MESOSCALE PRECIPITATION DISCUSSION 0605
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
449 AM EDT MON JUL 31 2017

AREAS AFFECTED...WEST CENTRAL FLORIDA

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

VALID 310848Z - 311448Z

SUMMARY...A DEEP SURGE OF TROPICAL MOISTURE OVER WESTERN FLORIDA
IN ASSOCIATION WITH A SURFACE LOW NEAR THE COAST IS EXPECTED TO
RESULT IN WIDESPREAD HEAVY SHOWERS AND THUNDERSTORMS.  THE
POTENTIAL EXISTS FOR SOME RAINFALL AMOUNTS IN EXCESS OF 4 INCHES
BY 11AM LOCAL TIME.

DISCUSSION...RADAR AND SURFACE OBSERVATIONS ARE INDICATING A WELL
DEFINED CIRCULATION ABOUT 100 MILES WEST OF THE GREATER TAMPA BAY
AREA EARLY MONDAY MORNING.  HEAVY CONVECTION WITH THIS LOW HAS
GRADUALLY BEEN INCREASING IN COVERAGE OVER THE PAST COUPLE OF
HOURS, WITH NEAR TERM MODEL GUIDANCE SUGGESTING THAT THIS TREND
WILL CONTINUE.

ATMOSPHERIC PARAMETERS ARE QUITE CONDUCIVE FOR HEAVY RAINFALL
ACROSS THE WESTERN FLORIDA PENINSULA DURING THE MORNING HOURS. 
RIGHT ENTRANCE UPPER LEVEL JET DYNAMICS ARE ALLOWING FOR DEEP
LAYER ASCENT TO THE EAST OF THE LOW.  LOW LEVEL MOISTURE FLUX
ANOMALIES APPROACHING 3 STANDARD DEVIATIONS FROM THE SOUTHWEST,
INCLUDING CONVERGENT 850MB FLOW NEAR THE COAST AND FRICTIONAL
CONVERGENCE WITH LAND, WILL FURTHERMORE RESULT IN ENHANCED ASCENT
AND WIDESPREAD CONVECTION.  THE MAIN MITIGATING FACTOR HERE IS THE
RELATIVELY HIGH FLASH FLOOD GUIDANCE VALUES INITIALLY, WHICH KEEPS
THIS FROM OTHERWISE BEING A FLASH FLOOD LIKELY SCENARIO. 
URBANIZED AREAS HAVE A GREATER RISK OF FLOODING CONCERNS.

RECENT HI-RES MODEL RUNS ARE RATHER OMINOUS WITH THE PROJECTED
RAINFALL THROUGH 15Z, WITH THE LATEST HRRR SHOWING THE POTENTIAL
FOR 6 INCHES OF RAIN BETWEEN TAMPA AND FORT MYERS!  THE
EXPERIMENTAL HRRR ALSO HAS SIMILAR AMOUNTS BUT SLIGHTLY LESS IN
THE WAY OF COVERAGE.  OTHER NEAR TERM GUIDANCE, INCLUDING THE ARW
AND NMMB, ARE IN THE 3 TO 6 INCH RANGE.  IF THESE MODEL SOLUTIONS
VERIFY, THESE TYPES OF AMOUNTS WILL BE ENOUGH TO CAUSE SOME
FLOODING PROBLEMS.

D. HAMRICK

ATTN...WFO...MFL...MLB...TBW...

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

LAT...LON   28528223 28258166 27528125 26928092 26458079
            25928090 25618116 25688171 26378225 27108266
            27838301 28408274