MESOSCALE PRECIPITATION DISCUSSION 0269
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
401 AM EDT WED AUG 13 2014
 
AREAS AFFECTED...NORTHEASTERN NJ/SOUTHEASTERN NY/LONG
ISLAND/CT/RI/SOUTHERN MA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 130800Z - 131200Z
 
SUMMARY...TORRENTIAL DOWNPOURS CONTINUE TO IMPACT THE NJ COAST
EARLY THIS MORNING WITH HOURLY RAINFALL RATES REACHING THE 2-3"
RANGE. EXPECT THIS ACTIVITY TO CONTINUE LIFTING NORTH AND EAST
WITH THE HEAVY PRECIPITATION SPREADING INTO LONG ISLAND/CT/RI.
GIVEN THE HISTORY OF THIS SYSTEM...FLASH FLOODING WILL BE LIKELY
THROUGH AT LEAST 12Z.  

DISCUSSION...THIS AXIS OF CONVECTION CONTINUES TO REMAIN
LOW-TOPPED GIVEN THE GENERAL LACK OF LIGHTNING BEING OBSERVED IN
THE PAST FEW HOURS. HOWEVER...HIGHLY EFFICIENT WARM RAIN PROCESSES
HAVE DOMINATED AND BROUGHT TORRENTIAL RAINFALL FROM THE BALTIMORE
MD AREA NORTHEASTWARD THROUGH NORTHERN DE AND INTO
SOUTHERN/EASTERN NJ. MOST RECENTLY THE MESONET OBSERVATIONS
DEPICTED HOURLY RAINFALL AS HIGH AS 3.06" IN SHARK RIVER HILL...NJ
WITH 5.57" OF RAIN OBSERVED IN BEACHWOOD...NJ BETWEEN 04-06Z. IT
APPEARS AN AREA OF LOW PRESSURE DEVELOPING ALONG THE AXIS OF
LOW-LEVEL CONVERGENCE HAS HELPED LOCALLY ENHANCE VERTICAL MOTIONS
OVER THESE AREAS.

LOOKING AHEAD...THE 06Z RAP FORECAST STILL SHOWS ANOMALOUS PWATS
BEING ADVECTED NORTH-NORTHWESTWARD TOWARD LONG ISLAND VIA A ROBUST
35 TO 40 KNOT SOUTH-SOUTHEASTERLY 850-MB JET. DYNAMICS REMAIN
STRONG AND SEEM TO BE MAKING UP FOR THE LACK OF INSTABILITY.
MUCAPE VALUES FROM THE 06Z RAP OBJECTIVE ANALYSIS ARE ONLY AROUND
200-300 J/KG. THE HIGH-RESOLUTION MODELS DOING BEST WITH THE
CONVECTION ARE THE 06Z HRRR AND 00Z NSSL-WRF. WHILE SLIGHTLY OFF
IN TIMING...BOTH DEPICT HEAVY RAINFALL CONTINUING WITH THE LATTER
MODEL FOCUSING THE ACTIVITY ACROSS MUCH OF LONG ISLAND AND INTO
WEST-CENTRAL CT. CONFIDENCE REMAINS HIGH THIS COMPLEX WILL REMAIN
INTACT THE NEXT FEW HOURS WHILE MORE UNCERTAIN THEREAFTER.


RUBIN-OSTER

ATTN...WFO...BOX...OKX...ALY...

ATTN...RFC...MARFC...NERFC...

LAT...LON   41687341 41957288 42017168 41797100 41307081 41107123
            40947170 40637249 40427290 40207336 40637393 41057391
            41687341