Alert archive / Mississippi / Severe Thunderstorm Watches in 2012

Severe Thunderstorm Watch 552

August 3, 201217 counties in Alabama; 24 counties in Mississippi

The Storm Prediction Center issued this severe thunderstorm watch at Aug 3, 2012, 12:14 PM CDT for 17 counties in Alabama; 24 counties in Mississippi. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Aug 3, 2012, 12:14 PM CDT (17:14 UTC)
Expired: Aug 3, 2012, 5:54 PM CDT
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 41 counties

Autauga County, AL, Bibb County, AL, Chilton County, AL, Coosa County, AL, Dallas County, AL, Elmore County, AL, Greene County, AL, Hale County, AL, Jefferson County, AL, Lowndes County, AL, Marengo County, AL, Montgomery County, AL, Perry County, AL, Pickens County, AL, Shelby County, AL, Sumter County, AL, Tuscaloosa County, AL, Attala County, MS, Carroll County, MS, Choctaw County, MS, Clay County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Kemper County, MS, Lauderdale County, MS, Leake County, MS, Leflore County, MS, Lowndes County, MS, Madison County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Noxubee County, MS, Oktibbeha County, MS, Rankin County, MS, Scott County, MS, Webster County, MS, Winston County, MS, Yazoo County, MS

The radar

The Columbus AFB radar (KGWX), 100 km from the middle of the area, began a volume at 17:16 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: 5%
One or more EF2 to EF5 tornadoes: 2%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 20%
Ten or more severe hail reports: 20%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Aug 3, 1:30 PM CDT	Severe Thunderstorm Warning	JAN	Clay	45 min

Discussions around it

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

The nearest sounding before it

Jackson, MS (KJAN), launched 12:00Z, 5.2 hours before the alert went out and 150 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: 2849 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 681 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: -19 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.9

Open this sounding in Storm Lab

The text

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

971 
WWUS20 KWNS 031714
SEL2
SPC WW 031714
ALZ000-MSZ000-040000-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 552
NWS STORM PREDICTION CENTER NORMAN OK
1215 PM CDT FRI AUG 3 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       CENTRAL ALABAMA
       CENTRAL MISSISSIPPI

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 1215 PM UNTIL
700 PM CDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 50
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTH
SOUTHWEST OF GREENWOOD MISSISSIPPI TO 50 MILES NORTHEAST OF SELMA
ALABAMA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...DIFFERENTIAL HEATING ON THE S EDGE OF A CLOUD BAND
ACROSS NRN MS/AL WILL PROMOTE NEW THUNDERSTORM DEVELOPMENT THIS
AFTERNOON ACROSS CENTRAL MS/AL.  STRONG INSTABILITY IS ALREADY
PRESENT ACROSS THIS AREA /MLCAPE AOA 3000 J PER KG/...AND EFFECTIVE
BULK SHEAR OF 25-30 KT WILL SUPPORT A RISK FOR ORGANIZED MULTICELL
CLUSTERS CAPABLE OF PRODUCING DAMAGING DOWNBURST WINDS AND ISOLATED
LARGE HAIL THIS AFTERNOON.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 36015.


...THOMPSON

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 3, 11:56 AM CDT	Mesoscale Discussion	SPC	Bibb, Choctaw, Dallas, Fayette, Greene, Hale and 8 more	64 min
Aug 3, 3:33 PM CDT	Mesoscale Discussion	SPC	Autauga, Bibb, Chilton, Coosa, Dallas, Elmore and 12 more	57 min

Nearby

Severe Thunderstorm Watches in Mississippi, 2012 Severe Thunderstorm Watches in Alabama, 2012 Every severe thunderstorm watch in 2012

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.