Alert archive / Iowa / Tornado Warnings in 2011

Tornado Warning 21, NWS Des Moines, IA

April 9, 2011Calhoun County, Pocahontas County, Sac County, Iowa

NWS Des Moines, IA issued this tornado warning at Apr 9, 2011, 9:11 PM CDT for Calhoun County, Pocahontas County, Sac County, Iowa. It was in force for 49 min. 4 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, 9:11 PM CDT (02:11 UTC)
Expired
Apr 9, 2011, 10:00 PM CDT
In force
49 min
Issued by
NWS Des Moines, IA
Area
Storm-based polygon

Counties Calhoun County, IA, Pocahontas County, IA, Sac County, IA

The radar

The Des Moines radar (KDMX), 135 km from the middle of the area, began a volume at 02:13 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

TimeReportWhereRemark
Apr 9, 9:30 PM CDTTSTM WND DMG5 Ene Nemaha, IAPOWER LINES DOWN...HOUSE DAMAGED. GAS LEAKING. LIKELY TORNADO DAMAGE.
Apr 9, 9:52 PM CDTTORNADO2 N Fonda, IA
Apr 9, 9:55 PM CDTTORNADOVarina, IALOCATION APPROXIMATE. NEAR VARINA TOWARD THE POCAHONTAS/BUENA VISTA COUNTY LINE.
Apr 9, 10:09 PM CDTHAIL 1.51 Nw Pocahontas, IA

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.

IssuedProductOfficeLasted
Apr 9, 5:48 PM CDTTornado WatchSPC7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.2 hours before the alert went out and 186 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 2011-04-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 3327 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 2011-04-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 270 square meters per square second.19395878Sfc1 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
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.

971 
WFUS53 KDMX 100211
TORDMX
IAC025-151-161-100300-
/O.NEW.KDMX.TO.W.0021.110410T0211Z-110410T0300Z/

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

THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A

* TORNADO WARNING FOR...
  NORTHWESTERN CALHOUN COUNTY IN WEST CENTRAL IOWA...
  SOUTHERN POCAHONTAS COUNTY IN NORTHWEST IOWA...
  NORTHEASTERN SAC COUNTY IN WEST CENTRAL IOWA...

* UNTIL 1000 PM CDT

* AT 909 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS
  STORM WAS LOCATED 7 MILES NORTH OF SAC CITY...OR 12 MILES SOUTHEAST
  OF STORM LAKE...AND MOVING EAST AT 25 MPH. THIS STORM HAS A        
  HISTORY OF PRODUCING TORNADOES.

* LOCATIONS IMPACTED INCLUDE...
  POCAHONTAS...MANSON...VARINA...FONDA...POMEROY AND PALMER.

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 9506 4257 9492 4268 9493 4274 9492
      4280 9463 4253 9450 4245 9486 4247 9486
      4247 9499 4256 9507
TIME...MOT...LOC 0211Z 250DEG 21KT 4252 9503

$$
2 follow-up statements
239 
WWUS53 KDMX 100235
SVSDMX

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

IAC161-100245-
/O.CAN.KDMX.TO.W.0021.000000T0000Z-110410T0300Z/
SAC IA-
935 PM CDT SAT APR 9 2011

...THE TORNADO WARNING FOR NORTHEASTERN SAC COUNTY IS CANCELLED...

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

LAT...LON 4269 9492 4274 9492 4280 9463 4253 9450
      4245 9486 4248 9486 4248 9492 4267 9493
      4269 9493
TIME...MOT...LOC 0235Z 250DEG 21KT 4257 9485

$$

IAC025-151-100300-
/O.CON.KDMX.TO.W.0021.000000T0000Z-110410T0300Z/
POCAHONTAS IA-CALHOUN IA-
935 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHWESTERN CALHOUN AND
SOUTHERN POCAHONTAS COUNTIES UNTIL 1000 PM CDT...

AT 934 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO.  THIS
TORNADO WAS LOCATED 8 MILES SOUTHEAST OF NEWELL...OR 18 MILES EAST OF
STORM LAKE...MOVING EAST AT 25 MPH. THIS STORM HAS A HISTORY OF 
DAMAGE.

LOCATIONS IMPACTED INCLUDE...
  POCAHONTAS...MANSON...FONDA...POMEROY AND PALMER.

