MESOSCALE PRECIPITATION DISCUSSION 0735
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 AM EDT SAT AUG 26 2017

AREAS AFFECTED...MIDDLE TO UPPER TX COAST

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

VALID 260639Z - 261215Z

SUMMARY...FLASH FLOODING...SOME OF WHICH COULD BE HIGHLY
SIGNIFICANT...IS EXPECTED ACROSS PORTIONS OF THE UPPER TEXAS COAST
THROUGH 12Z WITH 6 HOUR RAINFALL TOTALS BETWEEN 4-8 INCHES
EXPECTED. A SECONDARY MAX IS EXPECTED NEAR THE CENTER OF HURRICANE
HARVEY.

DISCUSSION...HURRICANE HARVEY WAS LOCATED ABOUT 5 MILES NORTH OF
ROCKPORT TEXAS ACCORDING TO THE NATIONAL HURRICANE CENTER AT 06Z
AND WAS MOVING TO THE NW AT 5 KT. DESPITE SOME
WARMING...EXPERIMENTAL GOES 16 INFRARED IMAGERY CONTINUED TO SHOW
A CONTINUOUS RING OF -65 C CLOUD TOPS SURROUNDING THE EYE OF
HARVEY. WHILE SOME FURTHER WEAKENING OF RAIN RATES WITHIN THE
EYEWALL IS POSSIBLE AS THE EYE CONTINUES TO MOVE INLAND...THE SLOW
MOVEMENT OF THE CURRENT 1-2 IN/HR RATES LOCATED IN THE FRONT LEFT
AND FRONT RIGHT SECTIONS OF THE EYEWALL WILL EXTEND FLASH FLOODING
INTO GOLIAD AND VICTORIA COUNTIES THROUGH 12Z.

FARTHER UP THE TEXAS COAST...REPEATING CELLS OVER BRAZORIA AND
FORT BEND COUNTIES HAVE LED TO DUAL POL RAINFALL ESTIMATES OF 6-9
INCHES THROUGH 06Z. WHILE TEMPORARY WEAKENING OF THIS AREA HAS
BEEN NOTED IN FAVOR OF A NEW SPIRAL BAND INTO MATAGORDA COUNTY...A
RESERVOIR OF GREATER INSTABILITY SOUTH OF A STATIONARY FRONT ALONG
THE UPPER TEXAS COAST WILL CONTINUE TO SUPPORT STRONG ISENTROPIC
LIFT AND REPEATING CELL MOTIONS AT TIMES FROM THE EASTERN EYEWALL
OF HARVEY TO THE SABINE RIVER.

THE LATEST HI-RES MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE
IDEA OF THE HEAVIEST 6 HOUR RAINFALL TOTALS INTO THE UPPER TEXAS
COAST...FOCUSING JUST NORTH AND WEST OF GALVESTON BAY. HALF OF THE
SUITE OF HI-RES MODELS AVAILABLE AT WPC SHOW 8-10 INCHES THROUGH
12Z...WHICH MAY BE OVERDONE...BUT THE PROXIMITY OF THIS AREA TO
THE HOUSTON METRO IS CONCERNING. TRAINING AXES OF RAINFALL RATES
BETWEEN 2-3 IN/HR ARE EXPECTED TO GENERATE A SIGNIFICANT FLASH
FLOOD THREAT FOR PORTIONS OF THE UPPER TEXAS COAST EXTENDING PAST
SUNRISE.

OTTO

ATTN...WFO...CRP...EWX...HGX...LCH...

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

LAT...LON   30779506 30549425 30039372 29359390 28409559
            27549669 27419737 27759790 28789823 29779774
            30399688 30709596