Alert archive / Iowa / Tornado Warnings in 2021

Tornado Warning 30, NWS Omaha, NE

December 15, 2021Shelby County, Iowa

NWS Omaha, NE issued this tornado warning at Dec 15, 2021, 4:55 PM CST for Shelby 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: Dec 15, 2021, 4:55 PM CST (22:55 UTC)
Expired: Dec 15, 2021, 5:09 PM CST
In force: 14 min
Issued by: NWS Omaha, NE
Area: Storm-based polygon
Tornado: Radar indicated
Hail: 0.75 in

County Shelby County, IA

The radar

The Omaha radar (KOAX), 98 km from the middle of the area, began a volume at 22:54 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 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, 10.9 hours before the alert went out and 98 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.

280 
WFUS53 KOAX 152255
TOROAX
IAC165-152330-
/O.NEW.KOAX.TO.W.0030.211215T2255Z-211215T2330Z/

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

The National Weather Service in Omaha has issued a

* Tornado Warning for...
  Northwestern Shelby County in southwestern Iowa...

* Until 530 PM CST.
    
* At 454 PM CST, a severe thunderstorm capable of producing a tornado
  was located near Earling, or 20 miles south of Denison, moving
  northeast at 75 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 dangerous storm will be near...
  Irwin around 500 PM CST.

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 4164 9537 4170 9550 4186 9539 4187 9538
      4186 9510
TIME...MOT...LOC 2254Z 212DEG 66KT 4173 9537 

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

$$

Kern

2 follow-up statements

033 
WWUS53 KOAX 152302 RRA
SVSOAX

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

IAC165-152330-
/O.CON.KOAX.TO.W.0030.000000T0000Z-211215T2330Z/
Shelby IA-
502 PM CST Wed Dec 15 2021

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 530 PM CST FOR NORTH
CENTRAL SHELBY COUNTY...
    
At 502 PM CST, a severe thunderstorm capable of producing a tornado
was located near Defiance, or 11 miles southeast of Denison, moving
northeast at 75 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
north central Shelby County.

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 4177 9521 4181 9539 4187 9538 4186 9510
TIME...MOT...LOC 2302Z 212DEG 66KT 4186 9526 

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

$$

Kern

323 
WWUS53 KOAX 152309 RRA
SVSOAX

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

IAC165-152319-
/O.CAN.KOAX.TO.W.0030.000000T0000Z-211215T2330Z/
Shelby IA-
509 PM CST Wed Dec 15 2021

...THE TORNADO WARNING FOR NORTH CENTRAL SHELBY COUNTY IS
CANCELLED...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning has been cancelled.  However gusty winds are
still possible with this thunderstorm.

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

LAT...LON 4177 9521 4181 9539 4187 9538 4186 9510
TIME...MOT...LOC 2308Z 212DEG 66KT 4198 9516 

$$

Kern

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, 4:30 PM CST	Tornado Warning	OAX	Mills, Montgomery, Pottawattamie	30 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

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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.