Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 311335
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
935 AM EDT FRI JUL 31 2015

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

GOES VIS IMGRY INDC A CDFNT OVR NT1 AND NRN NT2...AND ALSO AN AREA
OF LOW PRES JUST S OF CAPE HTRS WITH A TROF EXTENDING TO THE S.
THE IMGRY AND THE LGTNG DENSITY PROD BITH INDC AN AREA OF SHOWERS
AND TSTMS ALNG THE TROF IN THE UNSTABLE EVRNMT OVR THE GLF
STRM...AND ALSO A FEW ALNG THE FRNTL BNDRY TO THE N. WL MAINTAIN
MENTION OF TSTMS AND SHOWERS IN THE FCST...BUT MAIN CONCERN IS
DVLPMT OF GALES IN SW FLOW OVR ZONE ANZ925. RSCAT FM 09Z INDC 25
TO 30 KT AHD OF THE TROF...AND THE EARLIER 02Z ASCAT INDC 20 KT
WITH A FEW 25 KT BARBS. CRNT SFC RPRTS INDC WND SUP TO 25 KT OVR
SRN NT2...THO NONE ARE NEAR THE AREA WHERE THE MDLS INDC THE MAX
WNDS. THE 00Z GFS WNDS INDC GALES WL DVLP AHD OF THE TROF BY 18Z
THIS AFTN...THO THE 06Z GFS BACKED OFF SLGTLY. THE 00Z ECMWF/UKMET
ARE WKR...WITH ONLY ABT 25 KT. THE 00Z GEM AND 06Z NAM AGREE...AND
ALSO INDC GALES FOR THIS AFTN. GFS MDL STABILITY INDICES INDC A
MRGNLLY UNSTABLE ENVRMT...WITH A WK H5 VORT...PROVIDING SOME FRCG.
GFS 925 MB WNDS INDC A FEW GALES...AS A THE RGT ENTRANCE RGN OF A
JET STRK SETS UP OVRHD. ATTM CONFDC IS LOW TO MDT WITH THE
GALES...AS SPRT IS MRGNL. THE PREV FCST CARRIED THE GL WRNG...SO
PLANNING ON KEEPING IT SINCE THERE IS SOME SPRT.

OTRW...THE 06Z GFS HAS NOT CHANGED MUCH FM THE 00Z RUN. THE MDLS
AGREE SOMEWHAT...THO TMG AND INTSNTY DIFFS CONT FOR THE SYS ON
MON. WITH NO CLEAR TREND APPEARING IN THE 06Z GUID...PLANNING ON
NOT MKG ANY SIG CHANGES FM PREV FCST.

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

OVER THE SHORT TERM...THE PRIMARY FOCUS REMAINS ON A SFC LOW FCST
TO TRACK NE ACRS THE NT2 WTRS. THE 00Z MDLS ARE IN RSNBLY GOOD
AGRMT IN RGRDS TO THEIR FCST TRACKS OF THIS LOW...WITH IT TRACKING
NE ACRS THE CNTRL/NE NT2 WTRS TODAY/TONITE...WITH THE 4KM 00Z
NAM/GEM/UKMET ALL CONTG TO FCST A MR IDENTIFIABLE LOW CENTER. IN
GNRL THE 00Z MDLS ALL FCST A SWLY GRADIENT INADVOF THIS LOW WITH
MAX WINDS AT LEAST UP TO 25 OR 30 KT. THE BIGGEST FCST QUESTION
THO IS WHETHER THIS GRADIENT WL OR WL NOT REACH GALE FORCE ACRS
THE OUTERMOST CNTRL NT2 WTRS. WITH THE 00Z NAM/GEM FCSTG SM GALE
FORCE ASCD BL WINDS IN THIS GRADIENT AND THE USUALLY CONSERVATIVE
00Z UKMET FCSTG SOLID 25-30 KT BL WINDS...WL GO AHEAD AND CONT
WITH THE PREVLY FCSTD LOW TO MOD CONFIDENCE MARGINAL GALES FOR
ZONE ANZ925 TODAY. THEREFORE TO BEST DEPICT THIS GRADIENT...WL
POPULATE OUR FCST WIND GRIDS WITH THE 00Z GFS 30M BL WINDS FOR
TODAY...WITH SM ADDITIONAL EDITS IN DEFERENCE TO THE 00Z
NAM/UKMET. THEN TONITE THRU SAT NITE AS THE MDLS FCST A GNRLY WEAK
WSWLY GRADIENT TO DVLP IN THE WAKE OF THE SFC LOW THRUT MUCH OF
THE CSTL/OFSHR WTRS...WL TRANSITION TO POPULATING WITH THE WEAKER
00Z GFS 10M BL WINDS. SO PER THESE FCST WINDS ANTICIPATE MAKING
ONLY GNRLY MINOR SHORT TERM CHNGS IN THE NEXT OFSHR FCST PACKAGE.

IN THE LONG RANGE...THE 00Z MDLS GNRLY AGREE THAT MOST SIG
FEATURE WL BCM A COLD FRONT FCST TO APRCH FM THE NW MON/MON
NITE...THEN DRIFT OFSHR INTO THE NT1 AND NWRN NT2 WTRS TUE/TUE
NITE. THE 00Z GEM/UKMET BOTH LOOK TO HV SM CONVECTIVE FEEDBACK
PROBLEMS WITH THE SPURIOUS SFC LOWS THEY FCST TO MOV OFSHR INADVOF
THIS FRONT. HENCE WULD FAVOR A BLENDED 00Z GFS/ECMWF SOLUTION FOR
THIS FROPA. FOR THE MOD STRONG SSWLY GRADIENT FCST BY ALL OF THE
MDLS TO DVLP INADVOF THIS FRONT...BELIEVE THE 00Z GFS IS LKLY
SLIGHTLY TOO STRONG WHL THE 00Z ECMWF IS LKLY SLIGHTLY TOO WEAK.
THEREFORE A COMPROMISE BTWN THE TWO MDLS LOOKS RSNBL. THEREFORE
PLAN ON POPULATING OUR LONG RANGE FCST WIND GRIDS WITH THE 00Z GFS
10M BL WINDS ON SUN...THEN WL TRANSITION TO A 50/50 BLEND OF THE
00Z GFS 10M AND 00Z ECMWF BL WINDS ON SUN NITE THRU TUE NITE. SO
SINCE A BLENDED GFS/ECMWF SOLUTION WAS PREVLY USED...DO NOT
ANTICIPATE MAKING ANY MAJOR LONG RANGE CHNGS TO THE PREV OFSHR
FCSTS.

SEAS...THE 00Z WAVEWATCH III AND 00Z ECMWF WAM HV BOTH
INITIALIZED THE SEAS TOO LOW OVER THE FAR SE NT2 WTRS (WHICH WL
HV TO BE EDITTED FOR OVER THE IMMED SHORT TERM)...BUT ELSWHR LOOK
RSNBL. WITH THE DIFFERENCES BTWN THE TWO MDLS BEING MINIMAL THRU
THE SHORT TERM...AND THEN SINCE A 00Z GFS/ECMWF BLEND WL BE USED
FOR THE FCST WINDS IN THE LONG RANGE...PLAN ON USING A 50/50 BLEND
OF THE 00Z WAVEWATCH III AND 00Z ECMWF WAM FOR THE FCST SEAS THRUT
THE ENTIRE FCST PERIOD THRU TUE NITE.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
.ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON...
     GALE TODAY.

$$

.FORECASTER KELLS/VUKITS. OCEAN PREDICTION CENTER.



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