Alert archive / Alabama / Tornado Watches in 2012

Tornado Watch 680

December 10, 201224 counties in Alabama; 7 parishes in Louisiana; 9 counties in Mississippi

The Storm Prediction Center issued this tornado watch at Dec 10, 2012, 8:51 AM CST for 24 counties in Alabama; 7 parishes in Louisiana; 9 counties in Mississippi. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Dec 10, 2012, 8:51 AM CST (14:51 UTC)
Expired: Dec 10, 2012, 3:00 PM CST
In force: 6 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 40 counties

Autauga County, AL, Barbour County, AL, Bullock County, AL, Chambers County, AL, Chilton County, AL, Choctaw County, AL, Clarke County, AL, Dallas County, AL, Elmore County, AL, Greene County, AL, Hale County, AL, Lee County, AL, Lowndes County, AL, Macon County, AL, Marengo County, AL, Mobile County, AL, Montgomery County, AL, Perry County, AL, Pike County, AL, Russell County, AL, Sumter County, AL, Tallapoosa County, AL, Washington County, AL, Wilcox County, AL, Jefferson Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS, Wayne County, MS

The radar

The Mobile radar (KMOB), 76 km from the middle of the area, began a volume at 14:53 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: 40%
One or more EF2 to EF5 tornadoes: 20%
Ten or more severe wind reports: 40%
One or more gusts of 65 knots or more: 30%
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

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

Issued	Product	Office	Counties	Lasted
Dec 10, 8:58 AM CST	Severe Thunderstorm Warning	LIX	Ascension, Saint James, Saint John the Baptist	47 min
Dec 10, 9:00 AM CST	Severe Thunderstorm Warning	MOB	Wayne	60 min
Dec 10, 9:10 AM CST	Severe Thunderstorm Warning	LIX	Pearl River	65 min
Dec 10, 9:19 AM CST	Tornado Warning	LIX	Pearl River	26 min
Dec 10, 9:23 AM CST	Severe Thunderstorm Warning	MOB	Perry	52 min
Dec 10, 9:25 AM CST	Severe Thunderstorm Warning	LIX	Saint Tammany, Tangipahoa, Washington	65 min
Dec 10, 9:41 AM CST	Tornado Warning	LIX	Pearl River	49 min
Dec 10, 9:43 AM CST	Severe Thunderstorm Warning	LIX	Assumption, Lafourche, Saint Charles, Saint James, Saint John the Baptist	47 min
Dec 10, 9:53 AM CST	Severe Thunderstorm Warning	MOB	Choctaw	52 min
Dec 10, 10:02 AM CST	Severe Thunderstorm Warning	MOB	Greene, Perry, Wayne	58 min
Dec 10, 10:05 AM CST	Severe Thunderstorm Warning	BMX	Dallas	25 min
Dec 10, 10:10 AM CST	Severe Thunderstorm Warning	BMX	Autauga, Lowndes	35 min
Dec 10, 10:17 AM CST	Severe Thunderstorm Warning	LIX	Hancock, Pearl River	22 min
Dec 10, 10:18 AM CST	Severe Thunderstorm Warning	LIX	Saint Tammany	42 min
Dec 10, 10:26 AM CST	Severe Thunderstorm Warning	MOB	Greene, Perry, Stone	64 min
Dec 10, 10:29 AM CST	Severe Thunderstorm Warning	BMX	Dallas	31 min
Dec 10, 10:31 AM CST	Severe Thunderstorm Warning	MOB	Washington	49 min
Dec 10, 10:36 AM CST	Tornado Warning	MOB	Choctaw, Washington	40 min
Dec 10, 10:58 AM CST	Tornado Warning	MOB	Clarke	41 min
Dec 10, 11:32 AM CST	Severe Thunderstorm Warning	MOB	Mobile, Washington	42 min
Dec 10, 11:36 AM CST	Severe Thunderstorm Warning	MOB	Clarke, Monroe, Wilcox	54 min
Dec 10, 12:09 PM CST	Severe Thunderstorm Warning	MOB	Baldwin, Clarke, Monroe	47 min
Dec 10, 12:18 PM CST	Severe Thunderstorm Warning	MOB	Butler, Monroe, Wilcox	42 min
Dec 10, 12:30 PM CST	Severe Thunderstorm Warning	MOB	Clarke, Conecuh, Monroe	28 min
Dec 10, 12:32 PM CST	Severe Thunderstorm Warning	MOB	Butler, Wilcox	29 min
Dec 10, 1:13 PM CST	Severe Thunderstorm Warning	BMX	Elmore, Lowndes, Montgomery	47 min
Dec 10, 1:41 PM CST	Severe Thunderstorm Warning	BMX	Bullock, Lee, Macon, Tallapoosa	64 min
Dec 10, 1:55 PM CST	Tornado Warning	BMX	Macon	22 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

