Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 191255
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
855 AM EDT SUN APR 19 2015

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

AS DVLPG LOW PRES SE OF NOVA SCOTIA CONTS TO MOVE OFF TO THE E MAX
ASCD WINDS IN ITS NLY GRADIENT IN ITS WAKE ACRS THE OFSHR WTRS ARE
IN THE 20-30 KT RANGE...HIGHEST ACRS THE NE NT2 WTRS. MAX ASCD
SEAS OVER THESE WTRS ARE LKLY IN THE 6-9 FT RANGE WHICH ARE IN
LINE WITH THE 06Z WAVEWATCH III AND 00Z ECMWF WAM MDLS.

OVER THE SHORT TERM...THE LATEST MDLS REMAIN CONSISTENT IN FCSTG
THE SFC LOW TO CONT OFF TO THE E TODAY WHILE A HIGH PRES RIDGE
BLDS OFSHR. THEN AS A THE RIDGE PASSES E OF THE OFSHR WTRS THE
MDLS ARE IN RSNBLY GOOD AGRMT THAT A WARM FRONT WL MOVE NE OFF THE
MID ATLC COAST TONITE...THEN CONT NE UP THE COAST THRU TUE WITH A
STRONG ESELY GRADIENT DVLPG TO ITS N AND NE. THE PREV OFSHR FCST
PACKAGE USED THE 00Z GFS 10M BL WINDS FOR THIS GRADIENT AND WITH THE
06Z NAM/GFS FCSTG SMLR WINDS DO NOT PLAN ON REPOPULATING. SO PLAN
ON MAKING ONLY VERY MINOR CHNGS TO THE PREVLY FCSTD GALE WRNGS AND
ASCD FCST CONDS.

IN THE LONG RANGE...THE LATEST GLOBAL MDLS HV COME INTO SMWHT
BETTER AGRMT THAT THE MOST SIG WX FEATURE WL COLD FRONT MOVG
SLOWLY OFSHR WED NITE THRU THU NITE. OVERALL THE 06Z GFS REMAINS
CONSISTENT VS ITS PREV 00Z RUN WITH THIS FROPA AND HINTS AT PSBL
SWLY PREFRONTAL GALES DVLPG ACRS THE OUTERMOST NRN NT2 WTRS
THU/THU NITE. FOR NOW THO DUE TO THE CURRENT MDL DISPARITY...BLV
THE PREVLY USED 00Z GFS/ECMWF COMPROMISE STIL LOOKS RSNBL FOR THIS
FROPA. SO AS A RESULT WL CONT TO HOLD OFF ON FCSTG ANY PSBL ASCD
GALES WITH FROPA IN THE NEXT OFSHR FCST PACKAGE.

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


THE MODELS HAVE COME INTO BETTER AGREEMENT THROUGH MOST OF THE
FORECAST...WITH SOME MODEL DFFRCS TWDS THE END OF THE FCST PERIOD.
IN THE IMMED FCST...COLD FRONT ON SCD TO QUICKLY MOVE S OF HTTRS
CNYON TDY....WITH N TO NE SURGE IMMED FLLWG FRONT TO DMNSH AS
WINDS VEER TO THE S TO SE. THE FRONT WILL BEGIN TO RETURN BACK TO
THE N TNGT...WITH SE GALES DVLPNG JUST BEFORE 12Z N OF HATTERAS
CANYON. MAIN CONCERN IS EXTEND OF SRLY GALES TNGT THRU EARLY TUE
AHD OF THE STRNGTHNG WARM FRONT. SE FLOW WL INIT BE UNSTABLE... UT
EXPECT INCRSNG LL STABILITY AHD OF THE FRONT... KEEPING WINDS
LOWER...TWDS THE GFS 10M FCST LVL. HOWEVER...LL 925 MB INFLOW
ALREADY FCST TO BE AT WELL ESTBLSHD AT 65 KT BY 12Z MON AND GRADU
INCRCSNG THRU MON NGT. NEW GFS 10M WINDS FCST NR 35 KT THRU THIS
TIME. THE UKMET AND ECMWF 10M WINDS ARE SMLR...SO CNFDC IS VRY GD
FOR GALES CONTG AHD OF THIS FRONT. MODELS ARE IN VRY GD AGRMNT ON
TIMING OF THE WARM FRONT.

