MESOSCALE PRECIPITATION DISCUSSION 0802
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1040 PM EDT SUN SEP 10 2017

AREAS AFFECTED...CENTRAL/NORTHERN FL...SOUTHEAST GA

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

VALID 110240Z - 110840Z

SUMMARY...HURRICANE IRMA CONTINUES TO ADVANCE NORTH UP ALONG THE
WEST SIDE OF THE FL PENINSULA WITH EXTREMELY HEAVY RAINFALL.
SIGNIFICANT RUNOFF AND/OR FLASH FLOODING IS EXPECTED OVERNIGHT.

DISCUSSION...HURRICANE IRMA AT 02Z/10PM EDT WAS LOCATED 50 MILES
ENE OF FT. MYERS FL...AND MOVING NORTH AT 14 MPH. THE INNER CORE
OF IRMA CONTINUES TO GRADUALLY WEAKEN OVER LAND AND THERE IS A
SIGNIFICANT AMOUNT OF DRY AIR POURING IN AROUND THE SOUTHERN
SEMICIRCLE OF THE STORM WHICH IS EVIDENCED QUITE STRONGLY FROM THE
SUITE OF NON-OPERATIONAL GOES-16 WV BANDS AND CONFIRMED BY RADAR
IMAGERY WHICH SHOWS LITTLE IF ANY CONVECTION SOUTH OF THE CENTER.

HOWEVER...VERY HEAVY RAINS CONTINUE TO FOCUS AROUND THE NORTHERN
SEMICIRCLE OF IRMA WITH ENHANCED SURFACE CONVERGENCE HELPING TO
SUSTAIN STRONGLY FORCED CONVECTION. THIS IS PARTICULARLY THE CASE
WITH THE REMNANTS OF THE NORTHERN EYEWALL STILL SEEN PRODUCING
SOME RAINFALL RATES OF 3 TO 4 INCHES/HR. MEANWHILE...VERY STRONG
ATLANTIC INFLOW WITH FOCUSED MOISTURE/INSTABILITY TRANSPORT IS
NOTED TOWARD THE EAST-CENTRAL AND NORTHEAST PART OF FL...AND THIS
IS FOSTERING SOME VERY INTENSE CONVECTIVE BANDS...WITH THE MOST
ORGANIZED BAND SITUATED FROM LAKE COUNTY EAST-SOUTHEAST ACROSS
SEMINOLE AND BREVARD COUNTIES. THIS CONVECTIVE BAND IS LIKELY
PRODUCING RAINFALL RATES OF CLOSE TO 4 INCHES/HR AND IS ALSO AT
LEAST BRIEFLY TRAINING OVER THE SAME AREA AS IT GRADUALLY LIFTS
NORTH WITH THE OVERALL FORWARD MOTION OF THE HURRICANE.

SURFACE OBSERVATIONS AND THE LATEST RAP ANALYSIS ALSO CONTINUE TO
SHOW A FRONTAL ZONE DRAPED ACROSS THE NORTH-CENTRAL PART OF THE
STATE...WITH A SW/NE ORIENTATION FROM NEAR TAMPA NORTHEAST TO NEAR
ST. AUGUSTINE. THIS VERY STRONG ATLANTIC INFLOW WILL CONTINUE TO
INTERACT WITH THIS FRONTAL ZONE AND PROVIDE A DEGREE OF VERY
STRONG ISENTROPIC ASCENT FOR AREAS NORTH AND WEST OF THIS
BOUNDARY...RESULTING IN PERSISTENT HEAVY RAINFALL WELL NORTH AHEAD
OF IRMA. AS IRMA LIFTS NORTH ACROSS WEST-CENTRAL FL...THIS FRONT
SHOULD BEGIN TO ADVANCE FARTHER NORTHWEST WHICH WILL ALLOW FOR
HEAVIER RAINFALL TO SPREAD FARTHER NORTH INTO ADJACENT AREAS OF
SOUTHERN GA LATER IN THE NIGHT.

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 AS MUCH
AS 4 TO 8+ INCHES ARE EXPECTED THROUGH DAWN. ELSEWHERE ACROSS
CENTRAL AND NORTHERN FL...ADDITIONAL RAINFALL AMOUNTS OF 3 TO 6
INCHES ARE EXPECTED AND ESPECIALLY NEAR THE CENTER OF IRMA.
SIGNIFICANT RUNOFF AND/OR FLASH FLOODING CONCERNS ARE EXPECTED
WITH THESE TOTALS.

ORRISON

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

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

LAT...LON   31478112 30728124 29468098 29148078 28248060
            27658076 27278109 27428165 27458259 27838296
            28698277 29148298 29388330 30298315 31278209