Slidell Radar S, LA (KSIL), launched 12:00Z, 2.9 hours before the alert went out and 126 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: 767 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 488 m above ground
0-6 km bulk shear: 61 kt
0-1 km storm-relative helicity: 237 m²/s²
0-3 km storm-relative helicity: 263 m²/s²
Significant tornado parameter: 1.3
Supercell composite: 7.9

Open this sounding in Storm Lab

The text

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

797 
WWUS20 KWNS 101449
SEL0
SPC WW 101449
ALZ000-LAZ000-MSZ000-CWZ000-102100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 680
NWS STORM PREDICTION CENTER NORMAN OK
850 AM CST MON DEC 10 2012

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

       CENTRAL AND SOUTHWEST ALABAMA
       SOUTHEAST LOUISIANA
       SOUTHEAST MISSISSIPPI
       COASTAL WATERS

EFFECTIVE THIS MONDAY MORNING AND AFTERNOON FROM 850 AM UNTIL 300
PM CST.

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

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES EAST AND WEST OF A LINE FROM 25 MILES SOUTH SOUTHEAST OF
SLIDELL LOUISIANA TO 30 MILES NORTH NORTHWEST OF SELMA ALABAMA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU0).

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.

OTHER WATCH INFORMATION...CONTINUE...WW 679...

DISCUSSION...A BROKEN LINE OF THUNDERSTORMS OVER PARTS OF SOUTHEAST
MS AND SOUTHEAST LA WILL PROGRESS EASTWARD ACROSS THE WATCH AREA
TODAY.  INSTABILITY IS ONLY MARGINAL...BUT LOW AND MID LEVEL
VERTICAL SHEAR ARE QUITE STRONG AND SUPPORTIVE OF OCCASIONAL
ROTATING STORMS.  DAMAGING WINDS AND ISOLATED TORNADOES ARE THE MAIN
THREAT.

AVIATION...TORNADOES AND 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
450. MEAN STORM MOTION VECTOR 25035.


...HART

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 10, 7:31 AM CST	Mesoscale Discussion	SPC	Choctaw, Mobile, Washington	119 min
Dec 10, 10:24 AM CST	Mesoscale Discussion	SPC	Autauga, Baldwin, Bullock, Butler, Chambers, Chilton and 22 more	2 hr
Dec 10, 12:52 PM CST	Mesoscale Discussion	SPC	Baldwin, Barbour, Bullock, Butler, Chambers, Coffee and 18 more	113 min
Dec 9, 8:38 PM CST	Mesoscale Discussion	SPC	Beauregard, Bienville, Bossier, Caddo, Caldwell, Claiborne and 15 more	67 min
Dec 9, 9:59 PM CST	Mesoscale Discussion	SPC	Concordia, East Carroll, Franklin, Madison, Tensas	61 min
Dec 9, 11:24 PM CST	Mesoscale Discussion	SPC	Caldwell, Catahoula, East Carroll, Franklin, Grant, LaSalle and 6 more	66 min
Dec 10, 4:07 AM CST	Mesoscale Discussion	SPC	Acadia, Allen, Ascension, Assumption, Avoyelles, Cameron and 23 more	113 min
Dec 10, 5:44 AM CST	Tornado Watch	SPC	Ascension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 10 more	5 hr

Nearby

Tornado Watches in Alabama, 2012 Tornado Watches in Mississippi, 2012 Tornado Watches in Louisiana, 2012 Every tornado 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.