Alert archive / Iowa / Tornado Warnings in 2020

Tornado Warning 7, NWS Des Moines, IA

May 25, 2020Polk County, Iowa

NWS Des Moines, IA issued this tornado warning at May 25, 2020, 6:32 PM CDT for Polk County, Iowa. It was in force for 28 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: May 25, 2020, 6:32 PM CDT (23:32 UTC)
Expired: May 25, 2020, 7:00 PM CDT
In force: 28 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Tornado: Observed
Hail: 0.75 in

County Polk County, IA

The radar

The Des Moines radar (KDMX), 8 km from the middle of the area, began a volume at 23:31 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 nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.5 hours before the alert went out and 233 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: 83 J/kg
Mixed-layer CIN: -111 J/kg
Mixed-layer LCL: 758 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 53 m²/s²
0-3 km storm-relative helicity: 256 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

538 
WFUS53 KDMX 252332
TORDMX
IAC153-260000-
/O.NEW.KDMX.TO.W.0007.200525T2332Z-200526T0000Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Des Moines IA
632 PM CDT Mon May 25 2020

The National Weather Service in Des Moines  has issued a

* Tornado Warning for...
  Northwestern Polk County in central Iowa...

* Until 700 PM CDT.
    
* At 631 PM CDT, a tornado producing storm was located over Johnston,
  moving northeast at 30 mph.

  HAZARD...Damaging tornado.

  SOURCE...Radar confirmed tornado.

  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 storm will be near...
  Ankeny around 635 PM CDT.
  Polk City around 640 PM CDT.

Other locations impacted by this tornadic thunderstorm include
Elkhart and Alleman.

This includes Interstate 35 between mile markers 92 and 100.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

To repeat, a tornado is on the ground. 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 4165 9369 4167 9373 4186 9362 4186 9359
      4176 9346
TIME...MOT...LOC 2331Z 218DEG 25KT 4170 9367 

TORNADO...OBSERVED
HAIL...<.75IN

$$

Krull

3 follow-up statements

443 
WWUS53 KDMX 252340
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
640 PM CDT Mon May 25 2020

IAC153-260000-
/O.CON.KDMX.TO.W.0007.000000T0000Z-200526T0000Z/
Polk IA-
640 PM CDT Mon May 25 2020

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 700 PM CDT FOR NORTH
CENTRAL POLK COUNTY...
        
At 640 PM CDT, a confirmed tornado was located near Ankeny, moving
northeast at 40 mph.

HAZARD...Damaging tornado.

SOURCE...Radar confirmed tornado.

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 Polk County, including the following locations...
Alleman.

This includes Interstate 35 between mile markers 97 and 100.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

To repeat, a tornado is on the ground. 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 4171 9364 4173 9369 4186 9362 4186 9359
      4181 9353
TIME...MOT...LOC 2340Z 203DEG 33KT 4177 9363 

TORNADO...OBSERVED
HAIL...<.75IN

$$

Krull

900 
WWUS53 KDMX 252348
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
648 PM CDT Mon May 25 2020

IAC153-260000-
/O.CON.KDMX.TO.W.0007.000000T0000Z-200526T0000Z/
Polk IA-
648 PM CDT Mon May 25 2020

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 700 PM CDT FOR NORTH
CENTRAL POLK COUNTY...
    
At 648 PM CDT, a severe thunderstorm capable of producing a tornado
was located near Ankeny, moving northeast at 30 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...
Ankeny and Alleman. 

This includes Interstate 35 between mile markers 97 and 100.
 
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 4176 9359 4179 9365 4186 9362 4186 9359
      4181 9353
TIME...MOT...LOC 2348Z 218DEG 25KT 4181 9358 

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

$$

Krull

727 
WWUS53 KDMX 252352
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
652 PM CDT Mon May 25 2020

IAC153-260002-
/O.EXP.KDMX.TO.W.0007.000000T0000Z-200526T0000Z/
Polk IA-
652 PM CDT Mon May 25 2020

...THE TORNADO WARNING FOR NORTH CENTRAL POLK COUNTY WILL EXPIRE AT
700 PM CDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer appears capable of producing a tornado.
Therefore, the warning will be allowed to expire.  However gusty
winds are still possible with this thunderstorm.

LAT...LON 4176 9359 4179 9365 4186 9362 4186 9359
      4181 9353
TIME...MOT...LOC 2352Z 218DEG 25KT 4182 9357 

$$

Krull

The office that day

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

Issued	Product	Office	Counties	Lasted
May 24, 8:18 PM CDT	Special Weather Statement	DMX	Madison	57 min
May 25, 5:24 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marshall	37 min
May 25, 5:31 PM CDT	Severe Thunderstorm Warning	DMX	Clarke, Decatur, Lucas, Wayne	44 min
May 25, 6:44 PM CDT	Severe Thunderstorm Warning	DMX	Franklin, Hamilton, Hardin, Wright	31 min

Nearby

Tornado Warnings in Iowa, 2020 Every tornado warning in 2020 Tornadoes in 2020

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.