

163 

AGNT40 KWNM 180704

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

304 AM EDT THU AUG 18 2016



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

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



THE LTST GOES IR SATELLITE IMAGERY AND LTST NCEP SFC ANALYS INDC

DVLPG LOW PRES SE OF NOVA SCOTIA...WITH A FRONTAL BNDRY EXTENDING

TO THE SW THROUGH NRN NT2. THE LGTNG DENSITY PROD INDC SHOWERS AND

TSTMS ALONG THE FRONT...MAINLY IN THE UNSTABLE ENVIRONMENT OVER

THE GULF STREAM. THE PREV FCST INDC SHOWERS AND TSTMS CONSISTENT

WITH THE CRNT CONDITIONS...SO PLANNING ON MAINTAINING WX GRIDS.

OTRW CRNT SFC RPRTS INDC WINDS TO 20 KT IN THE SW FLOW AHD OF THE

FRONT...AND 5 TO 10 KT N OF THE FRONT. THE 0215 UTC ASCAT WIND

RETRIEVALS INDC 20 INVOF THE FRONT OVER NT2...AND A FEW 25 KT JUST

E OF THE WATERS. THE 00Z GFS WINDS ARE INIT OK WHEN COMPARED WTIH

THE CRNT DATA...AND INDC THE WINDS WL DCRS AS THE SYS MOVES

QUICKLY OFF TO THE E. THE 00Z ECWMF/UKMET/GEM/NAM ALL AGREE FAIRLY

WELL WITH THE GFS ON THE TMG OF THE FRONTAL BNDRY...AND ON THE

INTNSTY OF THE WINDS. THE PREV FCST STARTED OFF WITH 25 KT...BUT

THE DATA INDC CONDITIONS ARE A LTL WKR ATTM...SO PLANNING ON

STARTING OFF WITH 20 KT...AS INDC BY THE 00Z GFS. ALSO PLANNING ON

STAYING WITH THE GFS IN THE SHORT TERM ON THIS FEATURE...AS IT IS

INIT OK AND IS CONSISTENT WITH PREV RUNS...AND AGREES WITH REST OF

00Z MODELS...SO CONFDC IS MDT TO HIGH IN THE SHORT TERM WITH THE

GFS.



THE 00Z GFS AGREES FAIRLY WELL WITH THE 12Z ECMWF THRUT THE

REMAINDER OF THE FCST PD ON THE SYNOP PTTN...AND INDC A WKR CD

FRONT WL MOVE INTO NT1 TNGT INTO FRI. THE 00Z MDLS ALSO INDC A LOW

WL FORM ALONG THE FIRST FRONT OVR NT2 TNGT...AND MOVE OFF TO THE

E. THE 00Z ECMWF IS SLIGHTLY FASTER THAN THE GFS WITH THE

LOW...BUT IS IN SOMEWHAT RSNBL AGRMT ON THE TWO FEATURES. THE 00Z

UKMET/GEM AGREE WELL WITH THE 00Z ECMWF ON THE LOW...SO PREFERRING

IT ATTM WITH IT.



IN THE EXTENDED...THE 00Z GFS INDC THE FIRST FRONTAL BNDRY WL

DRIFT INTO NT2 WHILE WKNG INTO SAT...BEFORE ANOTHER FRONT MOVES

INTO THE W ATLC LATE SUN NIGHT INTO MON NIGHT. THE GFS HAS BEEN

CONSISTENT ON THE TMG AND INTSTY OF THE FRONT...AND INDC THE WINDS

WL NOT INCRS TO MORE THAN 25 KT IN THE SRLY FLOW OVR NT1. THIS

SEEMS SLIGHTLY HIGHER...AS THE COLD SHELF WATERS WL MODIFY THE AIR

MASS ABOVE IT AND INCRS STATIC STABILITY...PREVENTING STGR WINDS

ALOFT FROM MIXING DN TO THE SFC. AS A RESULT...PLANNING ON STAYING

WITH THE 00Z ECWMF IN THE EXTENDED...AS IT SEEMS A BIT MORE RSBL

WITH THE INTNSTY OF THE WINDS. HOWEVER...THE GFS AGREES WITH THE

REST OF THE 00Z MODELS ON THE TMG OF THE FRONT...SO CONFDC IS MDT

WITH THE 00Z ECMWF AS IT IS SUPPORTED BY MOST 00Z SOLNS. 



.SEAS...06Z RA1 INDC THE HIGHEST SEAS...UP TO 11 FT...ASSOC WITH

THE STG WIND ALONG THE AFOREMENTIONED FRNTL BNDRY HAVE MOVED E OF

THE OFSHR WTRS...SEAS GENLY 8 FT OR LESS OVER THE OFSHR WTRS. THE

00Z NWW3 AND ECWMF WAM ARE INIT WELL WHEN COMPARED WITH THE CRNT

DATA...AND INDC THE SEAS WL CONT TO SUBSIDE OVR THE NEXT 24 HOURS

AS THE STGST WINDS CONT TO MOVE E OF THE AREA. THE 00Z MDLS REMAIN

WITHIN A FT OR TWO OF EACH OTHER THRUT THE FCST PD...UNDER THE

RELATIVELY BENIGN WX PTTN. AS A RESULT...PLANNING ON USING A

50/50 BLEND OF THE TWO MDLS AS A COMPROMISE SOLN.



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



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER KELLS. OCEAN PREDICTION CENTER.

