

041 

AGNT40 KWNM 240008

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

808 PM EDT TUE AUG 23 2016



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

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



UPDATE...18Z NCEP SFC ANALYSIS SHOWS A LARGE HIGH PRES RIDGE

BUILDING E OVER THE OFSHR WTRS...WITH A COLD FRONT WELL E OF THE

OFSHR ZONES TRANSITIONSING INTO A STATIONARY FRONT IN THE WTRS

BETWEEN THE NT2 AREA AND BERMUDA. LATEST AVAILABLE ASCAT AND ASCAT

HI-RES PASSES FROM THIS MORNING SHOW WINDS TO 20 KT IN NE FLOW

OVER THE SRN NT2 ZONES AND OVER THE INNER ZONES NEAR CAPE

HATTERAS...BUT ELSEWHERE IN THE OFSHR WTRS INDICATES ONLY LIGHT

WINDS OF 15 KT OR LESS. LIGHTNING DENSITY PRODUCT DATA AT 2300Z

SHOWS A FEW AREAS OF SCATTERED SHOWERS AND TSTMS JUST S OF THE NT2

AREA...BUT NO ACTIVITY OVER THE OFSHR WTRS.



MAIN WEATHER FEATURES...THE WEAK SUMMERTIME PATTERN IS EXPCTD TO

CONTINTUE THRU THE FCST PERIOD...WITH WINDS NOT EXPCTD TO EXCEED

25 KT. A RIDGE WILL PASS SLOWLY E OVER THE OFSHR WTRS WED INTO

FRI. A COLD FRONT WILL APPROACH THE COAST FROM THE NW FRI...THEN

MOVE SE OVER THE OFSHR WTRS FRI NITE INTO SAT NITE WHILE

WEAKENING. ANOTHER RIDGE WILL BUILD SE OVER THE OFSHR WTRS LATE

SAT INTO SUN...THEN PERSIST SUN NITE.



MODELS...THE MED RNG MDLS ARE IN VERY GUD OVERALL AGREEMNT ACROSS

THE OFSHR WTRS THRU THE FCST PERIOD...EXCEPT THE GEM TAKES THE

REMNANTS OF FIONA NW INTO THE SRN NT2 WTRS ON SUN WHICH LOOKS

ANOMALOUS. THE GFS 10M SOLN LOOKS REPRESENTATIVE ENUF TO BE USED

FOR THE WIND GRIDS THRU AT LEAST SUN NITE. AM NOT PLANNING TO MAKE

ANY SIGNIF CHANGES TO THE CURRENT FCST TREND.



SEAS...THE WNA WAVEWATCH III AND ECMWF WAM BOTH INITIALIZED WELL

OVER THE OFSHR WTRS VERSUS THE RA1 SEA STATE ANALYSIS. THE MDLS

BOTH LOOK REASONABLE AND STAY WITHIN 1 OR 2 FEET OF EACH OTHER

THRU THE ENTIRE FCST PERIOD PD...SO WILL USE A 50/50 BLEND OF THE

WNA WAVEWATCH III/ECMWF WAM FOR THE WAVE HT GRIDS AS A COMPROMISE

SOLN.



EXTRATROPICAL STORM SURGE GUIDANCE...N/A.



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

PREVIOUS DISCUSSION...



THE LTST GOES VIS IMGRY INDC A FRNTL BNDRY JUST SE OF THE NT2

WATERS...AND THE LTNG DENSITY PROD INDC A FEW TSTMS NEAR THE

FRONT. THE PREV FCST HAD MENTION OF TSTMS AND SHOWERS IN SRN

NT2...SO PLANNING ON KEEPING IT FOR THE NEXT PKG. IN

ADDITION...THE 15Z ASCAT WIND RETRIEVALS INDC N TO NW WINDS OVR A

MAJORITY OF THE NT2 WTRS IN THE CAA BEHIND THE FRONT...AND ALSO

20 KT OVR THE GULF OF MAINE. CRNT BUOYS RPRT INDC SSTS NR 70 DEG

IN THE GULF OF MAINE...WHICH HAS LOWERED STATIC STABILITY IN THE

GULF OF MAINE AND ALLOWED DEEPER VERT MIXING THE CAA.

HOWEVER...THE LTST NCEP SFC ANALYS INDC THE FRONT AND STGST CAA

HAS MOVED WELL E OF THE AREA...AND CRNT SFC RPRTS INDC WINDS TO

15 KT OVR NT1. THE 12Z GFS INDC 15 KT AT 18Z IN FAR ERN NT1 AND

NE NT2...AND IS INIT WELL OVER THE GULF OF MAINE IN THE CAA...AND

OVER THE REMAINDER OF THE W ATLC WHEN COMPARED WITH THE CRNT DATA.

THE ASCAT ALSO INDC 5 TO 10 KT OVER GEORGES BANK AND S OF NEW

ENGLAND...INDCG A HIGH PRES RDG BUILDING OVR THE AREA FROM THE W.

THE 12Z MDLS ALL INDC THE WINDS WL CONT TO DCRS AS THE FRONT

MOVES OFF THE E AND HIGH PRES BUILDS OVER THE REGION. THE PREV

FCST FLWD THE GFS IN THE SHORT TERM...WHICH STILL LOOKS GUD...SO

PLANNING ON FAVORING THE 12Z GFS IN THE SHORT TERM.



OTRW...THE 12Z MDLS AGREE FAIRLY WELL THRUT THE FCST PD...AND INDC

THE HIGH PRES RDG CRNTLY BUILDING OVER THE AREA WL BE THE

PREDOMINANT WX FEATURE INTO THU NGT. THE 12Z GFS/ECMWF/UKMET ALL

INDC ANOTHER WK COLD FRONT WL MOVE INTO NT1 FRI INTO SAT...AND

AGREE ON THE TMG AND INTNSTY OF THE FRONT. THE 12Z GEM CONT TO BE

A PROGRESSIVE OUTLIER...SO PREFERRING TO STAY AWAY FM THAT SOLN

ATTM. IN ADDITION...THE 12Z MDLS DIFFER SOME ON THE REMNANT LOW OF

FIONA TO THE S OF NT2 IN THE EXTENDED PD...WITH THE 12Z GFS

REMAINING A LTL STGR THAN THE 12Z ECMWF/UKMET. HOWEVER...ALL SOLNS

KEEP THE LOW S OF THE AREA...SO NOT XPCTG IT TO IMPACT NT2. OTRW

THE 12Z GFS HAS SHOWN GUD RUN TO RUN CONSISTENTCY ON THE OVERALL

PTTN THRUT THE FCST PD...AND IS WELL SUPPORTED BY THE 12Z

ECMWF/UKMET SOLNS ON SYNOP FEATURES...SO PLANNING ON USING IT IN

THE NEXT FCST PKG.



SEAS...THE 12Z WNA WAVEWATCH III AND ECMWF WAM ARE INITIALIZED

WELL OVER THE OFSHR WTRS...WHEN COMPARED WITH THE CRNT SFC DATA

AND RA1 WHICH INDC SEAS UP TO 5 FT IN THE OFSHR WATERS ATTM. THE

MDLS STAY WITHIN A CPL OF FEET OF EACH OTHER THRUT THE FCST

PD...AND SEEM RSNBL WITH KEEPING SEAS FAIRLY LIGHT UNDER THE XPCTD

BENIGN WX PTTN. ATTM PLANNING ON USING A 50/50 BLEND THRUT THE PD AS

A COMPROMISE TO THE MINOR DIFFS.



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



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER SCOVIL/KELLS. OCEAN PREDICTION CENTER.

