

705 

AGNT40 KWNM 100115

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

915 PM EDT TUE AUG 9 2016



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

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



THE PRELIM 00Z NCEP-OPC SFC ANALYSIS INDICATED A WEAK STNRY FRONT

EXTENDING FROM NEAR CAPE HATTERAS E AND SE OVR CENTRAL NT2 WTRS.

HIGH PRES WAS LOCATED NR GEORGES BANK DRIFTING SE. OVERALL...PER

THE LATEST OBS AND 18Z MDL GUID IT APPEARS AS IF LITTLE CHANGE

WILL BE NEEDED TO THE PREV FCST FOR THE EVE UPDATE. THE LATEST

LIGHTNING DENSITY INDICATED ONLY A FEW ISOLATED TSTMS NR THE FRONT

THIS EVE...WITH NO MAJOR CHANGES EXPECTED FROM THE PREV FCST.



SEAS...SEA HEIGHTS RANGE FROM NR 4-5 FT OVR SRN NT2 WTRS TO

GENERALLY 3 FT OR LESS ELSEWHERE...PER THE LATEST OBS...ALTIMETER

DATA...AND 00Z RA1 SEA STATE ANALYSIS GRAPHIC. OVERALL...NO MAJOR

CHANGES APPEAR NECESSARY FOR THE EVE UPDATE FROM THE PREV FEW OPC

FCSTS.



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

PREVIOUS DISCUSSION...



THE LTST GOES WV IMGRY INDC A SHORTWAVE TROF OVER FAR SE

CANADA...WITH THE TAIL END EXTENDING SW TO JUST E OF THE OFSHR

WTRS. THE IMGRY ALSO INDC AN UPR RDG MOVG INTO THE ERN CONUS...AND

THE LTST NCEP SFC ANALYS INDC HIGH PRES BUILDING OVER THE N

PORTION OF THE OFSHR WTRS...WITH A STNRY FRONT ACRS THE S PORTION

ASSOC WITH THE SHORTWAVE TROF. THE LGTNG DENSITY PROD INDC

ISOLATED SHOWERS AND TSTMS ALONG THE FRONT EARLIER...BUT WITH THE

FRONT WKNG AND HIGH PRES BUILDING OVER THE AREA...CONVECTION HAS

DIED DOWN. IN ADDITION...THE VIS IMGRY INDC A BROAD AREA OF LOW

PRES OVER THE NE GULFMEX AND FLORIDA PANHANDLE...WITH SOME OF THE

MOISTURE AND INSTABILITY ADVECTING INTO THE FAR SW NT2 WATERS.

THE PREV FCST HAD MENTIONED A CHANCE OF SHOWERS AND TSTMS...SO

PLANNING ON CONTG WITH THAT. HOWEVER...WL DCRS THE CHANCE TO

SLIGHT INTO WED...AS THE 15Z SREF GUID INDC CHC OF CNVTN WL DCRS

WITH THE LOW IN THE NE GULF DRIFTING W.



ALSO...THE CRNT SFC DATA INDC WINDS MAINLY IN THE 5 TO 10 KT RANGE

IN NT2...AND ASCAT WIND RETRIEVALS FM 14Z INDC ABT THE SAME WITH A

FEW POCKETS TO 15 KT NR THE AFOREMENTIONED WKNG FRONTAL BNDRY. THE

12Z GFS/ECMWF WINDS ARE INIT OK WHEN COMPARED WITH THE DATA AND

INDC THE WINDS WL RMN IN THE 5 TO 15 KT RANGE OVER THE OFSHR

WATERS IN THE OFSHR WTRS OVER THE NEXT 24 HOURS AS HIGH PRES

BUILDS OVER THE W ATLC....AND THE REST OF THE 12Z MODELS AGREE

WELL WITH THE GFS AND ECMWF. THE GFS/ECMWF HAVE BEEN CONSISTENT

WITH THIS SOLN...SO CONFDC IS FAIRLY HIGH WITH THE GUID IN THE

SHORT RANGE. 



THE 12Z GFS AGREES VERY WELL WITH THE 12Z ECMWF THRUT THE

REMAINDER OF THE FCST PD ON THE OVERALL PTTN...ESP WITH THE TMG

OF A FRONTAL BNDRY THRU NT1 WED NGT INTO THU. THE GFS HAD BEEN

SLIGHTLY FASTER THAN THE ECMWF IN PREV RUNS...BUT NOW AGREES WELL.

THE 12Z GEM AND UKMET ARE SLIGHTLY SLOWER...SO ALL 12Z SOLNS IN

RSNBL AGRMT ON THIS FEATURE. HOWEVER...ATTM A LTL CONCERNED ON THE

INTNSTY OF THE GFS WINDS...WHICH ARE A LTL STGR THAN THE

UKMET/ECMWF IN THE SW FLOW OVER THE COLD SHELF WATERS IN NT1. AS A

RESULT...PLANNING ON A COMPROMISE SOLN...AND WL BLEND THE

GFS/ECMWF SFC WINDS N OF THE GULF STREAM TO ACCT FOR THE HIGHER

GFS WINDS. THIS SITUATION CONT WITH ANOTHER FRONT THAT MOVES OFF

THE NEW ENGLAND COAST FRI...AND MOVES INTO NT1 FRI AND SAT. WL

CONT WITH THE SAME BLEND TO DAMPEN GFS WINDS SLIGHTLY IN NT1 AHD

OF THIS NEXT BNDRY. OTRW WL USE THE 12Z GFS FOR THE REMAINDER OF

THE FCST...WITH MDT TO HIGH CONFDC AS IT WELL SUPPORTED BY THE

REST OF THE 12Z GLBL MODELS. 



SEAS...THE 12Z ECWMF WAM AND WAVEWATCH-III MODELS ARE INIT WITHIN

A FT OF THE CRNT DATA...WHICH IS CRNTLY 5 FT OR LESS OVER THE W

ATLC UNDER HIGH PRES BUILDING OVER THE W ATLC. THE MODELS AGREE

WELL THRUT THE FCST PD...SO PLANNING ON USING A 50/50 BLEND OF THE

TWO SOLNS AS COMPROMISE TO MINOR 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.

