Alert archive / Iowa / Tornado Warnings in 2021

Tornado Warning 25, NWS Omaha, NE

December 15, 2021Mills County, Montgomery County, Pottawattamie County, Iowa

NWS Omaha, NE issued this tornado warning at Dec 15, 2021, 4:30 PM CST for Mills County, Montgomery County, Pottawattamie County, Iowa. It was in force for 30 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: Dec 15, 2021, 4:30 PM CST (22:30 UTC)
Expired: Dec 15, 2021, 5:00 PM CST
In force: 30 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Tornado: Radar indicated
Hail: 0.75 in

Counties Mills County, IA, Montgomery County, IA, Pottawattamie County, IA

The radar

The Omaha radar (KOAX), 83 km from the middle of the area, began a volume at 22:29 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
Dec 15, 4:31 PM CST	TORNADO	4 S Henderson, IA	A SHORT-LIVED TORNADO DEVELOPED ON A FARM WHERE IT QUICKLY DESTROYED A METAL BUILDING STRUCTURE, FLIPPING TWO TRUCKS THAT WERE PARKED INSIDE THE BUILDING. THE ROOF WAS FLIPPED OFF OF THE STRUCTURE AND DEBRIS WAS DISTRIBUTED TO THE NORTHEAST. THE TORNADO THEN I
Dec 15, 4:34 PM CST	TORNADO	3 E Macedonia, IA	A TORNADO TRACKED FROM EAST OF MACEDONIA TO EAST OF OAKLAND, CROSSING APPROXIMATELY 9.5 MILES IN APPROXIMATELY 8 MINUTES WITH A MAXIMUM WIDTH OF APPROXIMATELY 50 YARDS. THE TORNADO CAUSED INTERMITTENT DAMAGE TO TREES, OUTBUILDINGS, AND HOMES ALONG THE TRACK.
Dec 15, 4:40 PM CST	TSTM WND DMG	5 Ese Carson, IA	MACHINE SHED DESTROYED.
Dec 15, 5:00 PM CST	TSTM WND DMG	1 Nw Treynor, IA	POWERLINES DOWN.

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
Dec 15, 1:23 PM CST	Tornado Watch	SPC	7 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.5 hours before the alert went out and 83 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: 2165 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 346 m²/s²
0-3 km storm-relative helicity: 384 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

286 
WFUS53 KOAX 152230
TOROAX
IAC129-137-155-152300-
/O.NEW.KOAX.TO.W.0025.211215T2230Z-211215T2300Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Omaha/Valley Nebraska
430 PM CST Wed Dec 15 2021

The National Weather Service in Omaha has issued a

* Tornado Warning for...
  Northwestern Montgomery County in southwestern Iowa...
  Northeastern Mills County in southwestern Iowa...
  Southeastern Pottawattamie County in southwestern Iowa...

* Until 500 PM CST.
    
* At 430 PM CST, a severe thunderstorm capable of producing a tornado
  was located near Emerson, or 31 miles southwest of Atlantic, moving
  northeast at 80 mph.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Flying debris will be dangerous to those caught without 
           shelter. Mobile homes will be damaged or destroyed. 
           Damage to roofs, windows, and vehicles will occur.  Tree 
           damage is likely.

* This tornadic thunderstorm will remain over mainly rural areas of
  northwestern Montgomery, northeastern Mills and southeastern
  Pottawattamie Counties, including the following locations... Old
  Town Park, Hastings, Silver City, Farm Creek Public Wildlife Area
  and Henderson.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 4096 9545 4116 9572 4140 9546 4134 9515
      4116 9516
TIME...MOT...LOC 2230Z 228DEG 69KT 4107 9544 

TORNADO...RADAR INDICATED
MAX HAIL SIZE...<.75 IN

$$

CA

2 follow-up statements

230 
WWUS53 KOAX 152242
SVSOAX

Severe Weather Statement
National Weather Service Omaha/Valley Nebraska
442 PM CST Wed Dec 15 2021

IAC129-137-152252-
/O.CAN.KOAX.TO.W.0025.000000T0000Z-211215T2300Z/
Montgomery IA-Mills IA-
442 PM CST Wed Dec 15 2021

...THE TORNADO WARNING FOR NORTHWESTERN MONTGOMERY AND NORTHEASTERN
MILLS COUNTIES IS CANCELLED...
    
