
SVSDMX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
855 PM CDT SAT APR 9 2011

IAC161-100215-
/O.CON.KDMX.TO.W.0020.000000T0000Z-110410T0215Z/
SAC IA-
855 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR SAC COUNTY UNTIL 915 PM
CDT...

AT 852 PM CDT...THERE HAVE BEEN NUMEROUS REPORTS A TORNADO WITH THIS 
STORM.  THIS TORNADO WAS LOCATED 7 MILES WEST OF SAC CITY...OR 14 
MILES SOUTH OF STORM LAKE...MOVING NORTHEAST AT 25 MPH.

LOCATIONS IMPACTED INCLUDE...
  EARLY...SAC CITY AND NEMAHA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IMMEDIATELY SEEK SHELTER IN A BASEMENT...
OR IN AN INTERIOR ROOM OF A REINFORCED BUILDING. STAY AWAY FROM
WINDOWS.

IF YOU ARE OUTSIDE...IN A MOBILE HOME...OR IN A VEHICLE...SEEK
SHELTER IN A NEARBY REINFORCED BUILDING. AS A LAST RESORT...FIND THE
LOWEST SPOT AVAILABLE AND COVER YOUR HEAD.

&&

LAT...LON 4257 9503 4257 9493 4256 9492 4248 9492
      4247 9488 4238 9486 4227 9523 4241 9534
      4244 9533
TIME...MOT...LOC 0155Z 243DEG 23KT 4247 9509

$$

011 
WWUS53 KDMX 100206
SVSDMX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
906 PM CDT SAT APR 9 2011

IAC161-100215-
/O.CON.KDMX.TO.W.0020.000000T0000Z-110410T0215Z/
SAC IA-
906 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHERN SAC COUNTY UNTIL
915 PM CDT...

AT 905 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO.  THIS
TORNADO WAS LOCATED 7 MILES NORTHWEST OF SAC CITY...OR 11 MILES
SOUTHEAST OF STORM LAKE...MOVING EAST AT 30 MPH.

LOCATIONS IMPACTED INCLUDE...
  NEMAHA AND SAC CITY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IMMEDIATELY SEEK SHELTER IN A BASEMENT...
OR IN AN INTERIOR ROOM OF A REINFORCED BUILDING. STAY AWAY FROM
WINDOWS.

IF YOU ARE OUTSIDE...IN A MOBILE HOME...OR IN A VEHICLE...SEEK
SHELTER IN A NEARBY REINFORCED BUILDING. AS A LAST RESORT...FIND THE
LOWEST SPOT AVAILABLE AND COVER YOUR HEAD.

&&

LAT...LON 4257 9503 4257 9493 4256 9492 4248 9492
      4247 9488 4244 9487 4243 9488 4237 9531
      4240 9533 4244 9533
TIME...MOT...LOC 0207Z 252DEG 24KT 4251 9507

$$

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 9, 7:09 PM CDT	Tornado Warning	DMX	Crawford	51 min
Apr 9, 7:58 PM CDT	Tornado Warning	DMX	Sac	47 min
Apr 9, 8:23 PM CDT	Tornado Warning	DMX	Sac	22 min
Apr 9, 8:57 PM CDT	Severe Thunderstorm Warning	DMX	Kossuth, Palo Alto	33 min
Apr 9, 9:11 PM CDT	Tornado Warning	DMX	Calhoun, Pocahontas, Sac	49 min
Apr 9, 9:19 PM CDT	Severe Thunderstorm Warning	DMX	Sac	26 min
Apr 9, 9:48 PM CDT	Severe Thunderstorm Warning	DMX	Hancock, Kossuth, Winnebago	42 min
Apr 9, 9:55 PM CDT	Tornado Warning	DMX	Palo Alto, Pocahontas	35 min
Apr 9, 10:12 PM CDT	Tornado Warning	DMX	Hancock, Kossuth	33 min
Apr 9, 10:18 PM CDT	Tornado Warning	DMX	Cerro Gordo, Hancock, Winnebago, Worth	42 min
Apr 9, 10:22 PM CDT	Tornado Warning	DMX	Pocahontas	38 min
Apr 9, 10:28 PM CDT	Tornado Warning	DMX	Humboldt, Kossuth, Palo Alto, Pocahontas	47 min
Apr 9, 10:54 PM CDT	Tornado Warning	DMX	Humboldt, Kossuth, Palo Alto, Pocahontas	51 min
Apr 9, 10:58 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Worth	25 min
Apr 9, 11:11 PM CDT	Tornado Warning	DMX	Kossuth, Palo Alto	12 min
Apr 9, 11:24 PM CDT	Severe Thunderstorm Warning	DMX	Emmet, Kossuth, Palo Alto	36 min
Apr 9, 11:29 PM CDT	Tornado Warning	DMX	Hancock, Kossuth, Winnebago	33 min
Apr 9, 11:36 PM CDT	Tornado Warning	DMX	Emmet, Palo Alto	39 min
Apr 9, 11:41 PM CDT	Severe Thunderstorm Warning	DMX	Kossuth, Winnebago	49 min
Apr 9, 11:55 PM CDT	Tornado Warning	DMX	Kossuth, Palo Alto	35 min
Apr 9, 11:58 PM CDT	Severe Thunderstorm Warning	DMX	Winnebago, Worth	32 min
Apr 10, 12:24 AM CDT	Severe Thunderstorm Warning	DMX	Hancock, Kossuth, Winnebago, Worth	31 min
Apr 10, 12:53 AM CDT	Severe Thunderstorm Warning	DMX	Worth	22 min
Apr 10, 1:07 AM CDT	Severe Thunderstorm Warning	DMX	Sac	38 min
Apr 10, 1:38 AM CDT	Severe Thunderstorm Warning	DMX	Calhoun, Humboldt, Pocahontas, Webster	52 min
Apr 10, 3:54 AM CDT	Wind Advisory	DMX	Adair, Adams, Appanoose, Audubon, Black Hawk, Boone and 33 more	15 hr

Nearby

Tornado Warnings in Iowa, 2011 Every tornado warning in 2011 Tornadoes in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.