Alert archive / Louisiana / Tornado Watches in 2011

Tornado Watch 9

February 1, 201152 parishes in Louisiana; 18 counties in Mississippi

The Storm Prediction Center issued this tornado watch at Feb 1, 2011, 8:40 AM CST for 52 parishes in Louisiana; 18 counties in Mississippi. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Feb 1, 2011, 8:40 AM CST (14:40 UTC)
Expired
Feb 1, 2011, 3:00 PM CST
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt
All 70 counties

Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Cameron Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jackson Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, LaSalle Parish, LA, Livingston Parish, LA, Madison Parish, LA, Natchitoches Parish, LA, Orleans Parish, LA, Ouachita Parish, LA, Plaquemines Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Richland Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Tensas Parish, LA, Terrebonne Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Winn Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Franklin County, MS, Hinds County, MS, Jefferson County, MS, Jefferson Davis County, MS, Lawrence County, MS, Lincoln County, MS, Madison County, MS, Marion County, MS, Pike County, MS, Rankin County, MS, Simpson County, MS, Walthall County, MS, Warren 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
40%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
50%
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
10%
Six or more combined severe hail and wind reports
80%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Feb 1, 8:51 AM CSTSevere Thunderstorm WarningSHVNatchitoches, Winn38 min
Feb 1, 9:08 AM CSTTornado WarningLCHAllen, Beauregard, Calcasieu, Jefferson Davis37 min
Feb 1, 10:14 AM CSTSevere Thunderstorm WarningLCHAvoyelles, Evangeline, Rapides31 min
Feb 1, 10:39 AM CSTSevere Thunderstorm WarningJANCatahoula, Concordia51 min
Feb 1, 10:40 AM CSTSevere Thunderstorm WarningLCHAcadia, Avoyelles, Evangeline, Saint Landry50 min
Feb 1, 10:44 AM CSTSevere Thunderstorm WarningJANCatahoula, Concordia46 min
Feb 1, 11:01 AM CSTSevere Thunderstorm WarningLIXEast Feliciana, Pointe Coupee, West Feliciana59 min
Feb 1, 11:04 AM CSTSevere Thunderstorm WarningJANAdams41 min
Feb 1, 11:09 AM CSTSevere Thunderstorm WarningJANAdams36 min
Feb 1, 11:31 AM CSTSevere Thunderstorm WarningJANAdams, Franklin, Jefferson44 min
Feb 1, 11:32 AM CSTSevere Thunderstorm WarningLCHSaint Landry, Saint Martin28 min
Feb 1, 11:37 AM CSTSevere Thunderstorm WarningLIXEast Feliciana, Pointe Coupee, West Feliciana38 min
Feb 1, 12:00 PM CSTSevere Thunderstorm WarningLIXPointe Coupee, West Feliciana45 min
Feb 1, 12:16 PM CSTSevere Thunderstorm WarningLIXEast Baton Rouge, East Feliciana, Iberville, Pointe Coupee, West Baton Rouge, West Feliciana44 min
Feb 1, 12:45 PM CSTSevere Thunderstorm WarningLIXEast Feliciana, Saint Helena60 min
Feb 1, 12:53 PM CSTSevere Thunderstorm WarningLIXAscension, East Baton Rouge, East Feliciana, Iberville, Livingston, Saint Helena and 1 more57 min
Feb 1, 12:55 PM CSTSevere Thunderstorm WarningJANLawrence, Lincoln50 min
Feb 1, 1:16 PM CSTSevere Thunderstorm WarningJANCopiah, Rankin, Scott, Simpson, Smith44 min
Feb 1, 1:17 PM CSTSevere Thunderstorm WarningLIXLivingston, Saint Helena, Tangipahoa, Washington58 min
Feb 1, 1:41 PM CSTSevere Thunderstorm WarningLIXLivingston, Saint Tammany, Tangipahoa, Washington64 min
Feb 1, 1:44 PM CSTSevere Thunderstorm WarningJANCovington, Jefferson Davis, Lamar, Lawrence, Marion46 min
Feb 1, 2:11 PM CSTSevere Thunderstorm WarningLIXWashington49 min
Feb 1, 2:25 PM CSTSevere Thunderstorm WarningJANCovington, Forrest, Jefferson Davis, Jones, Lamar, Marion65 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

Lake Charles Mun, LA (KLCH), launched 12:00Z, 2.7 hours before the alert went out and 163 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-pSkew-T log-p diagram, Lake Charles Mun, LA at 12:00Z on 2011-02-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 672 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lake Charles Mun, LA at 12:00Z on 2011-02-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 381 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
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
672 J/kg
Mixed-layer CIN
-21 J/kg
Mixed-layer LCL
446 m above ground
0-6 km bulk shear
59 kt
0-1 km storm-relative helicity
381 m²/s²
0-3 km storm-relative helicity
478 m²/s²
Significant tornado parameter
1.7
Supercell composite
8.2

Open this sounding in Storm Lab

The text

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

540 
WWUS20 KWNS 011440
SEL9  
SPC WW 011440
LAZ000-MSZ000-CWZ000-012100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 9
NWS STORM PREDICTION CENTER NORMAN OK
840 AM CST TUE FEB 1 2011

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

       MUCH OF LOUISIANA
       WEST CENTRAL AND SOUTHWEST MISSISSIPPI
       COASTAL WATERS

EFFECTIVE THIS TUESDAY MORNING AND AFTERNOON FROM 840 AM UNTIL
300 PM 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 100 STATUTE
MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH OF NATCHEZ
MISSISSIPPI TO 45 MILES SOUTH 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...A STRONGLY FORCED SQUALL LINE MOVE QUICKLY EWD IN
CONJUNCTION WITH A SURFACE COLD FRONT PROGRESSING EWD FROM TX INTO
LA...AND STRONG MIDLEVEL TROUGH EJECTING ENEWD OVER TX/OK.  GRADUAL
SURFACE MOISTENING/DESTABILIZATION WILL SUPPORT CONVECTION BASED
NEAR THE SURFACE AS DEWPOINTS INCREASE INTO THE 60S...WHILE VERTICAL
SHEAR WILL BE VERY STRONG AND SUPPORTIVE OF EMBEDDED BOW/SUPERCELL
STRUCTURES IN THE LINE.  A FEW TORNADOES AND DAMAGING WINDS WILL BE
THE MAIN THREATS INTO THE AFTERNOON.

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 24045.


...THOMPSON

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 1, 6:46 AM CSTMesoscale DiscussionSPCAllen, Avoyelles, Bienville, Bossier, Caddo, Caldwell and 25 more119 min
Feb 1, 12:00 PM CSTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, East Feliciana, Iberia, Iberville and 24 more60 min
Feb 1, 1:23 PM CSTMesoscale DiscussionSPCAscension, Assumption, East Baton Rouge, Jefferson, Lafourche, Livingston and 12 more67 min
Feb 1, 1:03 PM CSTTornado WatchSPCClarke, Covington, Forrest, George, Greene, Hancock and 13 more7 hr
Feb 1, 3:44 PM CSTMesoscale DiscussionSPCGeorge, Greene, Hancock, Harrison, Jackson, Perry and 2 more61 min

Nearby

Tornado Watches in Louisiana, 2011Tornado Watches in Mississippi, 2011Every tornado watch in 2011

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.