MESOSCALE PRECIPITATION DISCUSSION 0615
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
855 AM EDT WED AUG 02 2017

AREAS AFFECTED...WESTERN FL PENINSULA

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

VALID 021255Z - 021800Z

SUMMARY...MULTIPLE BOUTS OF HIGHLY EFFICIENT RAINFALL MAY POSE
FLOODING CONCERN.  POTENTIAL FOR THUNDERSTORMS NEAR FLOODED ZONES
SOUTH OF  TAMPA BAY.

DISCUSSION...EXPERIMENTAL GOES-16 VISIBLE LOOP DEPICTS A CLOSED
SURFACE WAVE JUST WEST OF CEDAR KEY.  WHILE ONSHORE STATIONS
DEPICT TYPICAL MORNING PRESSURE RISES...BOUYS OFFSHORE INDICATE
ONLY MINOR RISES OR NEAR STEADY CONDITIONS SUGGESTING EARLY
CONVECTIVE ROUND SUPPORTED FURTHER STRENGTHENING OF THE LOW.  AS
SUCH ORIENTATION OF EFFECTIVE TROPICAL WARM CONVEYOR ON THE
SOUTH/SOUTHEAST PERIPHERY IS STRONGER THAN EXPECTED SUPPORTING
INCREASED MOISTURE FLUX AND INCREASED FRICTIONAL SURFACE
CONVERGENCE IN/ALONG THE COASTAL REGION.  12Z RAOBS IN JAX/TBW
ALSO SHOW NEARLY SATURATED PROFILES BELOW 5H WITHIN THE
CONVEYOR...MATCHING CIRA LAYERED PW TRENDS/MAGNITUDES TO SUPPORT
TPWS OVER 2.25".  GIVEN DEEP WARM CLOUD PROCESSES RAINFALL RATES
IN EXCESS OF 2.5"/HR ARE LIKELY WITH EXTREME RATES OVER 3-4"/HR
POSSIBLE.

GIVEN THE STRONG SFC CONVERGENCE AND INSTABILITY WELL LOCATED
OFFSHORE (SBCAPES AT ABOVE 3500 J/KG)... RECENT NEW CONVECTIVE
DEVELOPMENT OFF SHORE CITRUS/HERNANDO COUNTIES PER VISIBLE/10.3UM
IR SHOWING RAPID COOLING...WHICH EXTENDS FURTHER UPSTREAM ALONG
THE CONVEYOR TOWARD A SECONDARY DEVELOPING INFLECTION NEAR
27.9N86.1W.  THE ORIENTATION AND STRENGTH OF FLOW A LIKELY TO
SUPPORT FAVORED ORIENTATION AND BACKBUILDING TO ALLOW FOR MULTIPLE
BOUTS OF THESE HIGHLY EFFICIENT THUNDERSTORMS.  AS SUCH THERE IS
POTENTIAL PARTICULARLY ALONG CITRUS/HERNANDO COUNTIES TO HAVE 4-5"
TOTALS WITH ISOLATED THREAT OVER 6" IN THE NEXT 6HRS NOT OUT OF
THE QUESTION.  LIMITING FACTOR IS THE TRADITIONAL ABILITY OF THIS
AREA TO ABSORB THESE TYPES OF RATES AS FFG VALUES ARE ABOVE 3 TO
4" IN 1HR TO 3HR RESPECTFULLY...ESPECIALLY THE AREAS REMAINS
RELATIVELY DRY PER AHPS 7-14 DAY ANOMALY PLOTS.  STILL THE
MAGNITUDE WARRANTS AT LEAST A POSSIBLE THREAT FOR FLOODING
CONDITIONS BY 18Z.

SOUTH OF TAMPA BAY...CURRENT ORIENTATION TO THE NARROW WARM
CONVEYOR PLACES LIMITED CONCERN ACROSS AREAS CURRENTLY
EXPERIENCING FLOODING PER AHPS.  HOWEVER...THERE DOES REMAIN SOME
PERIPHERAL SOUTHWESTERLY ONSHORE FLOW FOR MODEST MST CONVERGENCE.
HOWEVER INSTABILITY IS MUCH MORE LIMITED IN THIS AREA (EVEN MORE
SO THAN FURTHER NORTH).  CONCERN HERE IS RECENT VISIBLE IMAGERY
SUGGEST THE CLOUD EDGE MAY ALLOW FOR CLEAR ENOUGH SKIES FOR
INCREASING SOLAR INSOLATION THROUGH THE EARLY MORNING.  IF
SUFFICIENT CONVECTION IS LIKELY TO STILL BE RELATIVELY EFFICIENT.

OF GREATER CONCERN...THE CLOUD EDGE MAY ALLOW FOR SW-NE ORIENTED
DIFFERENTIAL HEATING BOUNDARY THAT IS ALIGNED WITH MEAN CLOUD
BEARING FLOW SUGGESTIVE OF TRAINING OF ANY CELLS THAT WOULD
DEVELOP.  THE THREAT FOR FLASH FLOODING IS ONLY CONSIDERED
POSSIBLE HERE AS THERE IS STILL MODERATE REDUCTION IN CONFIDENCE
ON CONVECTIVE INITIATION...BUT IF IT DOES THE THREAT FOR ENHANCED
FLOODING/FLASH FLOODING CONDITIONS MAY BE IMMEDIATE. 

GALLINA

ATTN...WFO...JAX...TAE...TBW...

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

LAT...LON   29838314 29448209 28468206 27778171 26948236
            27288285 27818309 28258294 28688289 28968311
            29278336 29668347