Alert archive / Iowa / Tornado Warnings in 2017

Tornado Warning 36, NWS Sioux Falls, SD

August 18, 2017Buena Vista County, Cherokee County, O'Brien County, Iowa

NWS Sioux Falls, SD issued this tornado warning at Aug 18, 2017, 9:26 PM CDT for Buena Vista County, Cherokee County, O'Brien County, Iowa. It was in force for 34 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 18, 2017, 9:26 PM CDT (02:26 UTC)
Expired: Aug 18, 2017, 10:00 PM CDT
In force: 34 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Tornado: Radar indicated
Hail: 1.5 in

Counties Buena Vista County, IA, Cherokee County, IA, O'Brien County, IA

The radar

The Sioux Falls radar (KFSD), 146 km from the middle of the area, began a volume at 02:25 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
Aug 18, 4:51 PM CDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.4 hours before the alert went out and 180 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: 1353 J/kg
Mixed-layer CIN: -118 J/kg
Mixed-layer LCL: 1673 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 30 m²/s²
0-3 km storm-relative helicity: 61 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

Open this sounding in Storm Lab

The text

As transmitted.

936 
WFUS53 KFSD 190226
TORFSD
IAC021-035-141-190300-
/O.NEW.KFSD.TO.W.0036.170819T0226Z-170819T0300Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Sioux Falls SD
926 PM CDT FRI AUG 18 2017

The National Weather Service in Sioux Falls has issued a

* Tornado Warning for...
  Eastern Cherokee County in northwestern Iowa...
  Southwestern Buena Vista County in northwestern Iowa...
  Southeastern O'Brien County in northwestern Iowa...

* Until 1000 PM CDT
    
* At 926 PM CDT, a severe thunderstorm capable of producing a tornado
  was located near Larrabee, or 7 miles northeast of Cherokee, moving
  southeast at 30 mph.

  HAZARD...Tornado and ping pong ball size hail. 

  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...
  Aurelia around 940 PM CDT. 
  Alta around 955 PM CDT. 

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.

Tornadoes are extremely difficult to see and confirm at night. Do not
wait to see or hear the tornado. TAKE COVER NOW!

&&

LAT...LON 4269 9515 4258 9544 4284 9555 4295 9543
TIME...MOT...LOC 0226Z 322DEG 25KT 4283 9545 

TORNADO...RADAR INDICATED
HAIL...1.50IN

$$

Ferguson

2 follow-up statements

137 
WWUS53 KFSD 190239
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
939 PM CDT FRI AUG 18 2017

IAC141-190248-
/O.CAN.KFSD.TO.W.0036.000000T0000Z-170819T0300Z/
O'Brien IA-
939 PM CDT FRI AUG 18 2017

...THE TORNADO WARNING FOR SOUTHEASTERN O'BRIEN COUNTY IS
CANCELLED...
    
The tornadic thunderstorm which prompted the warning has moved out 
of the warned area therefore, the warning has been cancelled.

A severe thunderstorm watch remains in effect until 100 AM CDT for
northwestern Iowa.

LAT...LON 4269 9515 4258 9544 4279 9553 4287 9537
TIME...MOT...LOC 0238Z 326DEG 29KT 4277 9542 

$$

IAC021-035-190300-
/O.CON.KFSD.TO.W.0036.000000T0000Z-170819T0300Z/
Cherokee IA-Buena Vista IA-
939 PM CDT FRI AUG 18 2017

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 1000 PM CDT FOR
SOUTHEASTERN CHEROKEE AND SOUTHWESTERN BUENA VISTA COUNTIES...
    
At 938 PM CDT, a severe thunderstorm capable of producing a tornado
was located near Aurelia, or near Cherokee, moving southeast at 35
mph.

HAZARD...Tornado and ping pong ball size hail. 

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...
  Alta around 955 PM CDT. 

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.

Tornadoes are extremely difficult to see and confirm at night. Do not
wait to see or hear the tornado. TAKE COVER NOW!

&&

LAT...LON 4269 9515 4258 9544 4279 9553 4287 9537
TIME...MOT...LOC 0238Z 326DEG 29KT 4277 9542 

TORNADO...RADAR INDICATED
HAIL...1.50IN

$$

Ferguson

162 
WWUS53 KFSD 190257
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
957 PM CDT FRI AUG 18 2017

IAC021-035-190307-
/O.EXP.KFSD.TO.W.0036.000000T0000Z-170819T0300Z/
Cherokee IA-Buena Vista IA-
957 PM CDT FRI AUG 18 2017

...THE TORNADO WARNING FOR SOUTHEASTERN CHEROKEE AND SOUTHWESTERN
BUENA VISTA COUNTIES WILL EXPIRE AT 1000 PM CDT...
    
The tornado threat has diminished and the Tornado Warning has been
cancelled. However, large hail and damaging winds remain likely and a
Severe Thunderstorm Warning remains in effect for the area.

A severe thunderstorm watch remains in effect until 100 AM CDT for
northwestern Iowa.

To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
Sioux Falls.

LAT...LON 4269 9515 4258 9544 4279 9553 4287 9537
TIME...MOT...LOC 0257Z 322DEG 25KT 4267 9531 

$$

Ferguson

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 7:45 PM CDT	Severe Thunderstorm Warning	FSD	Osceola	30 min
Aug 18, 7:49 PM CDT	Tornado Warning	FSD	Osceola	26 min
Aug 18, 8:06 PM CDT	Tornado Warning	FSD	Clay, O'Brien, Osceola	24 min
Aug 18, 8:25 PM CDT	Tornado Warning Tornado observedConsiderable damage threat	FSD	Clay, O'Brien, Osceola	35 min
Aug 18, 8:37 PM CDT	Tornado Warning	FSD	Clay, O'Brien	23 min
Aug 18, 8:54 PM CDT	Tornado Warning	FSD	Buena Vista, Cherokee, Clay, O'Brien	36 min
Aug 18, 9:53 PM CDT	Severe Thunderstorm Warning	FSD	Buena Vista, Cherokee, Ida	37 min

Nearby

Tornado Warnings in Iowa, 2017 Every tornado warning in 2017 Tornadoes in 2017

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.