MESOSCALE PRECIPITATION DISCUSSION 0799
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
430 PM EDT SUN SEP 10 2017

AREAS AFFECTED...EAST-CENTRAL...NORTHEAST FL...SOUTHEAST GA

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

VALID 102030Z - 110230Z

SUMMARY...WELL ORGANIZED CONVECTIVE BANDS ASSOCIATED WITH
HURRICANE IRMA WILL CONTINUE TO ADVANCE INLAND FROM THE ATLANTIC
OCEAN AND CONCENTRATED INLAND. INCREASINGLY SIGNIFICANT RUNOFF
AND/OR FLASH FLOODING IS LIKELY.

DISCUSSION...THE LATEST RADAR IMAGERY SHOWS A SIGNIFICANT ARRAY OF
CONVECTIVE BANDS ADVANCING INLAND OFF THE ATLANTIC OCEAN WELL
NORTHEAST OF THE CENTER OF HURRICANE IRMA. THE CONVECTION IS
PRODUCING EXTREMELY HEAVY RAINFALL RATES OF CLOSE TO 3
INCHES/HR...AND IS BEING FACILITATED BY VERY STRONG LOW LEVEL
FORCING/CONVERGENCE ALONG THE COAST AND JUST INLAND. MORE
SPECIFICALLY...A COMBINATION OF SPEED AND FRICTIONAL CONVERGENCE
ALONG WITH SIGNIFICANT MOISTURE AND INSTABILITY TRANSPORT IS
AIDING THE ORGANIZED NATURE OF THESE CONVECTIVE BANDS WITHIN A
STRONGLY SHEARED ENVIRONMENT.

BASED ON THE LATEST RAP ANALYSIS AND SURFACE OBSERVATIONS...THERE
IS ALSO A QUASI-STATIONARY FRONTAL ZONE DRAPED ACROSS THE
NORTH-CENTRAL PART OF THE STATE...WITH A SW/NE ORIENTATION FROM
NORTH OF TAMPA NORTHEAST TO NEAR ST. AUGUSTINE. THIS VERY STRONG
ATLANTIC INFLOW WILL CONTINUE TO INTERACT WITH THIS FRONTAL ZONE
AND PROVIDE A DEGREE OF STRONG ISENTROPIC ASCENT FOR AREAS NORTH
AND WEST OF THIS BOUNDARY...RESULTING IN PERSISTENT HEAVY
RAINFALL. AS IRMA LIFTS NORTH UP ALONG OR JUST INLAND OF THE WEST
COAST OF THE PENINSULA...THIS FRONT SHOULD BEGIN TO ADVANCE
FARTHER NORTHWEST WHICH WILL ALLOW IN TIME HEAVIER RAINFALL TO
SPREAD FARTHER NORTH.

THE HEAVIEST RAINFALL THOUGH THROUGH THIS PERIOD SHOULD BE
CONFINED WITHIN THE STRONG CONVECTIVE BANDS IMPACTING THE
EAST-CENTRAL TO NORTHEAST PART OF FL AND IN TIME BECOMING MORE
FOCUSED OVER SOUTHEAST GA. ADDITIONAL RAINFALL TOTALS OF 4 TO 6+
INCHES ARE EXPECTED...WITH SIGNIFICANT RUNOFF AND/OR FLASH
FLOODING CONCERNS EXPECTED.

ORRISON

ATTN...WFO...CHS...JAX...MLB...TBW...

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

LAT...LON   31868129 31548102 30728124 29468098 28388058
            28048080 27998129 28228185 29128218 30108241
            31358213 31808172