Alert archive / Mississippi / Tornado Watches in 2012

Tornado Watch 679

December 10, 201216 parishes in Louisiana; 18 counties in Mississippi

The Storm Prediction Center issued this tornado watch at Dec 10, 2012, 5:44 AM CST for 16 parishes in Louisiana; 18 counties in Mississippi. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Dec 10, 2012, 5:44 AM CST (11:44 UTC)
Expired: Dec 10, 2012, 11:00 AM CST
In force: 5 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

All 34 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Clarke County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, Jasper County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pike County, MS, Simpson County, MS, Smith County, MS, Walthall County, MS, Wilkinson County, MS

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: 30%
One or more gusts of 65 knots or more: 20%
Ten or more severe hail reports: 5%
One or more hailstones of 2 inches or more: 5%
Six or more combined severe hail and wind reports: 50%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Dec 10, 6:14 AM CST	Tornado Warning	JAN	Smith	20 min
Dec 10, 6:31 AM CST	Tornado Warning	LIX	East Feliciana, Saint Helena	29 min
Dec 10, 6:52 AM CST	Severe Thunderstorm Warning	JAN	Simpson, Smith	68 min
Dec 10, 6:55 AM CST	Severe Thunderstorm Warning	LIX	East Baton Rouge, East Feliciana, Livingston, Saint Helena, West Baton Rouge	35 min
Dec 10, 7:09 AM CST	Severe Thunderstorm Warning	JAN	Jefferson Davis, Lawrence, Marion	51 min
Dec 10, 7:23 AM CST	Severe Thunderstorm Warning	LIX	East Baton Rouge, Livingston, Saint Helena, West Baton Rouge	37 min
Dec 10, 7:24 AM CST	Severe Thunderstorm Warning	LIX	Tangipahoa, Washington	36 min
Dec 10, 7:33 AM CST	Tornado Warning	LIX	Washington	27 min
Dec 10, 7:41 AM CST	Severe Thunderstorm Warning	JAN	Covington, Jefferson Davis	44 min
Dec 10, 7:45 AM CST	Tornado Warning	LIX	Livingston, Saint Helena	30 min
Dec 10, 7:53 AM CST	Tornado Warning	LIX	Washington	37 min
Dec 10, 7:56 AM CST	Severe Thunderstorm Warning	LIX	Livingston, Saint Helena, Tangipahoa	34 min
Dec 10, 8:14 AM CST	Tornado Warning	JAN	Marion	40 min
Dec 10, 8:16 AM CST	Severe Thunderstorm Warning	JAN	Jones	44 min
Dec 10, 8:20 AM CST	Severe Thunderstorm Warning	LIX	Ascension, Assumption, Iberville, Saint James	40 min
Dec 10, 8:23 AM CST	Severe Thunderstorm Warning	LIX	Saint Tammany, Tangipahoa, Washington	52 min
Dec 10, 8:39 AM CST	Severe Thunderstorm Warning	JAN	Clarke, Lauderdale	40 min
Dec 10, 8:45 AM CST	Severe Thunderstorm Warning	JAN	Forrest, Lamar	45 min
Dec 10, 8:46 AM CST	Severe Thunderstorm Warning	LIX	East Baton Rouge, Livingston, Saint Helena, Saint Tammany, Tangipahoa	29 min
Dec 10, 8:54 AM CST	Tornado Warning	LIX	Ascension, Livingston	36 min
Dec 10, 8:58 AM CST	Severe Thunderstorm Warning	LIX	Ascension, Saint James, Saint John the Baptist	47 min
Dec 10, 9:10 AM CST	Severe Thunderstorm Warning	LIX	Washington	65 min
Dec 10, 9:19 AM CST	Tornado Warning	LIX	Washington	26 min
Dec 10, 9:20 AM CST	Severe Thunderstorm Warning	JAN	Forrest, Jones	40 min
Dec 10, 9:25 AM CST	Severe Thunderstorm Warning	LIX	Saint Tammany, Tangipahoa, Washington	65 min
Dec 10, 9:43 AM CST	Severe Thunderstorm Warning	LIX	Assumption, Lafourche, Saint Charles, Saint James, Saint John the Baptist	47 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 00:00Z, 11.7 hours before the alert went out and 135 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: 804 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 712 m above ground
0-6 km bulk shear: 48 kt
0-1 km storm-relative helicity: 226 m²/s²
0-3 km storm-relative helicity: 257 m²/s²
Significant tornado parameter: 1.1
Supercell composite: 5.0

Open this sounding in Storm Lab

The text

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

669 
WWUS20 KWNS 101146
SEL9
SPC WW 101146
LAZ000-MSZ000-CWZ000-101700-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 679
NWS STORM PREDICTION CENTER NORMAN OK
545 AM CST MON DEC 10 2012

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

       PARTS OF SOUTH CENTRAL AND SOUTHEAST LOUISIANA
       SOUTHWEST AND SOUTH CENTRAL MISSISSIPPI
       COASTAL WATERS

EFFECTIVE THIS MONDAY MORNING FROM 545 AM UNTIL 1100 AM CST.

TORNADOES...HAIL TO 1 INCH 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 55 MILES NORTH OF PINE BELT
MISSISSIPPI TO 15 MILES SOUTH SOUTHEAST OF INTRACOASTAL CITY
LOUISIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).

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...THUNDERSTORMS CONTINUE TO DEVELOP ALONG A PRE-FRONTAL
CONFLUENCE BAND FROM S CENTRAL LA INTO SW MS...WHERE A FEW ROTATING
STORMS HAVE BEEN NOTED IN THE PAST 1-2 HOURS.  BOUNDARY LAYER
DEWPOINTS RANGE FROM 68-70 F IN ADVANCE OF THE STORMS...WHERE
DEEP-LAYER VERTICAL SHEAR IS SUFFICIENT FOR SUPERCELLS.  THE
ENVIRONMENT SHOULD REMAIN SOMEWHAT FAVORABLE FOR A TORNADO OR TWO
AND ISOLATED DAMAGING WINDS THROUGH ABOUT MID MORNING...WITH A
GRADUALLY DIMINISHING THREAT THEREAFTER AS THE PRIMARY SHORTWAVE
TROUGH PIVOTS BY FARTHER TO THE N.

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 450.
MEAN STORM MOTION VECTOR 25040.


...THOMPSON

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
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, 7:31 AM CST	Mesoscale Discussion	SPC	Ascension, Assumption, Iberia, Jefferson, Lafourche, Livingston and 11 more	119 min
Dec 10, 8:51 AM CST	Tornado Watch	SPC	Jefferson, Orleans, Plaquemines, Saint Bernard, Saint Charles, Saint John the Baptist and 1 more	6 hr
Dec 10, 10:24 AM CST	Mesoscale Discussion	SPC	Orleans	2 hr

Nearby

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.