Marine Interpretation Message
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AGNT40 KWNM 230046
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
846 PM EDT MON SEP 22 2014

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

AS A COLD FRONT CONTS TO PUSH SE ACRS THE CNTRL/SRN NT2 WTRS MAX
ASCD WINDS IN ITS WAKE ARE GNRLY IN THE 15-25 KT RANGE...HIGHEST
ACRS THE NT1 AND NRN NT2 WTRS. MAX ASCD SEAS ARE IN THE 8-12 FT
RANGE...HIGHEST ACRS THE ERN NT1 AND NE MOST NT2 WTRS...WHICH ARE
BEING HANDLED SLIGHTLY BETTER BY THE 18Z WAVEWATCH III VS THE 12Z
ECMWF MDL.

OVER THE SHORT TERM...THE LATEST MDLS PRESENT NO MAJOR FCST
PROBLEMS. THE MDLS AGREE THAT THE NT1 WTRS WL BE DOMINATED BY
STRONG HIGH PRES BLDG IN FM THE W AND NW TONITE THRU TUE
NITE...THEN MOVG OFSHR WED/WED NITE. FURTHER S ACRS THE NT2 WTRS THE
MDLS TO A LESSER DEGREE GNRLY AGREE THAT AS THE HIGH PRES BLDS IN
FM THE N AND A LOW PRES TROF DVLPS OFF THE SE COAST TUE/TUE NITE THAT
A STRENGTHENING ENELY GRADIENT WL DVLP. AS A COMPROMISE WL CONT TO
FAVOR A BLENDED 12Z GFS/UKMET (THE 12Z ECMWF LOOKS TOO WEAK) SOLUTION
FOR OUR FCST WIND GRIDS FOR THIS GRADIENT. SO PLAN ON MAKING
MINIMAL SHORT TERM CHNGS TO THE PREV OFSHR FCSTS.

IN THE LONG RANGE...THE 18Z NAM/GFS PROVIDE NO SIG CLARIFICATION
TO WHAT IS LKLY GOING TO BCM A COMPLEX PATTERN ACRS THE NT2 WTRS.
THE LATEST MDLS GNRLY AGREE THAT THE NT1 WTRS WL CONT TO BE
DOMINATED BY THE HIGH PRES RIDGE WITH GNRLY LITE WINDS CONTG THRU
SAT NITE. BUT FOR THE NT2 WTRS AS NOTED BELOW PREVLY...THE MDLS
CONT TO FCST SIGLY DIFFERENT SOLUTIONS FOR THE CSTL TROF AND
WHETHER ANY ASCD SIG SFC LOWS WL DVLP ON THE TROF. THE 18Z GFS
REMAINS CONSISTENT WITH ITS PREV 12Z RUN IN FCSTG AN ASCD SFC LOW
TO DVLP OFF THE MID ATLC COAST LATE WED/WED NITE...THEN TRACK ENE
ACRS THE NRN NT2 WTRS THU INTO LATE FRI WITH SM GALE FORCE ASCD BL
WINDS. THE 12Z GEM IS SMLR TO THE 18Z GFS BUT FCSTS AN EVEN
STRONGER SFC LOW. THE 12Z/18Z NAM IS SMLR TO THE 18Z GFS BUT FCSTS
A WEAKER SFC LOW. WITH THE 18Z GEFS MEAN SPRTG A MR SUPPRESSED AND
WEAKER SOLUTION THAN THE 18Z GFS...FOR NOW WITH LOW FCST
CONFIDENCE...WL CONT TO FAVOR THE WEAKER AND MR SUPPRESSED 12Z
UKMET/ECMWF SOLUTIONS FOR THE LONG RANGE WHICH ARE MR IN LINE WITH
THE LATEST WPC MEDIUM RANGE GUIDANCE. THEREFORE PLAN ON MAKING
SOME GNRLY MINOR CHNGS TO THE PREVLY POPULATED 12Z UKMET BL
WINDS...MAINLY IN DEFERENCE TO THE 12Z ECMWF...FOR THE LONG RANGE
INTO SAT NITE.



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

COLD FRONT MOVING E ACROSS THE OFFSHORE WATERS THIS AFTERNOON
WILL MOVE E OF THE WATERS BY TUE MRNG...SHOOVED SE BY STRNG HIGH
PRES BUILDING IN FM THE NW. SCATTEROMETER PASS FM 15Z TODAY
SHOWED MOD WINDS N OF BALT CNYN...WHICH WERE CLOSER TO THE GFS 30M
WINDS.

