[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 231629
SWOMCD
SPC MCD 231628 
LAZ000-231930-

MESOSCALE DISCUSSION 2252
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT THU SEP 23 2004

AREAS AFFECTED...PORTIONS SRN LA

CONCERNING...SEVERE TSTM POTENTIAL - T.S. IVAN TORNADOES 

VALID 231628Z - 231930Z

POTENTIAL FOR A FEW SUPERCELLS AND ASSOCIATED BRIEF TORNADOES IS
EXPECTED TO INCREASE GRADUALLY THROUGH EARLY-MID AFTERNOON AS
BOUNDARY LAYER CONTINUES TO HEAT/DESTABILIZE...HELPING TO INCREASE
CONVECTIVE COVERAGE IN CORRIDOR OF FAVORABLE LOW LEVEL VERTICAL
SHEAR. AREA WILL BE MONITORED FOR PSBL WW.

STRENGTHENING/EXPANDING BAND OF CONVECTION -- EVIDENT AT 16Z FROM
NEAR ARA SEWD OVER ST MARY/WRN TERREBONNE PARISHES THEN SWD OVER
GULF -- SHOULD SHIFT WWD ACROSS DISCUSSION AREA AND APPEARS TO 
REPRESENT LARGEST PROBABILITIES ON MESO-BETA SCALE.  MODIFIED LIX
RAOB AND RUC/ETA FCST SOUNDINGS SUGGEST MLCAPES 1000-1500 J/KG
POSSIBLE AS SFC TEMPS WARM INTO LOW-MID 80S F...IN RELATIVELY CLOUD
FREE AREAS BETWEEN EXISTING CLOUD/PRECIP BANDS.  ASSOCIATED
DIFFERENTIAL HEATING BOUNDARIES MAY SERVE TO ENHANCE LOW LEVEL
CONVERGENCE/SHEAR/VORTICITY AND POTENTIAL FOR ROTATION IN ANY
SUSTAINED CONVECTION WITH WHICH THEY INTERACT. AFOREMENTIONED
SOUNDINGS AND VWP DATA SHOW WEAK MIDLEVEL FLOW -- I.E. 500 MB WINDS
AROUND 10 KT -- THOUGH NARROW CORRIDOR OF STRONGER MIDLEVEL WINDS IS
LIKELY OVER COASTAL SWRN LA WHERE NO OBSERVATIONAL SAMPLING IS
PRESENT.  HOWEVER...EXPECT ENLARGED LOW LEVEL HODOGRAPHS -- WITH 0-1
KM SRH UP TO NEAR 300 J/KG -- JUXTAPOSED WITH WEAKENING CINH AND
INCREASING BUOYANCY.  LCH VWP SHOWS HODOGRAPH EXPANDING WITH TIME
AND THIS TREND SHOULD CONTINUE THROUGH AT LEAST MIDAFTERNOON AS
CENTER OF IVAN PASSES S AND SW OF THAT LOCATION.

REF NHC ADVISORIES -- I.E. WMO HEADER WTNT24 KNHC -- FOR LATEST
INFORMATION REGARDING TRACK/INTENSITY GUIDANCE AND TROPICAL
WATCHES/WARNINGS FOR IVAN.

..EDWARDS.. 09/23/2004

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

ATTN...WFO...LIX...LCH...

29749314 29939327 30419353 30709344 30889313 30899292
30829250 30469143 30069099 29579078 29139070 28889067
28759071 28739098 28809120 28979150 29499266 29649297 

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