AS THE AS ASSD TRAILING COLD FRONT SWEEPS E TUE...MODELS BGNG TO
AGREE MORE ON HIGH PRES RDG FILLING IN BEHIND THE FRONT. NEW
GFS/UKMET/GEM/ECMWF BRINGS HIGH OFFSHR TUE NGT/EARLY WED WITH THE
GFS/GEM MAINTAINING A MOD SW TO NE RDG...WHICH SETS UP AN INCRSNG
SRLY FLOW LATE WED AHD OF ADVNCG COLD FRONT. THE GFS WINDS LK A
BIT OVRDN IN THE SRLY FLOW LATE WED...AND WL LIMIT TO 30 KT PER
UKMET/ECMWF. THE GFS/ECMWF/GEM IN FAIRLY DECENT AGREEMENT ON SPEED
OF FRNOT FCST TO SLIDE E OVER THE WATERS THU. BY 12Z FRI... THE
GEM AND UKMET FAVOR THE LOC OF THE MAIN SFC LOW ABT 200 NM SE OF
NOVA SCOTIA...WHILE THE GFS/ECMWF FAVORS A LOC 400 NM SW OF HERE.
THE GFS ENSMBL MEMBERS ONLY PROVIDE SOME SUPPORT FOR THE OPRNL
RUN. WL USE A GFS/ECMWF BLEND FOR THU AND THU NGT. THIS LATEST
GFS/ECMWF FCST OF LOW DVLPNG THU NGT JUST NE OF BALT CANYON MAY
REQUIRE GALES IS THE MODELS STAY CONSISTENT WITH THIS SYNOP
FEATURE.


.SEAS...THE MULTIGRID WAVEWATCH III INITLD WELL TNGT...AND FCST
GDNC LKS GOOD. THE WW AND ECMWF WAM COMPARE WELL WITH MANLY JUST
MINOR DFFRNCS. WL STICK WITH PRVS IDEA OF BLENDING THE TWO MODELS.
HOWEVER...THE WAM LOOKS TOO HIGH WITH THE SEAS IN THE SRLY
FLOW...ESP MON AND MON NGT. WL USE A 2/1 WW/WAM BLEND THRUOGH THE
FCST.


.EXTRATROPICAL STORM SURGE GUIDANCE...AS THE SELY GRADIENT IS FCST
TO STRENGTHEN LATE SUN AND THEN SPREAD NWD UP THE COAST INTO TUE
NITE...SMLR TO THEIR PREV RESPECTIVE RUNS THE 00Z ESTOFS CONTS TO
FCST A SLIGHTLY MR SIG POSITIVE TO SPREAD NWD UP THE COAST THAN
FCST BY THE 12Z ETSS. AGREE WITH PRVS FCST AND STILL BLV A
COMPROMISE BTWN THE TWO MDLS IS BEST.



.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
.ANZ800...GULF OF MAINE...
     GALE MON NIGHT.
     GALE POSSIBLE TUE.
.ANZ805...GEORGES BANK WEST OF 68W...
     GALE MON NIGHT.
.ANZ900...GEORGES BANK EAST OF 68W...
     GALE MON NIGHT.
     GALE POSSIBLE TUE.
.ANZ810...SOUTH OF NEW ENGLAND...
     GALE MON INTO MON NIGHT.
.ANZ815...SOUTH OF LONG ISLAND...
     GALE MON.

.NT2 MID ATLC WATERS...
.ANZ820...HUDSON CANYON TO BALTIMORE CANYON...
     GALE TONIGHT INTO MON.
.ANZ915...HUDSON CANYON TO THE GREAT SOUTH CHANNEL...
     GALE MON INTO MON NIGHT.
.ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL...
     GALE TONIGHT INTO MON NIGHT.
.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...
     GALE TODAY.
     GALE MON INTO MON NIGHT.
     GALE POSSIBLE TUE.
.ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N...
     GALE MON INTO MON NIGHT.
.ANZ825...INNER WATERS FROM BALTIMORE CANYON TO CAPE CHARLES LIGHT...
     GALE TONIGHT INTO MON.
.ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON...
     GALE TONIGHT INTO MON.

$$

.FORECASTER VUKITS/PROSISE. OCEAN PREDICTION CENTER.



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