MESOSCALE PRECIPITATION DISCUSSION 0074
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1118 AM EDT SUN MAY 10 2015
 
AREAS AFFECTED...THE COASTAL PLAIN OF NC 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 101516Z - 102116Z
 
SUMMARY...RAINFALL RATES ARE BEGINNING TO INCREASE IN ASSOCIATION
WITH TROPICAL STORM ANA, EXPECTED TO MOVE THROUGH THE NC COASTAL
PLAIN.  WITH AN EMERGING SIGNAL FOR HEAVY RAINFALL IN THE
MESOSCALE GUIDANCE, FLASH FLOODING IS CONSIDERED POSSIBLE.

DISCUSSION...ANA REMAINS A TROPICAL STORM LATE THIS MORNING PER
THE 15Z ADVISORY FROM NHC.  OVERNIGHT, RAINFALL TOTALS WERE
MODEST, WITH THE HIGHEST AMOUNT NOTED IN SOUTHWEST CARTARET COUNTY
(ALONG THEIR BARRIER ISLAND) OF 2.53".  HOWEVER, RECENT RADAR
TRENDS INDICATE AN UPTICK TO CONVECTIVE COVERAGE, WITH 2-3 SPIRAL
BANDS SHOWING UP EAST OF ITS CENTER IN RECENT SCANS.  PRECIPITABLE
WATER VALUES ARE 1.75-2", PAR FOR THE COURSE FOR A SYSTEM OF
NON-TROPICAL ORIGIN.  WINDS AT 850 HPA/NEAR THE CLOUD BASE ARE
BROADLY 25-40 KTS ALONG THE NC COAST, DOUBLE THE MEAN 850-400 HPA
WIND, WHICH SHOULD SET UP PRECIPITATION EFFICIENCY.  MIXED LAYER
CAPE VALUES NEAR THE OUTERMOST BAND ARE 1000-2000 J/KG, SUFFICIENT
FOR WET MULTI-CELLS.  

OFFSHORE, CAPE VALUES REMAIN 1000-2000 J/KG, WHICH SHOULD BE ABLE
TO ADVECT IN AS FAR THE ANA'S EXPECTED TRACK.  THE 00Z SPC WRF,
00Z WRF4NSSL, AND 06Z NAM CONEST APPEAR TOO HIGH WITH RAINFALL
AMOUNTS NEAR THE SYSTEM'S CENTER -- DUE TO THE CAPE/INFLOW
ORIENTATION, A MORE PROLONGED/MODEST RAIN EVENT IS EXPECTED NEAR
ITS CORE MORE TYPICAL OF A FLOOD RATHER THAN A FLASH FLOOD EVENT. 
HOWEVER, WITHIN THE SPIRAL BANDS, WITH GREATER INFLOW AND
INSTABILITY, THE MESOSCALE GUIDANCE IS UNITED IN SUGGESTING 2-4"
OF RAIN POSSIBLE LOCALLY, NEAR THE REGION'S THREE HOURLY FLASH
FLOOD GUIDANCE.  AVAILABLE MOISTURE SUPPORTS RAIN RATES UP TO 2.5"
AN HOUR.  FLASH FLOODING IS CONSIDERED POSSIBLE.

ROTH

ATTN...WFO...ILM...MHX...RAH...

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

LAT...LON   36007558 35997557 35997557 35657539 35257544 
            35157549 35157549 35117562 35017593 34697635 
            34497651 34497652 34497652 34607675 34437735 
            34157774 33807791 33797794 33797794 33777837 
            33787850 33957889 34367893 34937837 35627689