The tornadic thunderstorm which prompted the warning has moved out 
of the warned area. Therefore, the warning has been cancelled.

A Tornado Watch remains in effect until 800 PM CST for southwestern
Iowa.

LAT...LON 4117 9516 4116 9516 4116 9519 4123 9539
      4140 9546 4134 9515
TIME...MOT...LOC 2242Z 222DEG 69KT 4127 9525 

$$

IAC155-152300-
/O.CON.KOAX.TO.W.0025.000000T0000Z-211215T2300Z/
Pottawattamie IA-
442 PM CST Wed Dec 15 2021

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 500 PM CST FOR
SOUTHEASTERN POTTAWATTAMIE COUNTY...
    
At 442 PM CST, a severe thunderstorm capable of producing a tornado
was located 6 miles northwest of Griswold, or 15 miles southwest of
Atlantic, moving northeast at 80 mph.

HAZARD...Tornado.

SOURCE...Radar indicated rotation.

IMPACT...Flying debris will be dangerous to those caught without 
         shelter. Mobile homes will be damaged or destroyed. Damage 
         to roofs, windows, and vehicles will occur.  Tree damage is 
         likely.

Locations impacted include...
Oakland and Farm Creek Public Wildlife Area. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 4117 9516 4116 9516 4116 9519 4123 9539
      4140 9546 4134 9515
TIME...MOT...LOC 2242Z 222DEG 69KT 4127 9525 

TORNADO...RADAR INDICATED
MAX HAIL SIZE...<.75 IN

$$

CA

610 
WWUS53 KOAX 152257
SVSOAX

Severe Weather Statement
National Weather Service Omaha/Valley Nebraska
457 PM CST Wed Dec 15 2021

IAC155-152306-
/O.EXP.KOAX.TO.W.0025.000000T0000Z-211215T2300Z/
Pottawattamie IA-
457 PM CST Wed Dec 15 2021

...THE TORNADO WARNING FOR SOUTHEASTERN POTTAWATTAMIE COUNTY WILL
EXPIRE AT 500 PM CST...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning will be allowed to expire.

A Tornado Watch remains in effect until 800 PM CST for southwestern
Iowa.

LAT...LON 4117 9516 4116 9516 4116 9519 4123 9539
      4140 9546 4134 9515
TIME...MOT...LOC 2256Z 228DEG 69KT 4145 9498 

$$

CA

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 15, 3:35 PM CST	Severe Thunderstorm Warning Destructive damage threat	OAX	Fremont, Harrison, Mills, Pottawattamie	70 min
Dec 15, 3:41 PM CST	Severe Thunderstorm Warning Destructive damage threat	OAX	Harrison, Monona	64 min
Dec 15, 3:55 PM CST	Severe Thunderstorm Warning Destructive damage threat	OAX	Fremont, Harrison, Mills, Montgomery, Page, Pottawattamie and 1 more	80 min
Dec 15, 4:01 PM CST	Tornado Warning	OAX	Fremont, Mills	14 min
Dec 15, 4:12 PM CST	Tornado Warning	OAX	Fremont, Mills	33 min
Dec 15, 4:16 PM CST	Tornado Warning	OAX	Harrison, Pottawattamie	17 min
Dec 15, 4:21 PM CST	Tornado Warning	OAX	Pottawattamie	24 min
Dec 15, 4:31 PM CST	Tornado Warning	OAX	Harrison, Monona, Shelby	13 min
Dec 15, 4:37 PM CST	Tornado Warning Tornado observed	OAX	Harrison, Shelby	23 min
Dec 15, 4:46 PM CST	Tornado Warning	OAX	Pottawattamie, Shelby	20 min
Dec 15, 4:54 PM CST	Tornado Warning	OAX	Montgomery, Page	15 min
Dec 15, 4:55 PM CST	Tornado Warning	OAX	Shelby	14 min

Nearby

Tornado Warnings in Iowa, 2021 Every tornado warning in 2021 Tornadoes in 2021

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.