Alert archive / Louisiana / Mesoscale Discussions in 2003

Mesoscale Discussion 113

February 21, 200338 parishes in Louisiana; 9 counties in Mississippi; 11 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Feb 21, 2003, 5:50 PM CST for 38 parishes in Louisiana; 9 counties in Mississippi; 11 counties in Texas. It was in force for 115 min.

The area

The outline as issued.

The facts

Issued
Feb 21, 2003, 5:50 PM CST (23:50 UTC)
Expired
Feb 21, 2003, 7:45 PM CST
In force
115 min
Issued by
the Storm Prediction Center
All 58 counties

Acadia Parish, LA, Allen Parish, LA, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Jefferson Parish, LA, Lafayette Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Sabine 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, Vermilion Parish, LA, Vernon Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Franklin County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pike County, MS, Walthall County, MS, Wilkinson County, MS, Angelina County, TX, Chambers County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Nacogdoches County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, San Augustine County, TX, Tyler County, TX

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 11.8 hours before the alert went out and 79 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 2003-02-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 543 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 2003-02-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 253 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
543 J/kg
Mixed-layer CIN
-114 J/kg
Mixed-layer LCL
433 m above ground
0-6 km bulk shear
45 kt
0-1 km storm-relative helicity
253 m²/s²
0-3 km storm-relative helicity
274 m²/s²
Significant tornado parameter
0.0
Supercell composite
6.2

Open this sounding in Storm Lab

The text

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

294 
ACUS11 KWNS 212350
SWOMCD
SPC MCD 212350 
TXZ000-LAZ000-MSZ000-220145-

MESOSCALE DISCUSSION 0113
NWS STORM PREDICTION CENTER NORMAN OK
0550 PM CST FRI FEB 21 2003

AREAS AFFECTED...SE TX...SRN LA...SW MS

CONCERNING...TORNADO WATCH 12...

VALID 212350Z - 220145Z

TORNADO THREAT CONTINUES MAINLY OVER LA PORTION WW AREA...AND
APPEARS TO BE INCREASING IN PORTIONS S-CENTRAL/SERN LA.  



SURFACE ANALYSIS SHOWS CYCLONE MOVING NEWD INTO W-CENTRAL/NWRN
LA...WITH RESIDUAL OUTFLOW BOUNDARY AND EFFECTIVE WARM FRONT SEWD
ACROSS PORTIONS NATCHITOCHES/RAPIDES PARISHES TO BETWEEN HUM-MSY.
 EXPECT THIS BOUNDARY TO LIFT NEWD THROUGH REMAINDER EVENING
ACROSS ERN LA AND SW MS...AMIDST STRONG ISALLOBARIC FORCING AND
LOW LEVEL WAA/DESTABILIZATION.	THIS WILL EXTEND FAVORABLE AIR
MASS FOR SURFACE BASED SUPERCELLS INTO PORTIONS SWRN MS AND MORE
OF SERN LA.  



CONFLUENCE LINE IS ANALYZED SWD FROM CYCLONE ACROSS PORTIONS
ALLEN...JEFF DAVIS AND ERN CAMERON PARISHES...AND SHOULD SHIFT
EWD 15-20 KT ACROSS CENTRAL/SRN LA NEXT SEVERAL HOURS.	W OF THAT
LINE...BOUNDARY LAYER FLOW HAS VEERED...REDUCING LOW LEVEL SHEAR
AND CONVERGENCE..THOUGH SEVERE IS STILL POSSIBLE.  E OF
CONFLUENCE LINE AND ALONG/S OF OUTFLOW BOUNDARY...FLOW REMAINS
RELATIVELY BACKED.  MODIFIED VWP HODOGRAPHS AND RUC2 FORECAST
SOUNDINGS INDICATE 300-600 J/KG 0-3 KM SRH.  TSTMS DEVELOPING
OVER COASTAL AREAS LA...AND ENTERING WW FROM GULF...WILL MOVE
INTO PROGRESSIVELY MORE FAVORABLE VERTICAL SHEAR AS THEY APPROACH
OUTFLOW BOUNDARY.  BRN SHEAR RANGES FROM 40-50 J/KG OVER SWRN
CORNER LA TO NEARLY 150 J/KG ALONG AND JUST N OF OUTFLOW
BOUNDARY.  

..EDWARDS.. 02/21/2003

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

30619479 31709479 31629225 31548972 30468972 29378972
29459225 29539479

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 21, 1:43 AM CSTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 6 more2 hr
Feb 21, 4:35 AM CSTMesoscale DiscussionSPCAscension, Assumption, Avoyelles, Concordia, East Baton Rouge, East Feliciana and 16 more115 min
Feb 21, 9:02 AM CSTMesoscale DiscussionSPCBeauregard, Calcasieu, Cameron, Sabine, Vernon58 min
Feb 21, 9:40 AM CSTTornado WatchSPCAcadia, Allen, Beauregard, Calcasieu, Caldwell, Cameron and 11 more6 hr
Feb 21, 11:47 AM CSTMesoscale DiscussionSPCAcadia, Allen, Beauregard, Calcasieu, Cameron, Evangeline and 4 more118 min
Feb 21, 3:32 PM CSTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Evangeline, Jefferson Davis, Vernon118 min
Feb 21, 3:40 PM CSTTornado WatchSPCAcadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 32 more6 hr
Feb 21, 5:20 PM CSTMesoscale DiscussionSPCClaiborne, East Carroll, Franklin, Jackson, Lincoln, Madison and 5 more4 hr
Feb 21, 2:43 AM CSTMesoscale DiscussionSPCDimmit, Edwards, Frio, Kinney, La Salle, Maverick and 5 more3 hr
Feb 21, 3:53 AM CSTMesoscale DiscussionSPCAransas, Austin, Brazoria, Calhoun, Colorado, Fort Bend and 13 more3 hr
Feb 21, 4:10 AM CSTSevere Thunderstorm WatchSPCAtascosa, Bandera, Bastrop, Bexar, Blanco, Brazos and 26 more6 hr
Feb 21, 4:25 AM CSTTornado WatchSPCAustin, Brazoria, Brazos, Burleson, Calhoun, Colorado and 15 more6 hr
Feb 21, 5:58 AM CSTMesoscale DiscussionSPCAtascosa, Bandera, Bastrop, Bexar, Blanco, Brazos and 26 more2 hr
Feb 21, 6:16 AM CSTMesoscale DiscussionSPCAustin, Brazoria, Brazos, Burleson, Calhoun, Colorado and 17 more119 min
Feb 21, 1:30 PM CSTMesoscale DiscussionSPCHardin, Harris, Jasper, Liberty, Montgomery, Newton and 3 more2 hr

Nearby

Mesoscale Discussions in Louisiana, 2003Mesoscale Discussions in Texas, 2003Mesoscale Discussions in Mississippi, 2003Every mesoscale discussion in 2003

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.