Graphic for MPD #0763
MESOSCALE PRECIPITATION DISCUSSION 0763
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
852 PM EDT TUE AUG 29 2017

AREAS AFFECTED...SOUTHEAST TX...SW & CENTRAL LA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 300050Z - 300630Z

SUMMARY...HARVEY CONTINUES TO SHIFT EAST WITH EXPANDING MODERATE
TO HEAVY RAINS TO STAY FOCUSED ALONG SW-NE ORIENTED DEFORMATION
ZONE.

DISCUSSION...00Z SFC ANALYSIS AND LATE DAY VISIBLE LOOP ON GOES-16
DEPICTS A MORE CONCENTRIC BUT STRONGER INNER CORE OF TS HARVEY
ABOUT 50 NMI SOUTH OF SABINE PASS WITH A STRENGTHENING BAND
ARCHING FROM ACTIVE CONVECTION NEAR SABINE PASS ALONG THE SW LA
COAST WITH ADDITIONAL WEAKER FEED CU BANDS STREAKING SE TO NW
ACROSS CENTRAL LA.  THESE BANDS CONTINUE TO INTERSECT SW TO NE
ORIENTED MID-LEVEL DEFORMATION BAND (OLD DISCONNECTED TROWAL FROM
WARM CONVEYOR EAST OF 90W CURRENTLY).  00Z RAOBS FROM LCH/SHV
SUPPORT THE MORE SATURATED ENVIRONMENT THOUGH SOME DRY AIR
ENTRAINMENT IS NOTED IN THE 7-5H LAYER.

WARM GULF (LOW 80S T/MID-UPPER 70S TDS) CONTINUES TO BE SOURCE OF
AMPLE LOW LEVEL LATENT HEAT TO KEEP INSTABILITY MAINTAINED AROUND
1000-1500 J/KG THOUGH WITHOUT CONVERGENCE FROM A MORE FOCUSED BAND
CONVECTION HAS REMAINED VERY SHALLOW AND SCATTERED UNTIL
INTERCEPTING THE PERPENDICULAR ORIENTED DEFORMATION ZONE.  AS SUCH
PERSISTENT MODERATE TO HVY WARM SHOWERS WITH EMBEDDED CONVECTIVE
ELEMENTS CONTINUE TO LEAD TO 1.5-2"/HR RATES HIGHER CLOSER TO THE
SOURCE REGION OF THE GULF.  EXPANDING SELY FLOW ACROSS CENTRAL LA
HAS ALSO BEEN EXPANDING THE AREA OF INTERSECTION IN THE
DEFORMATION ZONE ACROSS FAR E TX TOWARD POE/ESF AND EVENTUALLY
TVR/HEZ.  GOES-16 3 CHANNEL WV SUITE ALSO DEPICTS THE FAVORABLE
BROAD ANTICYCLONIC ARCH ACROSS E TX ANGLING BACK TOWARD RIGHT
ENTRANCE REGION OF POLAR JET CROSS THE LOWER TN VALLEY...THIS WILL
ALSO ALLOW FOR BROAD LARGER SCALE ASCENT FURTHER NORTH EXPANDING
THE AREA OF MODERATE TO HEAVY SHOWERS.  ORIENTATION OF THE TRACK
OF HARVEY EAST AND EVENTUALLY NORTHEAST SHOULD HELP TO KEEP THE
DEFORMATION ZONE FAIRLY STATIC INCREASING DURATION OF 1"/HR RATES
LEADING TO 3-4" TOTALS TOWARD 07Z.  TOTALS OF 4-6" ARE POSSIBLE
NEAR GREATEST PROXIMITY (INCREASED FLOW/FLUX/INSTABILITY) ACROSS
COASTAL SE TX/SW LA) TO CENTER OF HARVEY.

AT THIS TIME GREATEST UNCERTAINTY REMAINS ACROSS SOUTH CENTRAL LA
WHERE BANDS MAY INCREASE IN FOCUS SUPPORTING A TRAINING PROFILE OF
STRONGER/DEEPER CONVECTION LIKELY NEAR/AIDED BY THE FRONTAL ZONE
ASCENT.  HI-RES GUIDANCE (HRRR/ARW/NAM-CONEST/HREFV2 MEAN)
SUGGESTS FURTHER NORTH BAND NORTH OF I-10 THOUGH ALL SUGGEST A
NORTHWARD TURN OF HARVEY...WHILE THE RAP HUGS THE COAST WITH THE
BAND SOUTH OF I-10 BUT SHIFTS HARVEY MORE EAST.  CURRENT TRENDS
WOULD TIP TOWARD THE RAP...BUT 2-3" INCHES ALONG THE BAND OVER
EITHER AREA DUE TO SATURATED SOILS WOULD BE PROBLEMATIC FOR
POTENTIAL FOR FLASH FLOODING.       

GALLINA

ATTN...WFO...HGX...JAN...LCH...SHV...

ATTN...RFC...LMRFC...WGRFC...

LAT...LON   32339156 31949135 31309197 30999223 30619199
            30209190 29549218 29639287 29639371 29559414
            29769448 30739461 31649369 32169276


Last Updated: 852 PM EDT TUE AUG 29 2017