Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 291217
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
817 AM EDT WED JUL 29 2015

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

UPDATE...06Z NCEP SFC ANALYSIS SHOWS A STNRY FNT EXTNDG OVER THE
SRN NT2 WTRS AND A WEAK COLD FNT JUST N OF THE GULF OF MAINE...BUT
OTHERWISE WEAK HI PRES RDG PREVAILS ACROSS THE OFSHR WTRS. LATEST
AVAIL ASCAT PASSES FROM LAST NITE SHOW LIGHT WINDS OF 15 KT OR
LESS ACROSS THE OFSHR ZONES. LIGHTNING DENSITY DATA AT 1110Z THIS
MRNG SHOWS SCT SHOWERS/TSTMS IN THE OUTER OFSHR ZONES IN THE SRN
NT2 WTRS. WEAK COLD FNTS WILL MOVE ACROSS THE NT1 AND NRN NT2
WTRS TODAY INTO TONITE...FRI INTO EARLY SAT...THEN AGAIN SUN INTO
SUN NITE.

MODELS...THE MED RNG MDLS ARE IN GUD OVERALL AGREEMNT ACROSS THE
OFSHR WTRS THRU THE FCST PRD. THE UKMET WHICH HAD BEEN AN OUTLYER
SOLN YDAY...HAS NOW CONVERGED INTO CLOSE AGREEMNT WITH THE GFS. THE
GFS CONTS TO LOOK VRY REPRESENTATIVE AND HAS HAD GUD RUN TO RUN
CONSISTENCY...AND ALSO IT HAS GUD SUPPORT FROM THE LATEST WPC MED
RNG FCSTR GUIDANCE. THE GFS 10M SOLN LOOKS LIKE A GUD MEDIAN SOLN
BTWN THE GFS 30M AND ECWMF...SO IT WILL BE USED FOR THE WIND GRIDS
THRU THE ENTIRE FCST PRD. AM NOT PLANNING TO MAKE ANY SIGNIF
CHANGES TO THE CURRENT FCST TREND.

SEAS...WNA VERSION OF THE WAVEWATCH III MDL AND ECMWF WAM BOTH
INITIALIZED WELL OVER THE OFSHR WTRS VERSUS LATEST BUOY OBS AND
JASON PASSES. THE MDLS ARE IN DECENT OVERALL AGREEMNT FOR MOST OF
THE FCST PRD...AND THE WNA WAVEWATCH III MDL WILL BE USED FOR THE
SEA HT GRIDS THRU THE FCST PRD IN ORDER TO MATCH UP WITH THE
PREFERRED GFS ATMOS MDL.

EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

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

OVER THE SHORT TERM...THE NEW 00Z MDLS REMAIN CONSISTENT OVER THE
NRN WTRS WITH THE MOST SIG FEATURE EXPECTED TO BE A WEAK COLD
FRONT APRCHG FM THE NW THU...THEN MOVG OFSHR THU NITE WITH A MOD
STRONG (PRIMARILY 15 TO 20 KT) SWLY PREFRONTAL GRADIENT. OVERALL
BELIEVE THE 00Z GFS SOLUTION FOR THIS FROPA LOOKS REPRESENTATIVE
AND AS A RESULT WL POPULATE OUR SHORT TERM FCST WIND GRIDS WITH
ITS 10M BL WINDS WHICH ARE IN LINE WITH THE 00Z UKMET/ECMWF BL
WINDS. FURTHER S THE 00Z MDLS HV COME INTO BETTER AGRMT IN RGRDS
TO A SFC LOW FCST TO DRIFT N ALONG THE STNRY FRONT INTO THE SRN
NT2 WTRS THU/THU NITE. IN RGRDS TO THE FCST TRACK OF THIS
LOW...OTHER THAN THE 00Z GEM/ECMWF BOTH LOOKING A LTL TOO
FAST...THE 00Z NAM/GFS/UKMET/GEFS MEAN NOW ALL SHARE SMLR TRACKS.
IN RGRDS TO THE ASCD FCST GRADIENTS...THE 00Z MDLS ALL FCST THE
STRONGEST WINDS TO REMAIN OVER THE E SEMICIRCLE OF THE LOW. FOR
NOW PLAN ON ALSO USING THE 00Z GFS 10M BL WINDS FOR THIS SYSTEM
WITH SM ADDITIONAL MINOR EDITS IN DEFERENCE TO THE SMWHT WEAKER
00Z UKMET/ECMWF BL WINDS. SO SINCE THE PREV 12Z GFS 10M BL WINDS
WERE USED...DO NOT ANTICIPATE MAKING ANY MAJOR SHORT TERM CHNGS TO
THE PREV OFSHR FCSTS.

IN THE LONG RANGE...THE 00Z MDLS CONT TO DIFFER IN HOW THE SFC
LOW OVER THE SRN NT2 WTRS WL PROGRESS. THE 00Z GEM CONTS TO LOOK
TOO PROGRESSIVE. THE 00Z ECMWF NOW LOOKS TOO WEAK AS IT FCSTS THE
LOW TO WEAKEN INTO AN OPEN WAVE OR SFC TROF. THE 00Z UKMET...WHOSE
PREV 12Z RUN WAS THE LEAST PROGRESSIVE AND STRONGEST
SOLUTION...HAS NOW COME INTO MUCH BETTER AGRMT WITH THE 00Z GFS.
THE 00Z GFS ALSO REMAINS CONSISTENT VS ITS PREV 18Z RUN IN FCSTG
THE SFC LOW TO TRACK NE ACRS THE CNTRL NT2 WTRS LATE FRI/FRI
NITE...THEN CONT NE ACRS THE NE NT2 WTRS SAT...WHICH IS SPRTD BY
THE 00Z GEFS MEAN. THEREFORE WULD FAVOR A 00Z GFS/UKMET SOLUTION
FOR THIS LOW. IN RGRDS TO THE ASCD FCST GRADIENTS...PER THE 00Z
GFS/UKMET IT LOOKS CLOSE AS TO WHETHER THE SSWLY GRADIENT INADVOF
THIS LOW WL REACH GALE FORCE ACRS THE OUTERMOST CNTRL/NERN NT2
WTRS FRI NITE/EARLY SAT. BUT FOR NOW GIVING SM CREDENCE TO THE
WEAKER 00Z ECMWF...WL HOLD OFF ON FCSTG ANY PSBL GALES. THEREFORE
PLAN ON CONTG TO POPULATE WITH THE REPRESENTATIVE 00Z GFS 10M BL
WINDS ON FRI THRU SAT NITE. THEN WL CONT TO POPULATE WITH THE 00Z
GFS 10M BL WINDS FOR SUN/SUN NITE FOR A MOD SLY GRADIENT
PERSISTING THRUT MUCH OF THE WTRS. SO NO MAJOR LONG RANGE CHNGS
ARE PLANNED FOR THE NEXT OFSHR FCST PACKAGE.

SEAS...THE 00Z WAVEWATCH III HAS INITIALIZED WELL. SINCE THE 00Z
GFS OVERALL WL BE FAVORED...WL POPULATE OUR FCST WAVE GRIDS WITH
ITS ASCD 00Z WAVEWATCH III THRU SUN NITE.

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

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER SCOVIL/VUKITS. OCEAN PREDICTION CENTER.



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