

973 

AGNT40 KWNM 090127

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

927 PM EDT MON AUG 8 2016



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

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



THE PRELIM OPC-NCEP 00Z SFC ANALYSIS SHOWS A NEARLY STNRY FRONT

EXTENDING E FROM NR CAPE HATTERAS OVR CENTRAL NT2 WTRS. WEAK HIGH

PRES IS LOCATED N OF THE FRONT OVR FAR NRN NT2 WTRS. THE LATEST

SATELLITE IMGRY...RADAR...LIGHTNING DENSITY DATA INDICATES SCTD

TSTMS EXTENDING FROM NR CAPE HATTERAS E ALONG THE FRONT. A FEW

SHWRS WERE OCCURRING N OF THE FRONT OVR NRN NT2 WTRS. LOCALLY

GUSTY WINDS POSSIBLY NR GALE FORCE AND ROUGH SEAS CAN OCCUR IN OR

NEAR ANY OF THE HEAVIER TSTMS OVR MAINLY CENTRAL AND POSSIBLY SRN

NT2 WTRS OVR THE NEXT DAY OR SO. OVERALL...THE 18Z GFS IS SIMILAR

TO THE 12Z CYCLE WHICH WAS USED IN THE PREV FCST. FOR THE EVE

UPDATE WE SEE NO NEED TO MAKE MAJOR CHANGES TO THE ONGOING OPC

FCST.



SEAS...SEA HEIGHTS RANGE FROM 2 TO 3 FT OVR NW NT2 AND NT1 WTRS TO

4 TO 5 FT OVR CENTRAL INTO SRN NT2 WTRS PER THE LATEST OBS AND 00Z

RA1 SEA STATE ANALYSIS GRAPHIC. FOR THE EVE UPDATE WE DO NOT PLAN

ON MAKING SIG CHANGES TO THE PREV OPC FCST.



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

PREVIOUS DISCUSSION...



THE LTST GOES VIS IMGRY INDC A WK FRNTL BNDRY ACRS NT2. THE LGTNG

DENSITY PROD INDC SOME LIMITED CONVECTION ALONG THE FRONT...AND

THE PREV FCST INDC AN AREA OF SHOWERS AND TSTMS ALONG THE BNDRY.

THE 15Z SREF GUID INDC LIKELIHOOD OF TSTMS WL DCRS TUE. THE PREV

WX GRIDS HAD MENTION OF SCATTERED SHOWERS AND TSTMS GOING INTO

TUE...SO ATTM PLANNING ON LOWERING IT TO CHANCE OF.



OTRW..CRNT SFC RPRTS INDC SW WINDS TO 20 KT ALONG THE SE

COAST...IN THE WAA S OF THE AFOREMENTIONED FRONT. THE LTST NCEP

SFC ANALYS ALSO INDC A WK LOW OVR THE SE CONUS...AND THE 1440Z

ASCAT WIND RETRIEVALS INDC THE HIGHEST SFC WINDS ARE RIGHT ALONG

THE COAST CLOSEST TO THE LOW...WITH UP TO 25 KT ALONG THE SC

COAST. THE 12Z GFS IS INIT OK ON THE CRNT PTTN...ALTHO SLIGHTLY

LOW IN THE PREVIUOSLY MENTIONED AREA OFF THE SC COAST. THE MDL

INDC THE FRONT WL WKN TNGT INTO TUE AS HIGH PRES BUILDS OVR THE

NRN OFSHR WTRS. THE 12Z ECMWF/UKMET/NAM/GEM ALL AGREE WITH THE

GFS ON THE CRNT PTTN...AND ON THE FRONT WKNG OVER NT2. THE PREV

FCST WEAKENED THE WINDS TNGT INTO TUE IN RESPONSE TO HIGH PRES

BUILDING OVER THE AREA...WHICH IS CLOSE TO THE 12Z GFS. THIS

STILL SEEMS RSNBL...SO PLANNING ON STAYING WITH THE 12Z GFS IN

THE SHORT TERM.



ALSO IN THE VIS IMGRY..THE AREA OF CONVECTION ALONG A SFC TROF

JUST TO THE NE OF THE BAHAMAS DOES NOT LOOK QUITE AS IMPRESSIVE

AS YDA...AND THAT IS REFLECTED IN THE 12Z MODEL GUID. PREV RUNS OF

THE ECMWF/UKMET/GEM SOLNS FROM YDA INDC A WK LOW FORMING FROM THE

CONVECTION AND MOVG NE INTO SRN NT2 BY WED. HOWEVER...THE 00Z AND 

12Z RUNS FROM ALL 3 MDL SOLNS BACKED OFF ON THE LOW...AND NOW

ONLY INDC A WK TROF. THE GFS HAS BEEN CONSISTENT WITH SHOWING A

LOW...AND THAT SOLN HAS CONTINUED IN THE 12Z RUN. HOWEVER...THE

12Z GFS HAD BEEN A FAST OUTLIER WITH THE NEXT FRONTAL BNDRY MOVG

OFF THE NEW ENGLAND COAST WED NGT AND THU. THE 06Z GFS HAD TRENDED

SLOWER...AND WAS NOW CLOSE TO THE CONSENSUS OF THE 12Z GUID WITH

THE TMG OF THE FRONT. THE 12Z GFS TRENDED SLIGHTLY FASTER...AND IS

AGAIN SLIGHTLY FASTER THAN THE REST OF THE 12Z MDLS. ATTM WL BE 

FAVORING THE 12Z GFS SOLN IN THE EXTENDED...MAINLY FOR ITS

CONSISTENT SOLN WITH THE TROF FCST TO MOVE INTO NT2. HOWEVER...WL

BE TIME SHIFTING THE GFS 3 HOURS SLOWER...TO ACCOUNT FOR THE

FASTER TIMING OF THE FRONT OFF THE NEW ENGLAND COAST. 



.SEAS...THE 12Z WAVEWATCH III AND ECMWF WAM ARE BOTH WELL

INITIALIZED IN THE W ATLC...WITH SEAS CRNTLY UP TO 5 FT IN THE 

OFFSHORE WATERS. THIS MODLES ARE IN VERY GOOD AGREEMENT OVER THE

FORECAST PERIOD...SO WL BE USING A 50/50 BLEND OF THE TWO AS A

COMPROMISE TO THE SLIGHT DIFFS. 



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





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER MILLS/KELLS. OCEAN PREDICTION CENTER.

