MESOSCALE PRECIPITATION DISCUSSION 0722
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
530 AM EDT FRI AUG 25 2017

AREAS AFFECTED...MIDDLE AND LOWER TX COAST

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 250927Z - 251500Z

SUMMARY...RAINFALL RATES NEAR 3 IN/HR WILL BE POSSIBLE ALONG
PORTIONS OF THE LOWER AND MIDDLE TX COAST IN ADVANCE OF HURRICANE
HARVEY THROUGH 15Z. WHILE TRAINING IS NOT EXPECTED TO BE
WIDESPREAD...FLASH FLOODING WILL BE POSSIBLE WHERE TRAINING
PERSISTS.

DISCUSSION...REGIONAL RADAR IMAGERY SHOWED THAT THE INITIAL OUTER
SPIRAL BANDS ASSOCIATED WITH HURRICANE HARVEY HAVE REACHED THE
LOWER AND MIDDLE TX COASTLINE. KCRP RADAR IMAGERY INDICATED
TRAINING ACROSS PORTIONS OF ARANSAS AND MATAGORDA ISLAND NATIONAL
WILDLIFE REFUGES WITH DUAL POL ESTIMATES NEAR 2 IN/HR ENDING AT
08Z. THE CLOSEST OBSERVATION FOUND NEAR THIS AREA OF TRAINING
COMES FROM A WUNDERGROUND.COM REPORTING STATION WITH RAINFALL OF
0.4 TO 0.5 INCHES IN 10-15 MINUTE CHUNKS OF TIME AS THE OUTER BAND
MOVED ACROSS. IR SATELLITE IMAGERY BETWEEN 08-09Z ALSO NOTED
ENHANCED OUTFLOW TO THE NORTH OF HARVEY WITH A PROMINENT CURVED
BAND FEATURE LOCATED TO THE NORTH AND EAST OF THE CENTER OF HARVEY.

AS HURRICANE HARVEY MOVES CLOSER TO LAND OVER THE NEXT 6
HOURS...SPIRAL BANDS WITHIN THE FRONT-RIGHT QUADRANT WILL CONTINUE
TO MOVE ACROSS THE TX COAST WITH THE GREATEST POTENTIAL FOR
TRAINING/STALLING OF THESE BANDS OCCURRING ALONG THE MIDDLE TX
COAST TIED TO THE ORIENTATION OF THE RAIN BANDS TO THE COAST AND
FRICTIONAL CONVERGENCE NOTED IN SURFACE OBSERVATIONS.

FARTHER DOWN THE TX COAST...STEADIER HEAVY RAINFALL LOCATED
BETWEEN THE OUTER SPIRAL BANDS AND THE EYEWALL OF HARVEY VISIBLE
ON KBRO RADAR SHOULD BEGIN TO IMPACT THE LOWER COAST BY 15Z.
TRAINING FROM NORTH TO SOUTH WITH RAINFALL RATES APPROACHING 3
IN/HR COULD CAUSE FLASH FLOODING IN A FEW LOCATIONS FROM THE LOWER
TO MIDDLE TEXAS COAST WITH 3-5 INCHES ANTICIPATED BY 15Z IN A
COUPLE OF LOCATIONS.

OTTO

ATTN...WFO...BRO...CRP...HGX...

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

LAT...LON   29209572 29139508 28789490 28449509 27769623
            26889684 25889696 25559733 25799783 26899808
            28069787 28889722 29189638