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 4269 9492 4274 9492 4280 9463 4253 9450
      4245 9486 4248 9486 4248 9492 4267 9493
      4269 9493
TIME...MOT...LOC 0235Z 250DEG 21KT 4257 9485

$$
153 
WWUS53 KDMX 100246
SVSDMX

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

IAC025-100256-
/O.CAN.KDMX.TO.W.0021.000000T0000Z-110410T0300Z/
CALHOUN IA-
946 PM CDT SAT APR 9 2011

...THE TORNADO WARNING FOR NORTHWESTERN CALHOUN COUNTY IS
CANCELLED...

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

LAT...LON 4269 9492 4274 9492 4280 9463 4258 9452
      4256 9479 4256 9491 4267 9493 4269 9493
TIME...MOT...LOC 0246Z 241DEG 24KT 4263 9480

$$

IAC151-100300-
/O.CON.KDMX.TO.W.0021.000000T0000Z-110410T0300Z/
POCAHONTAS IA-
946 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR SOUTHERN POCAHONTAS COUNTY
UNTIL 1000 PM CDT...

AT 943 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO.  THIS
TORNADO WAS LOCATED 9 MILES EAST OF NEWELL...OR 19 MILES EAST OF
STORM LAKE...MOVING NORTHEAST AT 25 MPH.

LOCATIONS IMPACTED INCLUDE...
  POCAHONTAS AND PALMER.

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 4269 9492 4274 9492 4280 9463 4258 9452
      4256 9479 4256 9491 4267 9493 4269 9493
TIME...MOT...LOC 0246Z 241DEG 24KT 4263 9480

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 9, 7:09 PM CDTTornado WarningDMXCrawford51 min
Apr 9, 7:58 PM CDTTornado WarningDMXSac47 min
Apr 9, 8:23 PM CDTTornado WarningDMXSac22 min
Apr 9, 8:41 PM CDTTornado WarningDMXSac34 min
Apr 9, 8:57 PM CDTSevere Thunderstorm WarningDMXKossuth, Palo Alto33 min
Apr 9, 9:19 PM CDTSevere Thunderstorm WarningDMXSac26 min
Apr 9, 9:48 PM CDTSevere Thunderstorm WarningDMXHancock, Kossuth, Winnebago42 min
Apr 9, 9:55 PM CDTTornado WarningDMXPalo Alto, Pocahontas35 min
Apr 9, 10:12 PM CDTTornado WarningDMXHancock, Kossuth33 min
Apr 9, 10:18 PM CDTTornado WarningDMXCerro Gordo, Hancock, Winnebago, Worth42 min
Apr 9, 10:22 PM CDTTornado WarningDMXPocahontas38 min
Apr 9, 10:28 PM CDTTornado WarningDMXHumboldt, Kossuth, Palo Alto, Pocahontas47 min
Apr 9, 10:54 PM CDTTornado WarningDMXHumboldt, Kossuth, Palo Alto, Pocahontas51 min
Apr 9, 10:58 PM CDTSevere Thunderstorm WarningDMXCerro Gordo, Worth25 min
Apr 9, 11:11 PM CDTTornado WarningDMXKossuth, Palo Alto12 min
Apr 9, 11:24 PM CDTSevere Thunderstorm WarningDMXEmmet, Kossuth, Palo Alto36 min
Apr 9, 11:29 PM CDTTornado WarningDMXHancock, Kossuth, Winnebago33 min
Apr 9, 11:36 PM CDTTornado WarningDMXEmmet, Palo Alto39 min
Apr 9, 11:41 PM CDTSevere Thunderstorm WarningDMXKossuth, Winnebago49 min
Apr 9, 11:55 PM CDTTornado WarningDMXKossuth, Palo Alto35 min
Apr 9, 11:58 PM CDTSevere Thunderstorm WarningDMXWinnebago, Worth32 min
Apr 10, 12:24 AM CDTSevere Thunderstorm WarningDMXHancock, Kossuth, Winnebago, Worth31 min
Apr 10, 12:53 AM CDTSevere Thunderstorm WarningDMXWorth22 min
Apr 10, 1:07 AM CDTSevere Thunderstorm WarningDMXSac38 min
Apr 10, 1:38 AM CDTSevere Thunderstorm WarningDMXCalhoun, Humboldt, Pocahontas, Webster52 min
Apr 10, 3:54 AM CDTWind AdvisoryDMXAdair, Adams, Appanoose, Audubon, Black Hawk, Boone and 33 more15 hr

Nearby

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