MESOSCALE PRECIPITATION DISCUSSION 0229
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
837 PM EDT TUE JUN 16 2015
 
AREAS AFFECTED...WESTERN GULF COAST....SOUTHEAST TX... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 170036Z - 170606Z
 
SUMMARY...AN INNER BAND OF HEAVY RAINFALL HAS DEVELOPED JUST TO
THE EAST OF THE CIRCULATION CENTER OF TROPICAL STORM BILL. THIS
PARTICULAR BAND HAS A HISTORY OF DROPPING NEARLY 2 INCHES OF RAIN
IN AN HOUR. GIVEN THIS BANDING SIGNATURE...FLASH FLOODING WILL BE
LIKELY.  

DISCUSSION...AS OF 00Z...TROPICAL STORM BILL HAS WOBBLED TOWARD
THE NORTHEAST RELATIVE TO ITS PREVIOUSLY ANALYZED POSITION IN MPD
#0226. WHILE THE OUTER BAND HAS WEAKENED IN RECENT HOURS...THE
INNER BAND HAS BECOME MUCH MORE ORGANIZED STRETCHING FROM JUST
NORTHEAST OF THE CIRCULATION CENTER DOWN TO THE OFFSHORE WATERS OF
THE TX COAST. MESONET DATA SHOWS AROUND 2 INCHES IN AN HOUR
INCLUDING OVER 4 INCHES IN ONLY A 3-HOUR PERIOD. NEARBY
OBSERVATIONS SUPPORT SUCH RAINFALL RATES WHICH SIGNIFICANTLY
EXCEEDS LOCAL FFG VALUES. AS A RESULT...FLASH FLOODING WILL BE
LIKELY...PARTICULARLY AS LONG AS A DEFINED MESOSCALE BAND
CONTINUES TO MAINTAIN ITS STRENGTH. AT THIS TIME...THE 12Z
HRW-ARW/HRW-ARW-PARALLEL RUNS SHOW THIS BANDING FEATURE QUITE WELL
AND MAINTAIN IT THROUGH 06Z. 

RECENT WATER VAPOR IMAGERY SHOWS A BIT OF DRY AIR TRYING TO WORK
ITS WAY INTO THE SOUTHWESTERN SIDE OF BILL. THIS HAS HELPED FOCUS
MUCH OF THE CONVECTION ON THE EASTERN HALF OF THE CIRCULATION.
WHERE IT IS CURRENTLY PRECIPITATING...THE TROPOSPHERE IS QUITE
MOIST WITH PWATS IN THE 2.25 TO 2.50 INCH RANGE WHICH SUGGESTS
VERY EFFICIENT HEAVY RAINFALL PROCESSES.

CONVECTION-ALLOWING MODELS SHOW SOME VARIABILITY IN THE AXIS OF
HEAVY RAINFALL WHICH APPEARS TO BE DRIVEN BY DIFFERENCES IN THE
PLACEMENT OF THE TROPICAL CIRCULATION. THE SIGNAL IS EVIDENT
ACROSS THE BOARD WHICH IS SUPPORTED BY RECENT RADAR/SATELLITE
TRENDS. THROUGHOUT THE NIGHT...FFG VALUES SHOULD LOWER AS HEAVY
RAIN CONTINUES TO FALL. CONSEQUENTLY...THIS SHOULD ENHANCE THE
THREAT FOR FLASH FLOODING ACROSS MUCH OF THE REGION WELL INTO THE
OVERNIGHT HOURS.


RUBIN-OSTER

ATTN...WFO...BRO...CRP...EWX...FWD...HGX...LCH...

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

LAT...LON   31249590 30929492 30509437 29409373 28309342 
            27369366 26729470 26439648 26539768 27229786 
            27769736 27999720 28499710 28779743 29129778 
            29739817 30679803 31119708