Alert archive / Iowa / Tornado Warnings in 2011

Tornado Warning 10, NWS Omaha, NE

April 9, 2011Monona County, Iowa

NWS Omaha, NE issued this tornado warning at Apr 9, 2011, 7:08 PM CDT for Monona County, Iowa. It was in force for 33 min. 3 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, 7:08 PM CDT (00:08 UTC)
Expired: Apr 9, 2011, 7:41 PM CDT
In force: 33 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon

County Monona County, IA

The radar

The Omaha radar (KOAX), 99 km from the middle of the area, began a volume at 00:11 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, 7:17 PM CDT	HAIL 1.75	2 S Mapleton, IA
Apr 9, 7:21 PM CDT	TORNADO	Mapleton, IA	TORNADO NEAR MAPLETON
Apr 9, 7:27 PM CDT	TORNADO	2 E Mapleton, 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.

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, 0.1 hours before the alert went out and 99 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.

032 
WFUS53 KOAX 100008
TOROAX
IAC133-100045-
/O.NEW.KOAX.TO.W.0010.110410T0008Z-110410T0045Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
708 PM CDT SAT APR 9 2011

THE NATIONAL WEATHER SERVICE IN OMAHA HAS ISSUED A

* TORNADO WARNING FOR...
  NORTHEASTERN MONONA COUNTY IN WEST CENTRAL IOWA...

* UNTIL 745 PM CDT

* AT 707 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
  SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS
  STORM WAS LOCATED 11 MILES EAST OF WHITING...OR 34 MILES SOUTHEAST
  OF SIOUX CITY...AND MOVING EAST AT 25 MPH.

* LOCATIONS IMPACTED INCLUDE...
  MAPLETON.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS TORNADO WARNING REPLACES THE SEVERE THUNDERSTORM WARNING THAT
WAS IN EFFECT FOR THE SAME AREA. GO TO A BASEMENT OR SMALL INTERIOR
ROOM ON THE LOWEST FLOOR!

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 4207 9585 4212 9600 4217 9599 4222 9567
      4207 9567
TIME...MOT...LOC 0008Z 268DEG 22KT 4214 9593

$$

NIETFELD

5 follow-up statements

199 
WWUS53 KOAX 100016
SVSOAX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
716 PM CDT SAT APR 9 2011

IAC133-100045-
/O.CON.KOAX.TO.W.0010.000000T0000Z-110410T0045Z/
MONONA IA-
716 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHEASTERN MONONA COUNTY
UNTIL 745 PM CDT...

AT 711 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO.  THIS
DANGEROUS STORM WAS LOCATED 10 MILES SOUTHWEST OF DANBURY...OR 35
MILES SOUTHEAST OF SIOUX CITY...MOVING EAST AT 30 MPH.

LOCATIONS IMPACTED INCLUDE...
  MAPLETON.

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 4212 9588 4215 9590 4218 9589 4222 9567
      4207 9567
TIME...MOT...LOC 0016Z 254DEG 27KT 4217 9584

$$

NIETFELD

979 
WWUS53 KOAX 100019
SVSOAX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
719 PM CDT SAT APR 9 2011

IAC133-100045-
/O.CON.KOAX.TO.W.0010.000000T0000Z-110410T0045Z/
MONONA IA-
719 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHEASTERN MONONA COUNTY
UNTIL 745 PM CDT...

AT 716 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO.  THIS
DANGEROUS STORM WAS LOCATED 7 MILES SOUTHWEST OF DANBURY...OR 38
MILES SOUTHEAST OF SIOUX CITY...MOVING EAST AT 40 MPH.

LOCATIONS IMPACTED INCLUDE...
  MAINLY RURAL AREAS OF NORTHEASTERN MONONA 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 4213 9584 4216 9585 4218 9586 4222 9567
      4207 9567
TIME...MOT...LOC 0020Z 260DEG 34KT 4217 9576

$$

NIETFELD

650 
WWUS53 KOAX 100025
SVSOAX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
725 PM CDT SAT APR 9 2011

IAC133-100045-
/O.CON.KOAX.TO.W.0010.000000T0000Z-110410T0045Z/
MONONA IA-
725 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHEASTERN MONONA COUNTY
UNTIL 745 PM CDT...

AT 721 PM CDT...EMERGENCY MANAGEMENT REPORTED A TORNADO.  THIS 
TORNADO WAS LOCATED NEAR MAPLETON...OR 38 MILES SOUTHEAST OF     
SIOUX CITY...MOVING EAST AT 40 MPH.

LOCATIONS IMPACTED INCLUDE...
  MAPLETON
  RURAL AREAS OF NORTHEASTERN MONONA COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TO REPEAT...A TORNADO IS ON THE GROUND. 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.

TO REPORT SEVERE WEATHER...CONTACT YOUR NEAREST LAW ENFORCEMENT
AGENCY. THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE
IN OMAHA.

&&

LAT...LON 4214 9582 4216 9582 4219 9580 4222 9567
      4207 9567
TIME...MOT...LOC 0024Z 259DEG 34KT 4217 9576

$$

NIETFELD

708 
WWUS53 KOAX 100029
SVSOAX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
729 PM CDT SAT APR 9 2011

IAC133-100045-
/O.CON.KOAX.TO.W.0010.000000T0000Z-110410T0045Z/
MONONA IA-
729 PM CDT SAT APR 9 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHEASTERN MONONA COUNTY
UNTIL 745 PM CDT...

AT 726 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS AND SPOTTERS
WERE TRACKING A LARGE AND EXTREMELY DANGEROUS TORNADO.  THIS TORNADO 
WAS LOCATED JUST EAST OF MAPLETON...OR 39 MILES SOUTHEAST OF SIOUX 
CITY...MOVING EAST AT 20 MPH.

LOCATIONS IMPACTED INCLUDE...
  
  MAINLY RURAL AREAS OF NORTHEASTERN MONONA COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINFALL MAY OBSCURE THIS TORNADO. DO NOT WAIT TO SEE OR HEAR 
THE TORNADO.  TORNADOES ARE DIFFICULT TO SEE AT NIGHT. TAKE COVER 
NOW.

&&

LAT...LON 4214 9580 4217 9580 4219 9578 4222 9567
      4207 9567
TIME...MOT...LOC 0028Z 259DEG 17KT 4217 9575

$$

NIETFELD

822 
WWUS53 KOAX 100041
SVSOAX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE OMAHA/VALLEY NEBRASKA
741 PM CDT SAT APR 9 2011

IAC133-100048-
/O.CAN.KOAX.TO.W.0010.000000T0000Z-110410T0045Z/
MONONA IA-
741 PM CDT SAT APR 9 2011

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

THE STORM WHICH PROMPTED THE TORNADO WARNING HAS MOVED OUT OF MONONA 
COUNTY.  

LAT...LON 4214 9580 4217 9580 4219 9578 4222 9567
      4207 9567
TIME...MOT...LOC 0038Z 248DEG 21KT 4220 9567

$$

NIETFELD

The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 10, 12:15 AM CDT	Severe Thunderstorm Warning	OAX	Monona	33 min
Apr 10, 3:52 AM CDT	Wind Advisory	OAX	Fremont, Harrison, Mills, Montgomery, Page, Pottawattamie and 1 more	11 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.