MESOSCALE PRECIPITATION DISCUSSION 0850
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
550 PM EDT SUN OCT 01 2017

AREAS AFFECTED...COASTAL EASTERN FLORIDA

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

VALID 012149Z - 020349Z

SUMMARY...BANDS OF HEAVY RAIN WILL CONTINUE TO STREAM INTO THE
ATLANTIC COAST OF FLORIDA. RAIN RATES UP TO 2 IN/HR MAY LEAD TO
LOCALIZED AREAS OF FLASH FLOODING WHERE BANDS CAN PERSIST.

DISCUSSION...KMLB AND KJAX RADARS SHOWED MULTIPLE SHALLOW HEAVY
RAIN BANDS ORGANIZING ALONG A QUASI-STATIONARY FRONT AND SEVERAL
ZONES OF ENHANCED LOW-LEVEL CONVERGENCE IN THE MOIST AND UNSTABLE
AIR MASS SOUTH OF THE FRONT. THE ATMOSPHERE IN THE AREA WAS
CHARACTERIZED BY DEEP TROPICAL MOISTURE WITH PRECIPITABLE WATER
VALUES AROUND 2.2 TO 2.3 INCHES (JAX 12Z SOUNDING, GPS PW
MEASUREMENTS, MODEL ANALYSIS). THE CONVECTIVE RAIN BANDS DID NOT
HAVE SIGNIFICANT DEPTH TO THEM...WITH MRMS ANALYZED 30 DBZ ECHO
TOPS GENERALLY BELOW 20,000 FEET. GIVEN THAT THIS IS LOWER THAN
THE -10C LEVEL...THIS IMPLIES VERY LITTLE ICE IN THESE CONVECTIVE
CLOUDS...DOMINANT WARM RAIN PROCESSES...AND EFFICIENT RAINFALL
PRODUCTION. MESONET OBSERVATIONS NEAR THE FLORIDA COAST FURTHER
CONFIRM THIS...WITH SOME OBSERVED HOURLY RAIN RATES UP TO 2 IN/HR
AND AROUND DOUBLE WHAT IS SUGGESTED BY RADAR IN SOME CASES.

MODELS DO SHOW THE BEST LOW-LEVEL MOISTURE CONVERGENCE SHIFTING
SOUTH WITH TIME AS SOME DRIER AIR BEGINS TO PUSH IN FROM THE
NORTHEAST. THEREFORE...THE MORE PROMINENT RAIN BANDS MAY BECOME
ESTABLISHED CLOSER TO THE SPACE COAST THIS EVENING OR OVERNIGHT.
THE ENVIRONMENT SOUTH OF THE FRONT IS EXPECTED TO REMAIN
RELATIVELY SIMILAR OVER THE NEXT 6 HOURS...SO ANY FOCUSED AREAS OF
LOW-LEVEL CONVERGENCE WOULD BE CAPABLE OF YIELDING A SHALLOW
TROPICAL RAIN BAND WITH RAIN RATES UP TO 2 IN/HR. AND FLOODING MAY
TEND TO DEVELOP MORE QUICKLY THAN SUGGESTED BY RADAR RAINFALL
ESTIMATES ALONE. THE GREATEST RISK SHOULD BE FOCUSED WITHIN 10-20
MILES OF THE COAST WHERE BOUNDARY LAYER CONVERGENCE WILL BE
MAXIMIZED.

LAMERS

ATTN...WFO...JAX...MLB...

ATTN...RFC...SERFC...

LAT...LON   29948190 29918148 29758122 29358097 29008081
            28698049 28278058 27898037 27578031 27778073
            28178110 28838161 29708209