Alert archive / Louisiana / Tornado Watches in 2012

Tornado Watch 142

April 5, 201222 parishes in Louisiana; 8 counties in Mississippi

The Storm Prediction Center issued this tornado watch at Apr 5, 2012, 3:56 AM CDT for 22 parishes in Louisiana; 8 counties in Mississippi. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Apr 5, 2012, 3:56 AM CDT (08:56 UTC)
Expired
Apr 5, 2012, 10:16 AM CDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
2.5 in
Strongest gust expected
60 kt
All 30 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Pointe Coupee 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 Tammany Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Amite County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Pike 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
10%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
80%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Apr 5, 4:25 AM CDTSevere Thunderstorm WarningLIXLafourche, Terrebonne17 min
Apr 5, 4:41 AM CDTSevere Thunderstorm WarningLIXLivingston, Saint Helena, Tangipahoa49 min
Apr 5, 5:09 AM CDTSevere Thunderstorm WarningLIXWashington51 min
Apr 5, 5:24 AM CDTSevere Thunderstorm WarningLIXJefferson, Lafourche, Plaquemines, Terrebonne47 min
Apr 5, 5:25 AM CDTSevere Thunderstorm WarningLIXSaint Tammany, Washington35 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 00:00Z, 8.9 hours before the alert went out and 104 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, Slidell Radar S, LA at 00:00Z on 2012-04-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 593 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, Slidell Radar S, LA at 00:00Z on 2012-04-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 8 square meters per square second.19395878Sfc1 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
593 J/kg
Mixed-layer CIN
-175 J/kg
Mixed-layer LCL
1126 m above ground
0-6 km bulk shear
42 kt
0-1 km storm-relative helicity
8 m²/s²
0-3 km storm-relative helicity
58 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.

601 
WWUS20 KWNS 050855
SEL2  
SPC WW 050855
LAZ000-MSZ000-CWZ000-051600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 142
NWS STORM PREDICTION CENTER NORMAN OK
355 AM CDT THU APR 5 2012

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

       SOUTHEASTERN LOUISIANA
       SOUTHERN MISSISSIPPI
       COASTAL WATERS

EFFECTIVE THIS THURSDAY MORNING FROM 355 AM UNTIL 1100 AM CDT.

TORNADOES...HAIL TO 2.5 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 105 STATUTE
MILES EAST AND WEST OF A LINE FROM 35 MILES NORTHWEST OF SLIDELL
LOUISIANA TO 30 MILES SOUTH OF HOUMA LOUISIANA.  FOR A COMPLETE
DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE
(WOUS64 KWNS WOU2).

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 141...

DISCUSSION...TSTMS...INCLUDING A FEW SUPERCELLS...EXPECTED TO
CONTINUE FORMING IN ZONE OF LOW LVL WAA/MOISTURE TRANSPORT ON
BACKSIDE OF RETREATING MESOHIGH AND IN SRN PART OF VORT LOBE MOVING
THROUGH BASE OF AR UPR LOW.  WEAK SFC FLOW SUGGESTS THAT SETUP IS
MOST FAVORABLE FOR LARGE HAIL...ESPECIALLY WITH ANY LONGER-LIVED
DISCRETE STORMS IN SRN HALF OF WW.  BUT RETREATING COOL DOME IS VERY
SHALLOW...AND MODERATE...VERY MOIST SW FLOW IS PRESENT JUST OFF THE
SFC ACROSS SRN LA.  AS FLOW AND FORCING STRENGTHEN LATER THIS
MORNING...POTENTIAL ALSO WILL EXIST FOR A TORNADO OR
TWO...ESPECIALLY NEAR OUTFLOW BOUNDARY REMNANT IN SE LA.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 26030.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 4, 8:25 PM CDTMesoscale DiscussionSPCAcadia, Allen, Ascension, Assumption, Beauregard, Calcasieu and 21 more95 min
Apr 4, 8:31 PM CDTMesoscale DiscussionSPCBienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 2 more119 min
Apr 5, 1:35 AM CDTMesoscale DiscussionSPCAvoyelles, Caldwell, Catahoula, Concordia, East Baton Rouge, East Carroll and 21 more85 min
Apr 5, 1:53 AM CDTTornado WatchSPCAcadia, Allen, Ascension, Avoyelles, Bienville, Caldwell and 36 more9 hr
Apr 5, 3:30 AM CDTMesoscale DiscussionSPCAcadia, Ascension, Assumption, Avoyelles, Caldwell, Catahoula and 43 more2 hr
Apr 5, 7:36 AM CDTMesoscale DiscussionSPCCaldwell, Catahoula, Concordia, East Carroll, Franklin, Jackson and 18 more54 min
Apr 5, 9:14 AM CDTSevere Thunderstorm WatchSPCGreene, Perry, Wayne8 hr
Apr 5, 10:41 AM CDTMesoscale DiscussionSPCGreene, Wayne94 min
Apr 5, 10:43 AM CDTSevere Thunderstorm WatchSPCClarke, Covington, Forrest, Franklin, Jasper, Jefferson Davis and 7 more4 hr
Apr 5, 12:09 PM CDTMesoscale DiscussionSPCAlcorn, Benton, DeSoto, Itawamba, Lafayette, Lee and 8 more96 min
Apr 5, 12:18 PM CDTSevere Thunderstorm WatchSPCAlcorn, Benton, Calhoun, Chickasaw, Coahoma, DeSoto and 16 more5 hr
Apr 5, 2:22 PM CDTMesoscale DiscussionSPCAlcorn, Benton, Calhoun, Chickasaw, DeSoto, Itawamba and 14 more53 min

Nearby

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