

606 

AGNT40 KWNM 270121

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

921 PM EDT TUE JUL 26 2016



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

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



NO MAJOR CHANGES TO THE ONGOING OPC FCST APPEAR NEEDED FOR THE EVE

UPDATE. WE WILL ONLY TWEAK GRIDS SLIGHTLY TO FIT CONDITIONS NOTED

JUST PRIOR TO FCST ISSUANCE AND ALSO TWEAK THEM SLIGHTLY TO FIT

NEARBY COASTAL WTRS AND TAFB FCSTS A LITTLE BETTER. THE 00Z PRELIM

SFC ANALYSIS SHOWS A WEAK COLD FRONT MOVG FROM NT1 INTO NRN NT2

WTRS...WITH A WEAK LOW PRES TROF TRAILING THE FRONT JUST OFF THE

NEW ENGLAND COAST. THE 18Z GFS IS CONSISTENT OVR THE SHORT TERM

WITH THE 12Z CYCLE. THE FRONT IS FCST TO STALL OVR NRN AND CENTRAL

NT2 WTRS WED AND WED NITE. THE LATEST RADAR...SATELLITE...AND

LIGHTNING DENSITY IMAGERY INDICATES WEAKENING SCTD TSTMS MOVG E-SE

OFF THE COAST JUST N OF CAPE HAT...WITH ADTL SCTD TSTMS WELL OFF

THE MID ATLC COAST...OVR OFF ZONE ANZ910. THE LATEST SREF TSTMS

GUIDANCE KEEPS THE HIGHEST CHANCES FOR TSTMS OVR NRN AND CENTRAL

NT2 WTRS THRU WED...AND THIS IS REFLECTED IN THE ONGOING FCST.



SEAS...SEA HEIGHTS RANGED FROM 1 TO 2 FT OVR THE GULF OF MAINE AND

FAR SW NT2 WTRS...TO 6 FT WELL OFF THE MID ATLC COAST OR NR ZONE

ANZ910 PER THE LATEST OBS AND ALTIMETER DATA. LITTLE CHANGE

APPEARS NECESSARY FOR THE EVE UPDATE. WE WILL MAKE A FEW MINOR

ADJUSTMENTS TO FIT THE PREV GRIDS WITH THE LATEST CONDITIONS AND

WITH NEARBY FCSTS...BUT OVERALL MAKE NO MAJOR CHANGE FOR THE EVE

UPDATE.



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

PREVIOUS DISCUSSION... 



THE 14Z AND 15Z ASCAT OVERPASSES RETURNED HIGHEST OFFSHORE WINDS 

TO 20 KT ACROSS THE GULF STREAM E OF 73W. 12Z MODELS WERE WELL 

INITIALIZED WITH THESE WINDS THIS MORNING...AND DO NOT OFFER 

MAJOR DIFFERENCES ACROSS THE W ATLC FOR THE NEXT FEW DAYS. A 

WEAK COLD FRONT CONTINUES TO SLOWLY APPROACH THE NEW ENGLAND AND 

NRN MID ATLC COASTS AND HAS NEARLY REACHED LONG ISLAND THIS 

AFTERNOON. AT 18Z A PREFRONTAL TROUGH ALSO STRETCHED SW ACROSS 

THE NRN NT2 WATERS TO NEAR CAPE CHARLES. THE 20 KT WINDS SEEN IN 

THIS MORNINGS ASCAT WERE S OF THIS FEATURE. 12Z MODELS ARE 

CONSISTENT IN SHOWING THE WEAK COLD FRONT WILL REACH THE NRN MID 

ATLC WATERS WED AND PERSIST INTO EARLY THU...BEFORE WASHING OUT 

THU NIGHT. GFS HAS BEEN MORE EMPHATIC ABOUT MAINTAINING THE WEAK 

QUASI STATIONARY BOUNDARY. FOR WIND GRIDS WILL CONTINUE TO USE 

THE 12Z GFS THROUGH WED NIGHT. LATER IN THE WEEK THE GFS HAS 

BEEN CONSISTENTLY MORE PROGRESSIVE THAN THE ECMWF/UKMET/CMC WITH 

A DEVELOPING SURFACE LOW TO MOVE OFF THE NRN MID ATLC COAST AND 

THROUGH THE SRN NT1 WATERS LATE FRI INTO SAT. 12Z GEFS OFFERS 

BETTER SUPPORT FOR THE SLOWER ECMWF/UKMET...AND ALSO SUGGESTS 

THAT THE GFS MAY BE TOO WEAK WITH LOW. VERSUS ITS 00Z RUN THE 

12Z ECMWF WAS SLIGHTLY STRONGER AND MORE IN LINE WITH ITS 12Z 

RUN YESTERDAY. 12Z UKMET ALSO TRENDED STRONGER. BASED ON THIS 

PLAN AM FAVORING THE 12Z ECMWF THU THROUGH THE WEEKEND...AND 

LIKE WAS DONE PREVIOUSLY WILL ADJUST THESE S TO SW WINDS HIGHER 

BY ABOUT 10 PERCENT FRI NIGHT INTO SAT OVER THE OUTER NT2 WATERS 

N OF HATTERAS CANYON ACROSS THE GULF STREAM. THIS WILL RESULT IN 

INTRODUCING SOME 30 KT WINDS FOR A BRIEF PERIOD ACROSS ANZ920 

AND ANZ910 ZONES. 12Z ECMWF AND 12Z UKMET CONTINUE IN GOOD 

AGREEMENT THAT COLD FRONT ASSOCIATED WITH FRI/SAT LOW WILL STALL 

NEAR THE DELMARVA SAT NIGHT...AND REMAIN NEARLY STATIONARY 

ACROSS THE NRN NT2 WATERS SUN/SUN NIGHT AS WEAK LOW PRES MOVES E 

ALONG THE FRONT. 12Z MODELS ARE MOSTLY CONSISTENT THAT WINDS TO 

20 OR 25 KT S OF THE FRONT SHOULD PERSIST THROUGH SUN NIGHT.   



SEAS...THE 12Z WAVEWATCH III AND 12Z ECMWF WAM ARE ABOUT 1 FT 

TOO HIGH WITH WAVE HEIGHTS ACROSS THE NT1 WATERS BUT ELSEWHERE 

ARE WELL INITIALIZED THIS AFTERNOON...AND ARE IN GOOD AGREEEMENT 

THROUGH THU. TO BE CONSISTENT WITH WINDS WILL POPULATE WITH THE 

12Z WW3 THROUGH WED NIGHT...THEN SWITCH TO THE 12Z ECMWF WAM THU 

THROUGH SUN NIGHT. 



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





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER MILLS/CLARK. OCEAN PREDICTION CENTER.

