Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 210155
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
955 PM EDT MON APR 20 2015

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

00Z OPC PRELIM ANAL AND GOES IR IMAGERY SHOW A WRM FNT ENTERING S
OF NEW ENGLAND ZONES AND NE NT2 WTRS AND IS THE FOCUS OF STRONGEST
WNDS TO ITS NE. BUOY 44020 RPT SUGGESTS THERE ARE MRGL GALES AHD
OF FNT AND TO SE BUOY 44008 HAS WNDS APCHG GALE FORCE. EARLIER
ASCAT IMAGE ALONG WITH MORE RECENT SHIP AND BUOY OBS INDICATE GFS
10M WNDS APPR REPRESENTATIVE.

THE 18Z GFS DID LTL TO CHANGE OVRALL THINKING FOR NEXT 5 DAYS. 18Z
GFS IS SIMILAR TO ITS PREVIOUS RUN BUT ON WED DOES SHOW A SHARPER
FNTL TROF ENTERING NRN NT2 WTRS LATER WED AND FCSTS A DEEPER AND
MORE AMPLIFIED SOLN OF LOW FORMING ON FNT BY EARLY THU...SOMEWHAT
DIFFERENT FM 06Z/12Z RUNS. FOR NOW WILL DISCOUNT THE 18Z GFS WHICH
DVLPS 10M WNDS OF 35 KT OFF NRN MID ATLC CST LATER WED. 18Z GEFS
ENSEMBLE MEMBERS SPRT THE LESS AMPLIFIED 12Z GFS ON WHICH PRESENT
GRIDS ARE BASED THRU 09Z THU. 12Z ECMWF/UKMET SPRT 12Z GFS IN THIS
TIMEFRAME. ONCE AGAIN THERE IS INCRG DISPARITY AND SPREAD OF SOLNS
THU AND BYND...ESPCLY LATER FRI AND SAT. WITH 18Z GFS RELATIVELY
CONSISTENT WITH ITS PREVIOUS RUN THE PREVIOUSLY USED MDL BLEND
BTWN GFS AND UKMET APPRS RSNBL. PLAN TO MAKE MINOR ADJ IN INITL
PRD BUT OTRW KEEP GRIDS.

12Z ECMWF WAVE MDL APPPRS CLOSER TO 00Z SEA STATE ANAL THAN 18Z
WNA WAVEWATCH III AND PRESENT GRIDS BASED ON 12Z WNA WW3 ARE
ALREADY BOOSTED A COUPLE OF FT ACCORDINGLY DURING PERIOD OF
STRONGER WINDS IN FIRST PRD. AT LEAST THRU WED NIGHT 12Z WNA WW3
OTRW APPRS THE WAY TO GO.
-----------------------------------------------------------------
PREVIOUS DISCUSSION...

THE OVERALL PATTERN ACROSS THE WRN ATL WILL REMAIN VERY
PROGRESSIVE DURING THE UPCOMING WEEK AND THIS WILL PRESENT A
SERIES OF CHALLENGES. SAT PIX SHOW A COLD FRONT APPROACHING THE
ERN SEABOARD WHILE A WARM FRONT EXTENDS E/W OVR THE NRN NT2
WATERS. ASCAT PASS FROM LATE THIS MORNING INDICATES WINDS TO 40 KT
OVR PTNS OF THE BALT AND HUDSON CANYON WATERS. THERE ARE NO OBS IN
VCNTY OF MAX WINDS ALTHOUGH I AM EST WAVE HGTS NR 16 FT AND
RISING. THE GLOBAL MODELS ARE ALL IN GENERAL AGREEMENT THROUGH 72
HRS...THEN BEGIN TO DIVERGE...AND BY DAY 5 THEY ARE WIDELY
DIFFERENT. AT 06Z 04/25 THE ECMWF DEVELOPS A VERY DEEP LOW NEAR
40N/60W...THE OTHER MODELS ARE MUCH WEAKER WITH THAT DEVELOPMENT.
FOR THAT REASON IM GOING TO HAVE TO TOSS OUT THE ECMWF DURING THIS
TIME PERIOD. DURING THE FIRST 3 DAYS I WILL POP THE GRIDS USING
EITHER THE 10M OR 30M GFS...DEPENDING ON THE STABILITY. FOR 12Z
THU THROUGH 12Z SAT I WILL USE A 50/50 BLEND OF THE GFS AND
UKMET. AFTER 12Z SAT THE MODELS ARE SIG DIFFEERENT WITH A LOW
SYSTEM FCST TO MOVE OFF THE SE CST. THE UKMET IS VERY FAST AND
DEEP WHILE THE ECMWF IS MUCH SLOWER. THE GFS SOLN IS THE FURTHEST
S OF THE MODELS AND NOT AS STRONG. DURING THIS TIME FRAME GIVEN
THE WIDE DESCREPENCY IT IS IMPOSSIBLE TO BLEND THE
MODELS...THEREFOR I NEEDED TO PICK ONE AND IT IS THE GFS.

SEAS...WILL USE THE WW3 THROUGHOUT THE FCST PERIOD WITH SOME MINOR
ADJUSTMENTS...NEEDING TO INCREASE BY 1 FT OR TWO IN CERTAIN HIGH
WIND AREAS.

.EXTRATROPICAL STORM SURGE GUIDANCE...AS THE SELY GRADIENT CONTS
TO STRENGTHEN TODAY AND SHIFT NEWD UP THE COAST INTO TUE NITE...
THE 12Z ESTOFS CONTS ITS PREV TRENDS OF FCSTG A SLIGHTLY A
POSITIVE SURGE OF 1 TO 2 FT FM THE NRN NC COAST THRU SRN NEW
ENGLAND AND INTO THE GF OF MAINE TDY..THEN GRADU EASING FM S TO N
LATE TNGT INTO TUE NGT. THE ETSS FCST VALUES ARE 1 FT OR LESS.

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
.ANZ800...GULF OF MAINE...
     GALE TONIGHT INTO TUE.
.ANZ805...GEORGES BANK WEST OF 68W...
     GALE TONIGHT.
.ANZ900...GEORGES BANK EAST OF 68W...
     GALE TONIGHT.

.NT2 MID ATLC WATERS...
.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...
     GALE TONIGHT INTO TUE.
.ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N...
     GALE TONIGHT.

$$

.FORECASTER BANCROFT/SHAW. OCEAN PREDICTION CENTER.


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