

943 

AGNT40 KWNM 191223

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

823 AM EDT FRI AUG 19 2016



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

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



UPDATE...06Z NCEP SFC ANALYSIS SHOWS A WEAK LOW CENTERED OVER THE

NE PART OF THE NT2 AREA...WITH AN ASSOCD TROF EXTNDG SW FROM THE

LOW ACROSS THE NRN NT2 WTRS TO THE VIRGINIA CAPES AREA. THE

ANALYSIS ALSO INDICATES A COLD FRONT MOVING S INTO THE GULF OF

MAINE. LATEST AVAILABLE ASCAT AND ASCAT HI-RES PASSES FROM LAST

NITE SHOW WINDS TO 20 KT IN SW FLOW OVER THE CENTRAL AND SRN NT2

WTRS...BUT OTHERWISE INDICATE LIGHT WINDS OF 15 KT OR LESS.

LIGHTNING DENSITY PRODUCT DATA AT 1110Z SHOWS AREAS OF SCATTERED

SHOWERS AND TSTMS OVER THE NT2 WTRS S OF THE LOW AND TROF NOTED

FROM THE SFC ANALYSIS.



MAIN WEATHER FEATURES...A COLD FRONT WILL MOVE SE OVER THE NT1 AND

NRN NT2 WTRS TODAY...STALL ACROSS THE CENTRAL NT2 WTRS TONITE AND

SAT...THEN LIFT N AS A WARM FRONT SAT NITE THRU SUN NITE. ANOTHER

COLD FRONT WILL APPROACH THE COAST FROM THE NW SUN...MOVE OFSHR 

SUN NITE...THEN SWEEP SE OVER THE OFSHR WTRS MON INTO MON NITE.



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

THE OFSHR WTRS DURING THE FCST PERIOD...EXCEPT THE GEM IS TOO

SLOW WITH THE COLD FRONT ON MON THRU TUE. THE GFS 10M SOLN LOOKS

REPRESENTATIVE ENUF TO BE USED FOR WIND GRIDS OVER THE ENTIRE

FCST PERIOD. AM NOT PLANNING TO MAKE ANY SIGNIFICANT CHANGES TO

THE CURRENT FCST TREND.



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

OVER THE OFSHR WTRS...AND THESE MDLS ARE IN GUD AGREEMNT THRU THE

FCST PERIOD WITH ONLY MINOR DIFFERENCES NOTED AT VARIOUS TIMES.

WILL USE A 50/50 BLEND OF THE WNA WAVEWATCH III MDL AND THE ECMWF

WAM TO SMOOTH OUT THE DIFFERENCES. 



EXTRATROPICAL STORM SURGE GUIDANCE...N/A.



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

PREVIOUS DISCUSSION...



THE 01Z AND 0240Z ASCAT WIND RETRIEVALS INDC SW UP TO 20 KT AHD

OF A FRONTAL BNDRY ACRS NRN NT2...AND CRNT SFC RPRTS INDC ABT THE

SAME. 00Z GFS WINDS ARE INIT OK WHEN COMPARED WITH THE CRNT

DATA...AND INDC THE WINDS WL CONT AT 20 KT EARLY TODAY...AS A WK 

LOW PRES CENTER OVER NRN NT2 MOVES E THROUGH THE N PORTION ALONG

THE FRONT. THE 00Z GFS AGREES WELL WITH THE 00Z ECMWF/UKMET/GEM/NAM

ON THE TMG AND INTNSTY OF THE FRONT...AND INDC THE LOW WL MOVE E

OF THE AREA BY THIS AFTN. THE GFS HAS BEEN A LTL SLOWER ON THE

LOW WHEN COMPARED WITH THE REST OF THE 00Z GUID...BUT HAS TRENDED

A LTL FASTER FM THE 18Z RUN. THE PREV FCST WENT WITH THE GFS ON

THIS FEATURE...SO ATTM PLANNING ON STAYING CLOSE TO IT AS WELL

SINCE THE GFS HAS SHOWN GUD RUN TO RUN CONSISTENCY AND AGREES

FAIRLY WELL WITH THE REST OF THE 00Z GUID...MAINLY ON THE INTNSTY

OF THE WINDS.



IN ADDITION...CRNT SFC RPRTS SHIFTED FM SW TO N OVER THE GULF OF

MAINE BETWEEN 03Z AND 06Z...WITH WINDS UP TO 15 KT AHEAD OF

A WK BNDRY OVER THE GULF OF MAINE. EARLIER RUNS OF THE GFS HAD

BEEN A LTL STGR THAN THE REST OF THE GUID WITH THE SW FLOW...BUT

HAS TRENDED A LTL WKR WITH THE 00Z RUN...AND IS NOW IN DECENT

AGRMT WITH THE 00Z MDLS WITH THE WINDS AND THE TMG OF THE BNDRY. 

THE GFS INDC IT WL MOV E THRU THE AREA TDA...SO PLANNING ON FLWG

THE GFS WITH THIS FEATURE...AND WL USE THE 10M WINDS.



THE 00Z GFS INDC ANTHR FRONT WL MOVE INTO NT1 AND NRN NT2 SUN NGT

INTO MON. THE GFS HAS BEEN SLIGHTLY FASTER THAN THE

ECMWF/UKMET/GEM WITH THE TMG OF THE FRONT...THO HAS TRENDED A LTL

SLOWER WITH THE 00Z AND IS NOW IN GUD AGRMT WITH THE 00Z

ECMWF/UKMET SOLNS ON THE TMG. THE MDLS AHD BEEN A LTL OVERDONE

WITH THE SW WINDS AHD OF THE FRONT OVR THE GULF OF MAINE...AND HAD

INDC 25 KT. THIS SEEMS A LTL HIGH CONSIDERING THE STABLE

ENVIRONMENT OVER THE SHELF WATERS...AND 925 MB WINDS ONLY SHOW UP

TO ABT 30 KT...SO VERT SHEAR DOES NOT SEEM IT WL HELP WITH PUCHING

THROUGH THE STABLE PBL. ATTM PLANNING ON CAPPING WINDS AT 20 KT IN

THE SW FLOW AHD OF THE FRONT. HOWEVER...THE 00Z MDLS INDC A FAIR

AMT OF CAA ON THE OTHER SIDE OF THE FRONT...WHICH WL LOWER

STATIC STABILITY SOME. THE 00Z GFS/ECMWF/UKMET ALL INDC SMALL

AREAS OF 25 KT WINDS...SO CONFDC IS MDT TO HIGH THAT THE WINDS WL

REACH THAT INTNSTY. OTRW THE 00Z GFS AGREES WELL WITH THE 00Z

ECMWF/UKMET THRUT THE REMAINDER OF THE FCST PD...SO PLANNING ON

STAYING WITH IT FOR THE REMAINDER OF THE FCST PD.



.SEAS...THE 06Z RA1 INDC WV HTS UP TO 5 FT IN THE OFSHR WTRS...AND

THE 00Z WAVEWATCH-III AND ECMWF WAM MODELS ARE INIT WIHTIN A FT OF

THE CRNT DATA. THE MDLS AGREE FAIRLY WELL THRUT THE FCST PD...SO

PLANNING ON USING A 50/50 BLEND OF THE TWO SOLNS.



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



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER SCOVIL/KELLS. OCEAN PREDICTION CENTER.

