Friday, May 16, 2008

MESO: Mesoscale Discussion 0943

ACUS11 KWNS 161032
SWOMCD
SPC MCD 161032
MSZ000-LAZ000-161330-

MESOSCALE DISCUSSION 0943
NWS STORM PREDICTION CENTER NORMAN OK
0532 AM CDT FRI MAY 16 2008

AREAS AFFECTED...SOUTHEAST LA

CONCERNING...HEAVY RAINFALL

VALID 161032Z - 161330Z

HEAVY CONVECTIVE RAINFALL RATES OF 1-2 INCHES PER HOUR ARE LIKELY TO
PERSIST ACROSS PARTS OF SOUTHEAST LA EARLY THIS MORNING AS NORTH
GULF MCS SPREADS NEWD ALONG STALLED FRONTAL ZONE BISECTING MS DELTA.


DEEP-LAYER FRONTAL ZONE HAS STALLED WITHIN MODEST MEAN-LAYER WSWLY
FLOW FROM THE WRN GULF NEWD ACROSS SERN LA EARLY TODAY. RECENT
INCREASE IN DEEP CONVECTION ALONG THIS BOUNDARY COULD BE RELATED TO
1) NOCTURNAL STRENGTHENING OF LLJ...AND/OR 2) LIFT WITH APPROACH OF
MID/UPPER LEVEL WAVE/MCV ASSOCIATED WITH LARGE MCS OFF THE TX/LA
GULF COAST. TPW IMAGERY FROM CIRA INDICATES A PW PLUME WITH VALUES
AOA 2 INCHES ACROSS THE REGION. THIS RICH MOISTURE WAS LIKELY
CONTRIBUTING TO EXCESSIVE RAINFALL RATES WITH OVER 2 INCHES PER HOUR
RECENTLY OBSERVED IN NEW ORLEANS.

WEAK LARGE SCALE HEIGHT FALLS WILL FURTHER AID LOW LEVEL CONVERGENCE
AND LIFT ALONG THE FRONTAL ZONE THROUGH THIS MORNING. IN
ADDITION...GENERALLY WEAK FORWARD PROPAGATION VECTORS ACROSS THE NRN
GULF SUGGEST ONGOING MCS ACTIVITY WILL HAVE SOME TENDENCY TO
BACKBUILD BEFORE THE ENTIRE COMPLEX MOVES THROUGH LATER THIS
MORNING. LATEST HIREZ WRF-ARW APPEARS TO DEPICT BOTH THE FRONTAL
CONVECTION AND THE GULF MCS WELL. ONGOING HEAVY RAINFALL OCCURRING
ALONG THE FRONTAL BAND WILL ONLY BE EXACERBATED AS ANOTHER ROUND OF
HEAVY RAIN ACCOMPANIES THE MCS MOVING ACROSS THE SAME AREAS LATER
THIS MORNING.

..CARBIN.. 05/16/2008

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

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

29098939 28929092 29509143 30268976 30258869

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