

210 

AGNT40 KWNM 251935

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

335 PM EDT THU AUG 25 2016



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

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



GOES WV IMGRY INDC A SOMEWHAT FLAT RIDGE OVER THE WRN ATLC AND A

SHORTWAVE TROF UPSTREAM MOVING INTO THE GREAT LAKE REGION. THE LTST

NCEP SFC ANALYS INDC A HIGH PRES RDG ACRS THE OFSHR WTRS UNDER THE

UPR RDG...A WK STNRY FRNTL BNDRY JUST E OF THE AREA NR

BERMUDA...AND A COLD FRONT INLAND OVER THE GREAT LAKES REGION

ASSOC WITH THE SHORTWAVE TROF MOVING E TWD NT1. 15Z ASCAT INDC

VARIABLE WINDS 5 TO 15 KT OVR THE N PTTN UNDER THE RIDGE...EXCEPT

OVER THE GULF OF MAINE WHERE THE ASCAT INDC SRLY WINDS TO 20 KT

AHD OF A WK LOW PRES TROF NEAR THE COAST. THE ASCAT ALSO INDC NE

FLOW OVR SRN NT1 TO THE W OF THE STNRY FRONT E OF THE AREA. CRNT

SFC RPRTS INDC WINDS TO 15 KT OVR NT1...AND THE 12Z GFS WINDS

WHICH ARE WELL INITIALIZED WHEN COMPARED WITH THE CRNT DATA INDC

THE INTNSTY OF WINDS ARE SLOWLY DECREASING AS THE STNRY FRONT AND

RIDGE ARE BOTH SLOWLY WEAKENING. THE 12Z ECMWF/NAM/GEM/UKMET ALL

INDC THE SAME TREND...SO ATTM PLANNING ON REFLECTING MDL TRENDS

AND WL SLWOLY DCRS THE WINDS IN SRN NT2 TNGT. ALSO...THE 12Z

ECWMF/NAM/GEM/UKMET AGREE SOMEWHAT WELL WITH THE GFS ON THE TMG

OF THE COLD FRONT CRNTLY OVER THE GREAT LAKES REGION...BUT THE

NAM/GEM/GFS ARE A BIT STGR WTIH THE SW WINDS AHD OF THE

FRONT...RANGING BTWN 25 AND 30 KT. THE 12Z ECMWF AND UKMET ARE

WKR...AND INDC ONLY 15 TO 20 KT. BUOY REPORTS CRNTLY INDC SSTS IN

THE MID 60S TO 70 DEG F IN THE GULF OF MAINE...AND THE 12Z GFS

STABILITY INDICES INDC THAT THE NORMALLY STABLE ENVIRONMENT OVER

THE COLD SHELF WATERS IN THE GULF OF MAINE IS NOT QUITE AS STABLE

AS USUAL WITH THE WARMER SSTS IN PLACE. HOWEVER...WITH THE GFS

INDCG ONLY ABT 25 TO 30 KT IN SW FLOW AT 925 MB...THE VERT

SHEAR LOOKING LIMITED...AND MODEL STABILITY INDICES INDICATING

ONLY MARGINAL INSTABILITY...AM THINKING THAT 25 KT AND HIGHER SFC

WINDS ARE OVERDONE. AS A RESULT...PLANNING ON CAPPING WINDS AT 20

KT IN THE NEXT PKG.



OTRW...THE 12Z GFS INDC HIGH PRES WL BUILD OVER THE AREA ON SAT

AND SUN AFTER THE WK CD FRONT MOVES E OF THE REGION. THE 12Z MDLS

HAVE BEEN IN SOMEWHAT DECENT AGRMT ON ANOTHER WK FRONT MOVG INTO

NT1 MON...WITH SOME DIFFS ON THE TMG. THE 12Z ECMWF HAS TRENDED

SLIGHTLY FASTER FM THE 00Z...AND IS NOW A LTL FASTER THAN THE

CONSISTENT 12Z GFS. THE 12Z GEM HAS TRENDED TWD THE GFS...BUT THE

12Z UKMET IS THE PROGRESSIVE SOLN...SO THERE IS A FAIR AMT OF

UNCERTAINTY ON THE TMG. THE PREV FCST FAVORED THE GFS...SO

PLANNING ON FAVORING IT IN THE NEXT FCST...BUT PLANNING ON TIME

SHIFTING IT TO MAKE IT A LTL FASTER IN DEFERENCE TO THE

UKMET/ECMWF SOLNS.  HOWEVER...THE 06Z GFS HAS NOT CHANGED MUCH FM

THE PREV RUN...WHICH WAS USED IN THE PREV FCST...SO ATTM PLANNING

ON STAYING WITH CONTINUITY FOR THE REMAINDER OF THE FCST PD.



SEAS...THE 12Z WAVEWATCH AND ECMWF WAM MDLS HAVE BOTH INITIALIZED

WELL OVER THE OFSHR WTRS WHEN COMPARED WITH THE RA1 SEA STATE

ANALYSIS AND SFC RPRTS. THE MDLS BOTH LOOK REASONABLE IN THE SHORT

RANGE... AND GENERALLY STAY WITHIN 1 TO 2 FEET OF EACH OTHER THRU

THE SHORT TERM...SO WILL FAVOR THE 12Z WW3 AS IT REFLECTS THE

TRENDS OF THE PREFERRED GFS SOLN. HOWEVER...WL TIME SHIFT SEAS A

LTL FASTER MON TO REMAIN CONSISTENT WITH THE PREVIOUSLY MENTIONED

WIND TIME SHIFT.



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



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER KELLS. OCEAN PREDICTION CENTER.

