

045 

AGNT40 KWNM 260121

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN 

NWS OCEAN PREDICTION CENTER WASHINGTON DC

925 PM EDT THU 25 AUG 2016 



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

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



GULF OF MAINE BUOYS HAVE BEEN REPORTING IN THE 15 TO 20 KT RANGE 

FOR THE BETTER PART OF THE DAY TODAY WHILE ELEVATED MT DESERT 

ROCK AND MATINICUS ROCK HAVE REPORTED 20 TO 25 KT. OVER THE NEAR 

TERM THE PREVIOUS OPC WIND GRIDS MAY BE SHOWING TOO EXPANSIVE OF 

AN AREA TO 20 KT HERE BUT OTHERWISE LOOK REASONABLE. TONED DOWN 

THE HIGHER WIND GRIDS SLIGHLY OVER GULF OF MAINE/GEORGES BANK 

FOR TONIGHT AND FRI. THE LATEST MODELS APPEAR TO HAVE ARRIVED AT 

A BETTER CONSENSUS WITH THE TIMING OF THE WEAK COLD FRONT ACROSS 

THE NT1 AND NRN/CENTRAL NT2 WATERS FRI NIGHT INTO SAT NIGHT. THE 

PREVIOUSLY TIME SHIFTED 12Z GFS THEN STILL LOOKS GOOD FOR TIMING 

OF NEXT COLD FRONT MON NIGHT THROUGH TUE NIGHT. 



BUOY 44065 S OF WRN LONG ISLAND SUGGESTING THAT WAVE HEIGHTS 

ACROSS S OF NEW ENGLAND WATERS ARE 1 TO 2 FT OR SO HIGHER THAN 

BOTH THE 12Z/18Z WAVEWATCH III AND 12Z ECMWF WAM. WAVEWATCH III 

MOVES THE LONG PERIOD SWELL ASSOCIATED WITH GASTON INTO THE ERN 

MOST NT2 OFFSHORE WATERS SAT EVENING THEN NEW ENGLAND COAST SUN 

AND MID ATLC COAST LATER SUN AND SUN NIGHT...WHICH IS ABOUT 12 

TO 18 HOURS FASTER THAN THE ECMWF WAM. AT THIS TIME AM LEANING 

TOWARD THE WW3 SOLUTION.     



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

...PREVIOUS DISCUSSION...



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 CLARK/KELLS. OCEAN PREDICTION CENTER.

