Alert archive / South Dakota / Tornado Watches in 2014

Tornado Watch 474

August 23, 20148 counties in South Dakota

The Storm Prediction Center issued this tornado watch at Aug 23, 2014, 6:15 PM CDT for 8 counties in South Dakota. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued: Aug 23, 2014, 6:15 PM CDT (23:15 UTC)
Expired: Aug 23, 2014, 10:00 PM CDT
In force: 4 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

Counties Brown County, SD, Clark County, SD, Day County, SD, Edmunds County, SD, Faulk County, SD, Marshall County, SD, McPherson County, SD, Spink County, SD

The radar

The Aberdeen radar (KABR), 20 km from the middle of the area, began a volume at 23:18 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 SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes: 30%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 10%
One or more gusts of 65 knots or more: 10%
Ten or more severe hail reports: 10%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 30%

Warnings issued inside it

2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Aug 23, 6:30 PM CDT	Tornado Warning	ABR	Edmunds, McPherson	30 min
Aug 23, 7:24 PM CDT	Flash Flood Warning	ABR	Edmunds, Faulk, McPherson	6 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 11.3 hours before the alert went out and 58 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: 119 J/kg
Mixed-layer CIN: -15 J/kg
Mixed-layer LCL: 564 m above ground
0-6 km bulk shear: 42 kt
0-1 km storm-relative helicity: 119 m²/s²
0-3 km storm-relative helicity: 168 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

634 
WWUS20 KWNS 232316
SEL4  
SPC WW 232316
SDZ000-240300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 474
NWS STORM PREDICTION CENTER NORMAN OK
615 PM CDT SAT AUG 23 2014

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  A SMALL PART OF NORTH CENTRAL AND NORTHEAST SOUTH DAKOTA

* EFFECTIVE THIS SATURDAY EVENING FROM 615 PM UNTIL 1000 PM CDT.

* PRIMARY THREATS INCLUDE...
  A COUPLE TORNADOES POSSIBLE

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH OF ABERDEEN
SOUTH DAKOTA TO 55 MILES SOUTH OF ABERDEEN SOUTH DAKOTA.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

&&

DISCUSSION...ISOLATED SUPERCELL WILL MOVE NWD ACROSS THE SURFACE
WARM FRONT...AND ADDITIONAL STORM DEVELOPMENT MAY OCCUR IN THE NEXT
COUPLE OF HOURS.  A TORNADO OR TWO WILL BE POSSIBLE IN THE ZONE OF
ENHANCED LOW-LEVEL SHEAR NEAR AND N OF THE BOUNDARY...GIVEN AT LEAST
WEAK SURFACE-BASED BUOYANCY AND BOUNDARY LAYER DEWPOINTS IN THE
UPPER 60S.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.
MEAN STORM MOTION VECTOR 18025.


...THOMPSON

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 23, 2:07 PM CDT	Mesoscale Discussion	SPC	Custer, Fall River, Oglala Lakota	113 min
Aug 23, 3:49 PM CDT	Mesoscale Discussion	SPC	Beadle, Brown, Campbell, Clark, Codington, Day and 15 more	116 min

Nearby

Tornado Watches in South Dakota, 2014 Every tornado watch in 2014

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.