Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 260047
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
847 PM EDT SAT OCT 25 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 APRCHS FM THE NW...THE WSWLY GRADIENT ACRS THE SW
MOST NT1 AND NW MOST NT2 WTRS HAS BEGUN TO STRENGTHEN WITH MAX
WINDS UP TO 20 TO 25 KT PRETTY MUCH AS PREVLY EXPECTED. ELSWHR
LITE WINDS PREVAIL.

OVER THE SHORT TERM...THE LATEST MDLS ARE IN VERY GOOD AGRMT
TIMING-WISE FOR THE COLD FRONT TO MOV OFSHR TONITE INTO NT1 AND NW
NT2 WTRS...THEN CONT SE ACRS THE RMNG OFSHR WTRS SUN INTO SUN NITE
WHILE THE ATTENDANT SFC LOW INTENSIFIES NE OF THE NT1 WTRS. THE
BIGGEST FCST CHALLENGE REMAINS HOW STRONG WL THE WNWLY GRADIENT
BCM BEHIND THE FRONT. THE PREV FCST USED THE 12Z GFS 30M BL WINDS
FOR THIS GRADIENT WHICH RESULTED IN MARGINAL GALE WRNGS ACRS THE
SRN NT1 AND NRN NT2 WTRS. WITH THE 18Z GFS RMNG CONSISTENT AND FCSTG
VERY SMLR WINDS AND THE USUALLY CONSERVATIVE 12Z UKMET/ECMWF ALSO
FCSTG SOLID 25-30 KT BL WINDS OVER THESE WTRS...DO NOT PLAN ON
REPOPULATING THESE 12Z GFS 30M WINDS AND WL JUST MAKE SM MINOR
EDITS IN DEFERENCE TO THE 12Z UKMET/ECMWF. SO DO NOT PLAN ON
MAKING ANY SIG SHORT TERM CHNGS TO THE PREV OFSHR FCSTS.

IN THE LONG RANGE...THE LATEST GLOBAL MDLS GNRLY AGREE THAT THE
ONLY SIG FEATURE WL BE A WEAKER COLD FRONT MOVG OFSHR WED INTO
THU...THEN BCMG STNRY SW-NE ACRS THE NT2 WTRS THU NITE. TO BE MR
IN LINE WITH THE LATEST WPC MEDIUM RANGE GUIDANCE PREFER THE
SLIGHTLY SLOWER 12Z ECMWF/GEM/NAVGEM FROPA VS THE FASTER 18Z
GFS/12Z UKMET. SO SINCE THE 12Z ECMWF BL WINDS WERE USED FOR THIS
FROPA ANTICIPATE MAKING ONLY MINIMAL LONG RANGE CHNGS IN THE NEXT
OFSHR FCST PACKAGE.


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

SUMMARY...A WEAK RIDGE OF HIGH PRES IS CROSSING THE OFF WTRS THIS
AFTN. THE MORNING ASCAT PASS INDICATED MAX WINDS NR 25 KT
OCCURRING OVR THE FAR NE NT2 OFF WTRS WITH WINDS GNRLY 20 KT OR
LESS ELSEWHERE. THE RIDGE WILL PASS E OF THE OFF WTRS THIS EVE AS
A COLD FRONT APPROACHES FROM THE NW. RATHER STRONG LOW PRES ASSOC
WITH THE FRONT WILL ALSO MOVE SE AND REACH MAINE EARLY SUN. THE
FRONT WILL CROSS THE WTRS TNGT INTO SUN NGT. A BRIEF PD OF GALES
IS STILL FCST BEHIND THE FRONT IN THE STRONG COLD AIR ADV OVR SRN
NT1 AND NRN NT2 WTRS BY SUN NGT. IMPROVING CONDITIONS ARE
EXPECTED TO DVLP MON AND MON NGT AS HIGH PRES SLIDES E OVR THE
WTRS. THE HIGH WILL PASS E OF THE REGION TUE AS THE NEXT COLD
FRONT APPROACHES FROM THE NW. THIS FRONT WILL NEAR THE COAST TUE
NGT...AND THEN MOVE RATHER SLOWLY SE OVR THE WTRS WED INTO WED
NGT...LKLY STALLING OVR THE SE NT2 WTRS THU INTO THU NGT AS WK
HIGH PRES MOVES E OFF THE NEW ENGLAND AND MID ATLC COASTS.

