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125
AGNT40 KWNM 171217
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
817 AM EDT THU APR 17 2014

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.

NO CHANGES ARE PLANNED FOR THE MORNING UPDATE. THE 06Z GFS WAS
VERY SIMILAR TO THE PREVIOUS 00Z RUN. THERE ARE NO BIG DIFFERENCES
IN THE MODELS THROUGH FRI AFTERNOON...HOWEVER BEYOND 00Z SAT THE
MODELS CONTINUE TO DIVERGE. STILL PREFER THE ECMWF FOR 00Z SAT AND
BEYOND AS IT LOOKS TO BE A DECENT COMPROMISE BETWEEN THE UKMET
WHICH IS SLOWER MOVING LOW NE INTO SRN NT2 WATERS AND THE FASTER
GFS WHICH SHIFTS THE LOW E FASTER. WILL ALSO MAINTAIN THE EXISTING
GALE WARNING ALREADY IN PLACE...THOUGH CONFDC IS LOW. THE LATEST
SEA STATE ANALYSIS INDICATED THAT THE MWW3 HAS A GOOD HANDLE ON
SEAS WITH OBSERVATIONS WITHIN A FT OF THE MODEL GUIDANCE.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

STLT TRENDS AND NEW 06Z NCEP SFC ANAL SHOW FNT JUST E OF MID ATLC
OFSHR WTRS CONTG TO SLOW DOWN WITH MUCH OF IT S OF HAT CNYN STNRY
WITH A WK FNTL WAVE FRMG OVR SRN PART. NEAR TERM GRADIENTS IN NE
FLOW NW OF FNT AS SHOWN IN MDLS APCH GALE FRC WITH INSTABILITY
HIGHEST AT THIS TIME...BUT TREND IS FOR AIRMASS TO MODIFY AND
CONDS BCM MORE STABLE WI 24 HR. EVENING ASCAT-A AND B IMAGERY
SHOWED WDSPRD NE 20 TO 30 KT ESPCLY SRN NT1 AREA SWD HIGHEST ALG
GLF STRMAND NE NT2...WHERE HI RES VERSION OF ASCAT-A EVEN HAD
SIME GALE BARBS IN FAR NE NT2 AREA WHERE GLF STRM LOOPS
NWD...BUT THAT WAS EARLY IN EVENING. ACCORDINGLY POPULATED 00Z
GFS THRU 00Z FRI WITH THE HIGHER 30M OR FIRST SIGMA LYR
WNDS...WHICH DO IN FACT GIVE WNDS APCHG GALE FRC.

OTRW MDLS CONT IN GOOD AGRMT THRU THU NIGHT AND INTO FRI...WITH
00Z GFS LOOKING RSNBL. GFS THEN CONTS TO MORE QUICKLY MOV LOW
PRES ALG FNT NE ACRS FL VERSUS OTHER MDLS...BUT BY SUN THE MDLS
ARE CLOSE IN PSN AS LOW SKIRTS SRN WTRS...BUT THEN GFS SPEEDS UP
VERSUS OTHER MDLS SUN NIGHT AND MON. 00Z ECMWF OVERALL IS MOST
CONSISTENT. BEYOND 18Z FRI USED 00Z ECMWF. RAISED ISSUE ABT PSBL
NE GALES EARLIER...AND GFS WITH ITS FASTER SOLN DVLPS THEM
EARLIER...SAT NIGHT VERSUS SUN IN ECMWF. 00Z GEM SPRTS ECMWF
WHILE 00Z UKMET WITH CLOSER TO CST TRACK IS LESS ROBUST.
THEREFORE WITH SOME CONFDC...LOW TO MDT...WILL INTRODUCE GALES
IN CENTRAL AND SRN NT2 ZONES SUN AS SPRTD BY ECMWF. GALES ARE
MOST LKLY AS FRESH CNDN HIGH BLDS OFF OF NEW ENGLAND AT THAT
TIME...INCRG GRADIENT...BUT AS HIGH MOVS OFF GRADIENT DMSHS
AFTER SUN.

SEAS...COMPARING MDLS WITH 06Z SEA STATE ANAL...00Z ECMWF WAM
APPRS BEST INITIALIZED OVR NT2 WTRS ESPCLY IN THE S...AND
THEREFORE POPULATED WITH THAT MDL THRU 00Z FRI AND AGAIN AFT 18Z
FRI WHEN ECMWF IS PREFERRED...BUT IN BETWEEN USED 00Z WNA MWW3.

.EXTRATROPICAL STORM SURGE GUIDANCE...00Z ETSS AND ESTOFS DVLP
SML POS SURGES GENLY 1 FT OR LESS...WITH ESTOFS SLGTLY
HIGHER...AND MORE EXPANSIVE IN CVRG NWD FOR TODAY THRU FRI BUT
IN LATER PRDS WHERE GFS IS NOT PREFERRED ETSS/ESTOFS
MAY BE LESS RELIABLE.


.WARNINGS...PRELIMINARY. ANY CHANGES WILL BE COORDINATED THROUGH
AWIPS 12 PLANET CHAT OR BY TELEPHONE:

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
.ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON...
     GALE POSSIBLE SUN.
.ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS...
     GALE POSSIBLE SUN INTO SUN NIGHT.
.ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR...
     GALE POSSIBLE SUN INTO SUN NIGHT.
.ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR...
     GALE POSSIBLE SUN INTO SUN NIGHT.
.ANZ835...INNER WATERS FROM CAPE FEAR TO 31N...
     GALE POSSIBLE SUN INTO SUN NIGHT.

$$

.FORECASTER KOSIER/BANCROFT. OCEAN PREDICTION CENTER.




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