FCST CONDIFEDENCE SOON TAKES LOWERS SIGNIFICANLY AS THE MODELS
DIFFER WITH THE FCST OF THE AN INVERTED TROUGH AND/OR SFC LOW TO
DVLP OFF THE SE COAST TUE/TUE NGT AND PSBLY OFF THE MID ATLC COAST
WED. ALOFT...THE MODELS ARE IN FAIRLY DECENT GENERAL AGREEMENT
OVERALL BUT THE DFFRNCS IN THE DETAILS IS MAKING FOR THE SIG
DFFRNC ON THE PLACEMENT AND DVLMNT OF SFC TROF/LOW SCENARIO. ALL
MODELS AGREE ON UPR LOW CLOSING OFF OVR THE SE STATES BY TNGT...
MVG E...THEN TURN NE TUE AND OPENING UP. EACH MODELS DIFERS ON
THE PLACEMENT OF S/W ENERGY SHEARING AND/OR MVG OUT TO THE NE AS
THE MAIN TROF RETROGRATES WWRD.

ON THE SFC...THE ON AND OFF SFC LOW DEPENDS ON THE MODEL AND THE MODEL
RUN. THE MODELS AGREE ON BROAD SFC TROF DVLPNG OFF THE COAST
TUE...AND XTNDNG NE TO HTTRS CNYN BY 12Z WED. THE GFS/NAM FAVOR A
TROF CLOSER TO THE COAST WHILE THE UKMET EXTENDS THE TROF FTHR
EASTWARD AND THE ECMWF HAS THE A WEAKER TROF SLGTLY INLAND.
MODELS...GFS/UKMET/GEM IN GENERAL AGREEMENT IN A 20 TO 30 KT NE
GRADIENT JUST W OF THE FRONT. THE FCST DFFRNCS INCRS IN TIME AS
THE GFS/GEM DVLPS A GALE JUST E OF THE MID ATLC COAST WHILE THE
UKMET AND NAM FAVOR A WEAKER LOW. THE ECMWF REMAINS THE FLATTEST...
DVLPNG A WEAK LOW E OF THE MID ATLC COAST FRI. THE GFS LL VORT
HINT THAT IT MAY HV SOME GRIDSCALE FEEDBACK HERE. CONSIDERING THE
GEFS ONLY GIVES WK SUPPORT TO THE OPRNL GFS...THE GFS AND GEM
SOLUTION ARE CNSDRD A STRONG OUTLIER. SINCE THE UKMET TAKES THE
MIDDLE GROUND INBETEEEN THE STRNGR GFS/GEM AND THE MUCH WEAKER
ECMWF...WILL USE BLEND IT AND BLEND IN THE UKMET TUE...THEN USE
IT 100 PCT FOR WED THROUGH SAT NGT...WITH CONDIFENCE STARTING OUT
LOW TO MOD AND DECREASING IN TIME. THIS WILL KP AN AREA OF MOD E
TO NE WINDS OFF THE MID ATLC AND JUST OFF THE SE COAST FOR WED
INTO FRI...WITH LGT WINDS OVR THE NRN WATERS.

.SEAS...IS MAJOR FORECAST PRBLM NBR TWO. TODAY...THE 12Z MULTIGRID
WAVEWATCH INITLZD WELL WITH THE SUBSIDING SEAS IN THE WAKE OF
GALE CNTR AND COLD FRONT. GUIDANCE LOOKS GOOD TNGT AND TUE...THEN
GOES DOWNHILL AS THERE IS NOT A UKMET WAV MODEL TO FLLW. WILL
INCRS SEAS 25 TO 45 PCT IN THE NE FLOW OFF THE SE COAST TUE NGT
AND WED AS THE MODELS USAUALLY UNDERDOES SEAS IN MOD NE FLOW...
AGAINST THE GULF STREAM. SINCE A UKMET WAVE MODEL IS NOT AVBL...WILL
BLEND THE WAVE WATCH AND ECMWF WAM...PLACING MORE WEIGHT...LIKELY
60 TO 80 PCT ON THE WAM. WILL MANUALLY ADJUST SEAS ACCRNDG TO THE
WINDS WHEN AND WHERE PSBL.

.EXTRATROPICAL STORM SURGE GUIDANCE...ON WED...THE 12Z ESTOFS
FCSTS A POSITIVE SURGE OF 1 TO 2 FT FM LONG ISLAND S...AND 2 TO 3
FT ALONG THE MID ATLC COAST WED NGT INTO THU...BEFORE SLOWLY
DMNSHG LATER THU INTO SAT. THE ETSS MODELS HAS VALUES TO 1 FT.
SINCE THE GFS IS NOT THE PREFERRED MODLE AFT TUE NGT...NEITHER
GDNC LOOKS REASONABLE.

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER VUKITS/PROSISE. OCEAN PREDICTION CENTER.



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