MODELS...THE 12Z MODELS ARE IN VRY GOOD AGREEMENT OVR THE OFF WTRS
THRU TUE NGT. WE WILL THEREFORE RELY ON THE 12Z GFS FOR THE AFTN
PACKAGE THRU EARLY WED MORNING. WE WILL USE A BLEND OF THE 30M
AND 10M BL WINDS FOR THE FCST N OF THE GULF STREAM...OR ROUGHTLY
N OF 38N...FOR THE PERIOD BEGINNING TNGT...AND CONTG THRU MON
NGT. THIS WILL PRODUCE A BRIEF PERIOD OF GALES BY SUN NGT FOR
ZONES 805... 810...915...AND 905. THESE ZONES APPEAR TO HAVE THE
BEST CHANCE FOR MORE SUSTAINED GALES PER THE LATEST NSHARP GFS
MDL SOUNDINGS FROM THAT REGION. MORE WIDESPREAD GALE FORCE GUSTS
ARE LKLY BEYOND THIS AREA FROM THE NEW ENGL WTRS S TO OFF THE MID
ATLC COAST LTR TNGT INTO MON. FOR THE AFTN PACKAGE WE HAVE
DECIDED TO TONE DOWN THE WINDS SLIGHTLY FROM THE 30M WINDS USED
PRVSLY AS THE REMAINING NON-GFS BL WINDS ARE ALL SUB-GALE FOR LTR
SUN AND SUN NGT. CONFDC LVLS IN THESE GALES OCCURRING IS STILL
MODERATE FOR THE AFTN PACKAGE. ELSEWHERE THE 10M BL WINDS FROM
THE GFS APPEAR REASONABLE...AND WILL BE USED FOR THE FCST THRU
12Z WED OR 12Z/29 OCT. BEYOND THAT TIME MDL DIFFERENCES BEGIN TO
INCREASE. THE 12Z GFS BECOMES A SLIGHT OUTLIER IN MOVG THE FRONT
FASTER THAN THE REMAINING 12Z GLBL MDLS FOR WED INTO THU. THE 12Z
ECMWF APPEARS TO BE A SOMEWHAT BETTER FIT WITH THE MAJORITY OF
THE GUID WHICH WILL KEEP THE FRONT MOVG SLIGHTLY SLOWER THAN THE
12Z GFS FOR LTR WED INTO THU NGT. AS A RESULT...FROM 15Z WED THRU
THU NGT WE WILL TREND THE NEXT OFF FCST PACKAGE TOWARD THE 12Z
ECMWF MDL GUID.

.SEAS...SEA HTS RANGE FROM NR 8 FT OVR WTRS WELL OFF THE MID ATLC
AND NE COASTS TO 2 FT CLOSER TO THE COASTAL WTRS FROM NEW ENGLAND
S TO THE CAROLINAS. FOR THE MOST PART THE 12Z WNA WV WATCH III
MDL GUID APPEARS TO HAVE INITIALIZED WELL OVR THE OFF WTRS PER
THE LATEST OBS. WE WILL ACCEPT THE WNA WW3 MDL OUTPUT FOR THE
NEXT FCST PACKAGE INTO EARLY WED...AND THEN TREND THE FCST TOWARD
THE ECMWF WAM WV GUID AS WE TREND THE WIND FCST AWAY FROM THE GFS
TOWARD THE 12Z ECMWF AT THAT TIME AS WELL.

.EXTRATROPICAL STORM SURGE GUIDANCE...THE LATEST ESSG APPEARS
REASONABLE OVR THE REGION INTO NEXT WK WITH NO MAJOR SURGE EVENTS
EXPECTED. THE ESTOFS GUID AND ETSS GUID ARE FAIRLY CONSISTENT
THRU EARLY AND MIDDLE PARTS OF NEXT WK. A MODEST NEG SURGE WILL
DVLP FROM THE MID ATLC COAST NORTHWARD SUN...AND PERSIST INTO TUE
AS A STRONG OFFSHORE WIND FIELD DVLPS OVR THE NT1 AND NRN NT2
WTRS LTR TNGT INTO MON NGT.

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
.ANZ805...GEORGES BANK WEST OF 68W...
     GALE SUN NIGHT.
.ANZ810...SOUTH OF NEW ENGLAND...
     GALE SUN NIGHT.

.NT2 MID ATLC WATERS...
.ANZ915...HUDSON CANYON TO THE GREAT SOUTH CHANNEL...
     GALE SUN NIGHT.
.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...
     GALE SUN NIGHT.

$$

.FORECASTER VUKITS/MILLS. OCEAN PREDICTION CENTER.



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