Alert archive / Iowa / Tornado Warnings in 2021

Tornado Warning 4, NWS Sioux Falls, SD

August 8, 2021Buena Vista County, Clay County, Iowa

NWS Sioux Falls, SD issued this tornado warning at Aug 8, 2021, 6:31 PM CDT for Buena Vista County, Clay County, Iowa. It was in force for 44 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: Aug 8, 2021, 6:31 PM CDT (23:31 UTC)
Expired: Aug 8, 2021, 7:15 PM CDT
In force: 44 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Tornado: Observed
Hail: 0.75 in

Counties Buena Vista County, IA, Clay County, IA

The radar

The Sioux Falls radar (KFSD), 148 km from the middle of the area, began a volume at 23:34 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 208 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: 1480 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 50 m²/s²
0-3 km storm-relative helicity: 109 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

961 
WFUS53 KFSD 082331
TORFSD
IAC021-041-090015-
/O.NEW.KFSD.TO.W.0004.210808T2331Z-210809T0015Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Sioux Falls SD
631 PM CDT Sun Aug 8 2021

The National Weather Service in Sioux Falls has issued a

* Tornado Warning for...
  Northeastern Buena Vista County in northwestern Iowa...
  Southern Clay County in northwestern Iowa...

* Until 715 PM CDT.

* At 630 PM CDT, a confirmed tornado was located near Greenville, or 
  3 miles south of Spencer In Clay County, moving southeast at 20 
  mph.

  HAZARD...Damaging tornado.

  SOURCE...Weather spotters 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.

* Locations impacted include...
  Sioux Rapids, Webb and Marathon.

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 4283 9524 4311 9538 4311 9507 4297 9491
      4283 9491
TIME...MOT...LOC 2330Z 327DEG 17KT 4302 9514 

TORNADO...OBSERVED
MAX HAIL SIZE...<.75 IN

$$

Kalin

1 follow-up statement

638 
WWUS53 KFSD 082342
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
642 PM CDT Sun Aug 8 2021

IAC021-041-090015-
/O.CON.KFSD.TO.W.0004.000000T0000Z-210809T0015Z/
Buena Vista IA-Clay IA-
642 PM CDT Sun Aug 8 2021

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 715 PM CDT FOR
NORTHEASTERN BUENA VISTA AND SOUTHERN CLAY COUNTIES...
    
At 641 PM CDT, a severe thunderstorm capable of producing a tornado
was located near Royal, or 8 miles southwest of Spencer In Clay
County, moving southeast at 15 mph.

HAZARD...Tornado.

SOURCE...Radar indicated rotation. A tornado was reported earlier 
         around 630 pm 3 miles south of Spencer. 

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...
Sioux Rapids, Royal, Marathon, Linn Grove, Webb, Greenville, Rossie
and Gillett Grove.

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 4283 9524 4309 9536 4309 9505 4297 9491
      4283 9491
TIME...MOT...LOC 2341Z 323DEG 13KT 4303 9522 

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

$$

Kalin

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 8, 4:10 PM CDT	Severe Thunderstorm Warning	FSD	Osceola	50 min
Aug 8, 4:29 PM CDT	Tornado Warning	FSD	Osceola	31 min
Aug 8, 4:50 PM CDT	Severe Thunderstorm Warning Considerable damage threat	FSD	Clay, Dickinson, O'Brien, Osceola	55 min
Aug 8, 5:26 PM CDT	Tornado Warning	FSD	Clay, Dickinson, O'Brien	49 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.