Alert archive / Iowa / Tornado Warnings in 2017

Tornado Warning 33, NWS Sioux Falls, SD

August 18, 2017Clay County, O'Brien County, Osceola County, Iowa

NWS Sioux Falls, SD issued this tornado warning at Aug 18, 2017, 8:25 PM CDT for Clay County, O'Brien County, Osceola County, Iowa. It was in force for 35 min. 6 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: Aug 18, 2017, 8:25 PM CDT (01:25 UTC)
Expired: Aug 18, 2017, 9:00 PM CDT
In force: 35 min
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Tornado: Observed
Damage threat: Considerable
Hail: 2.0 in

Counties Clay County, IA, O'Brien County, IA, Osceola County, IA

The radar

The Sioux Falls radar (KFSD), 103 km from the middle of the area, began a volume at 01:25 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.

What was reported inside it

Time	Report	Where	Remark
Aug 18, 8:30 PM CDT	HAIL 1.75	4 E Primghar, IA	BROADCAST MEDIA RELAY OF A PUBLIC REPORT.
Aug 18, 8:41 PM CDT	HAIL 1	2 W Hartley, IA
Aug 18, 8:44 PM CDT	HAIL 1.5	3 E Primghar, IA	TIME ESTIMATED FROM RADAR.
Aug 18, 8:44 PM CDT	HAIL 1.75	4 E Primghar, IA	HAIL FROM 830PM TO 845PM. TIME OF LARGEST HAIL ESTIMATED FROM RADAR.
Aug 18, 8:50 PM CDT	TSTM WND DMG	2 Nw Melvin, IA	FARMSTEAD DAMAGED. NO INJURIES.
Aug 18, 8:56 PM CDT	HAIL 1	4 N Sutherland, IA	TIME ESTIMATED FROM RADAR.

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
Aug 18, 4:51 PM CDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 1.4 hours before the alert went out and 222 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.

375 
WFUS53 KFSD 190125
TORFSD
IAC041-141-143-190200-
/O.NEW.KFSD.TO.W.0033.170819T0125Z-170819T0200Z/

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

The National Weather Service in Sioux Falls has issued a

* Tornado Warning for...
  Southeastern Osceola County in northwestern Iowa...
  West central Clay County in northwestern Iowa...
  Northeastern O'Brien County in northwestern Iowa...

* Until 900 PM CDT
    
* At 825 PM CDT, a confirmed large and extremely dangerous tornado
  was located over Melvin, or 11 miles southeast of Sibley, moving
  southeast at 25 mph.

  This is a PARTICULARLY DANGEROUS SITUATION. TAKE COVER NOW! 

  HAZARD...Damaging tornado. 

  SOURCE...Radar confirmed tornado. 

  IMPACT...You are in a life-threatening situation. Flying debris 
           may be deadly to those caught without shelter. Mobile 
           homes will be destroyed. Considerable damage to homes, 
           businesses, and vehicles is likely and complete 
           destruction is possible. 

* The tornado will be near...
  Hartley around 845 PM CDT. 

Other locations impacted by this tornadic thunderstorm include
Moneta.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To repeat, a large, extremely dangerous and potentially deadly
tornado is on the ground. To protect your life, 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.

Heavy rainfall may hide this tornado. Do not wait to see or hear the
tornado. TAKE COVER NOW!

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

&&

LAT...LON 4332 9570 4338 9554 4308 9528 4301 9556
TIME...MOT...LOC 0125Z 328DEG 20KT 4328 9561 

TORNADO...OBSERVED
TORNADO DAMAGE THREAT...CONSIDERABLE
HAIL...2.00IN

$$

Ferguson

1 follow-up statement

338 
WWUS53 KFSD 190139
SVSFSD

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

IAC143-190149-
/O.CAN.KFSD.TO.W.0033.000000T0000Z-170819T0200Z/
Osceola IA-
839 PM CDT FRI AUG 18 2017

...THE TORNADO WARNING FOR SOUTHEASTERN OSCEOLA 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 4301 9556 4326 9567 4325 9543 4308 9528
TIME...MOT...LOC 0139Z 328DEG 20KT 4321 9555 

$$

IAC041-141-190200-
/O.CON.KFSD.TO.W.0033.000000T0000Z-170819T0200Z/
Clay IA-O'Brien IA-
839 PM CDT FRI AUG 18 2017

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 900 PM CDT FOR WEST
CENTRAL CLAY AND NORTHEASTERN O'BRIEN COUNTIES...
    
At 839 PM CDT, a severe thunderstorm capable of producing a tornado
was located near Hartley, or 14 miles east of Sheldon, moving
southeast at 25 mph.

HAZARD...Tornado and two inch 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...
  Hartley around 850 PM CDT. 

Other locations impacted by this tornadic thunderstorm include
Moneta.

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.

Heavy rainfall may hide this tornado. Do not wait to see or hear the
tornado. TAKE COVER NOW!

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

&&

LAT...LON 4301 9556 4326 9567 4325 9543 4308 9528
TIME...MOT...LOC 0139Z 328DEG 20KT 4321 9555 

TORNADO...RADAR INDICATED
HAIL...2.00IN

$$

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, 8:37 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, 9:26 PM CDT	Tornado Warning	FSD	Buena Vista, Cherokee, O'Brien	34 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.