

115 

AGNT40 KWNM 251327

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN 

NWS OCEAN PREDICTION CENTER WASHINGTON DC

930 AM EDT MON 25 JUL 2016 



.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT 

.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N. 



LATEST LIGHTNING DENSITY PRODUCT IS SUGGESTING THAT CONVECTION 

JUST LOCATED ABOUT 30 TO 90 NM E OF CAPE MAY IS WEAKENING 

SOMEWHAT AS IT MOVES ESE AT ABOUT 35 KT. HOWEVER THERE ARE 

LIKELY AT LEAST GALE FORCE GUSTS INVOF THESE STRONGER TSTMS. 

LATEST HRRR AND 4KM NAM ARE INDICATING THAT WEAKENING TREND 

SHOULD CONTINUE OVER NEXT FEW HOURS. 06Z GFS WAS MOSTLY 

CONSISTENT WITH ITS PREVIOUS RUN AND CONTINUED TO BE MORE 

PROGRESSIVE THAN ECMWF/ UKMET/CMC WITH A DEVELOPING SURFACE LOW 

MOVING OFF THE MID ATLC COAST LATE IN THE FORECAST PERIOD. MADE 

SOME CHANGES TO SHORT TERM WX GRIDS TO ACCOUNT FOR ABOVE 

MENTIONED CONVECTION... OTHERWISE WILL NOT BE MAKING SIGNIFICANT 

ADJUSTMENTS TO PREVIOUS OPC GRIDS OR OFFSHORE FORECASTS.



---------------------------------------------------------------

...PREVIOUS DISCUSSION...



OVER THE SHORT TERM...THE NEW 00Z MDLS OVERALL SHARE SMLR FCST 

TIMING FOR A WEAK COLD FRONT TO APPROACH FM THE NW TODAY...PUSH 

SE ACROSS THE NT1 WTRS LATE TONITE/TUE...AND THEN INTO THE NRN 

NT2 WTRS TUE NITE. THE MDLS CONT TO FCST THE STRONGEST ASCD 

WINDS (GNRLY UP TO 15-20 KT...OR 25 KT AT MOST) WITH THIS FROPA 

TO DVLP IN THE SWLY PREFRONTAL GRADIENT TO ACRS THE NRN/CNTRL 

NT2 WTRS TONITE/TUE. THEREFORE AS WAS DONE FOR THE PREVIOUS 

OFSHR FCST PACKAGE...PLAN ON POPULATING OUR FCST WIND GRIDS WITH 

THE REPRESENTATIVE 00Z GFS 10M BL WINDS FOR TODAY THRU TUE NITE 

WHICH WL RESULT IN MINIMAL CHNGS. 



IN THE LONG RANGE...THE 00Z MDLS IN GNRL AGREE THAT THE COLD 

FRONT WL BCM QSTNRY ACRS THE NRN/CNTRL NT2 WTRS WED INTO THU NITE

WITH PRHPS A WEAK SFC LOW(S?) TRACKING NE ALONG THE FRONT WITH 

ASCD GRADIENTS REMAINING WEAK (WITH MAX ASCD WINDS GNRLY IN THE 

15-20 KT RANGE). FURTHER N THE 00Z GLOBAL MDLS WITH SLIGHT 

TIMING DIFFERENCES NOW FCST A WEAK COLD FRONT TO MOV OFSHR INTO 

THE NT1 WTRS THU NITE...THEN WEAKEN FRI. WITH THE MDLS STIL 

FCSTG WEAK ASCD WINDS...THE 00Z GFS 10M BL WINDS STIL LOOK TO BE 

REPRESENTATIVE AND HENCE WL CONT TO POPULATE WITH THESE WINDS ON 

WED THRU THU NITE. 



BY LATE FRI INTO FRI NITE THE DISPARITY INCREASES BTWN THE 00Z 

GLOBAL MDLS. WHL THE OTHER GLOBAL MDLS FCST THE QSTNRY FRONT TO 

WASH OUT...THE 00Z GFS FCSTS THE FRONT TO PERSIST WITH A MR SIG 

SFC LOW THAN ITS PREV RESPECTIVE RUNS FCST TO MOVE OFF THE MID 

ATLC COAST ON THE FRONT FRI NITE. THE 00Z GEFS MEAN INDICATES 

THAT THE 00Z GFS IS LKLY SMWHT TOO STRONG WITH THIS FRONTAL LOW 

AND ALSO TOO FAR S. THEREFORE SINCE THEIR SOLUTION IS CLOSER TO 

THE LATEST WPC MEDIUM RANGE GUIDANCE AND AS A COMPROMISE...WL 

TRANSITION TO POPULATING WITH A 50/50 BLEND OF THE 00Z ECMWF AND 

00Z UKMET BL WINDS FOR FRI/FRI NITE. 



.SEAS...OVERALL THE 00Z WAVEWATCH III AND 00Z ECMWF WAM MDLS HV 

BOTH INITIALIZED THE CURRENT SEAS VERY WELL (GNRLY WITHIN ONE FT 

VS THE LATEST SFC OBS). WITH THE 00Z GFS BEING FAVORED...PLAN ON 

POPULATING OUR FCST WAVE GRIDS WITH ALL 00Z WAVEWATCH III FOR 

TODAY THRU THU NITE...WHICH OVERALL ARE NOT SIGLY DIFFERENT THAN 

THE 00Z ECMWF WAM FCST SEAS. THEN SINCE THE 00Z ECMWF WL BCM 

FAVORED...WL THEN TRANSITION TO POPULATING WITH ALL 00Z ECMWF 

WAM FCST SEAS FOR FRI/FRI NITE. 



.EXTRATROPICAL STORM SURGE GUIDANCE...N/A. 



.WARNINGS...PRELIMINARY. 



.NT1 NEW ENGLAND WATERS... 

     NONE. 



.NT2 MID ATLC WATERS... 

     NONE. 



$$ 



.FORECASTER CLARK/VUKITS. OCEAN PREDICTION CENTER.

