Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 250027
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
827 PM EDT WED AUG 24 2016

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

UPDATE...18Z NCEP SFC ANALYSIS SHOWS A LARGE HIGH PRES RIDGE OVER
THE OFSHR WTRS...WITH A STATIONARY FRONT EXTNDG NE TO SW ACROSS
THE WTRS BETWEEN THE SRN NT2 ZONES AND BERMUDA. LATEST AVAILABLE
ASCAT AND ASCAT HI-RES PASSES FROM THIS MORNING SHOW AREAS OF
WINDS TO 20 KT IN NE FLOW OVER THE SRN NT2 ZONES...BUT OTHERWISE
INDICATE LIGHT WINDS OF 15 KT OR LESS IN THE REMAINING OFSHR WTRS.
LIGHTNING DENSITY PRODUCT DATA AT 2310Z DID NOT SHOW ANY SHOWER OR
TSTM ACTIVITY IN THE COASTAL/OFSHR WTRS.

MAIN WEATHER FEATURES...THE WEAK SUMMERTIME PATTERN IS EXPECTED TO
CONTINUE THRU THE FCST PERIOD...WITH WINDS NOT EXPECTED TO EXCEED
20 KT IN THE OFSHR WTRS. A HI PRES RIDGE WILL PASS E OVER THE
OFSHR WTRS TONITE INTO FRI. A COLD FRONT WILL APPROACH THE COAST
FROM THE NW FRI...THEN MOVE SE OVER THE OFSHR AREA FRI NITE INTO
SAT NITE WHILE WEAKENING. ANOTHER RIDGE WILL BUILD SE OVER THE
OFSHR WTRS LATE SAT AND SAT NITE...THEN E ACROSS THE NT1 WTRS SUN
AND SUN NITE. A WEAKENING COLD FRONT WILL PASS SE OVER THE NT1
AREA MON AND MON NITE. T.S. GASTON IS FORECAST TO TRACK NW
TOWARDS THE BERMUDA AREA THRU MON NITE WHILE STRENGTHENING. GASTON
IS EXPECTD TO PUSH LONG PERIOD SW SWELL INTO THE OFSHR WTRS DURING
THE SAT THRU MON NITE TIMEFRAME. REFER TO LATEST NATIONAL
HURRICANE CENTER ADVISORY FOR ADDITIONAL INFORMATION.

MODELS...THE MED RNG MDLS ARE IN VERY GUD OVERALL AGREEMNT ACROSS
THE OFSHR WTRS THRU THE FCST PERIOD...EXCEPT THE GEM DOES NOT HAVE
A COLD FRONT CROSSING THE NT1 WTRS ON MON AND MON NITE. THE GFS
10M SOLN LOOKS REPRESENTATIVE ENUF TO BE USED FOR THE WIND GRIDS
THRU AT LEAST MON NITE. AM NOT PLANNING TO MAKE ANY SIGNIF CHANGES
TO THE CURRENT FCST TREND.

SEAS...THE WNA WAVEWATCH III MDL AND ECMWF WAM BOTH INITIALIZED
WELL OVER THE OFSHR WTRS VERSUS THE RA1 SEA STATE ANALYSIS. THE
MDLS BOTH APPEAR TO BE REASONABLE AND GENERALLY STAY WITHIN 1 TO 2
FEET OF EACH OTHER THRU THE ENTIRE FCST PERIOD...SO WILL GO WITH A
50/50 BLEND OF THE WNA WAVEWATCH III/ECWMF WAM FOR THE WAVE HT
GRIDS AS A COMPRIMISE SOLN.

EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

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

THE LTST GOES VIS IMGRY INDC A WK FRNTL BNDRY JUST E OF THE SRN
OFSHR WTRS...AND HIGH PRES BUILDING OVER THE SRN OFSHR WATERS.
THE 14Z ASCAT PASS FM THIS MORNING STILL INDC 20 KT...MAINLY IN
SRN NT2. CRNT SFC RPRTS INDC ABT THE SAME...10 KT OR LESS OVER THE
N PORTION OF THE OFSHR WATERS UNDER THE HIGH PRES RIDGE. THE 12Z
GFS 10M WINDS ARE INIT OK WHEN COMPARED WITH THE DATA...AND INDC
THE WINDS WL RMN NRLY THE SAME AS THE FRONT E OF THE AREA SLOWLY
DRIFTS W TWD THE AREA AS THE HIGH SHIFTS E OF THE AREA. THE 12Z
GLBL AND RGNL MDLS AGREE WELL WITH THE GFS IN THE SHORT TERM ON
THE MAIN SYNOP FEATURES...AND THE GFS HAS BEEN FAIRLY CONSISTENT
FOR THE PAST FEW DAYS. THE PREV FCST FLWD THE GFS IN THE SHORT
TERM...SO PLANNING ON USING THE 12Z RUN IN THE NEXT FCST.

LATE THU INTO FRI...THE 12Z GFS INDC ANTHR FRNTL BNDRY WL PASS
THRU THE NT1 WTRS...AND HAS BEEN CONSISTENT WITH THE TMG AND
INTNSTY OF THE FRONT AND WINDS. THE GFS ALSO AGREES WELL WITH THE
THE 12Z MDLS...ALTHO THE 12Z GEM CONT TO BE A PROGRESSIVE
OUTLIER...BUT HAS TRENDED A LTL SLOWER IN ITS 12Z RUN AND IS
CLOSER TO THE REST OF THE 12Z GUID. HOWEVER...THE 12Z GFS INDC 25
KT IN THE GULF OF MAINE...IN THE SW FLOW AHD OF THE CD FNT. CRNT
BUOY RPRTS INDC SSTS NR 70 DEG IN NT1...SO THE NORMALLY SUPPRESSED
MIXING IN SW FLOW MAY NOT BE AS SUPRESSED MUCH WITH THE STATIC
STABILITIES A LTL LOWER THAN USUAL. HOWEVER...THE MDL STABILITIES
STILL INDC THAT THE MXG WL BE LIMITED...AND WITH THE 12Z
ECMWF/UKMET INDCG 15 TO 20 KT MAX IN THE GULF OF MAINE IN THE SW
FLOW...PLANNING ON CAPPING WINDS AT 20 KT.

IN THE EXTENDED...THE 12Z ECMWF/GFS/GEM SOLNS ALL INDC HIGH PRES
BUILDS OVER THE OFSHR WATERS...AS A THIRD CDFNT MOVES INTO THE W
ATLC. THE GFS AND GEM ARE IN DECENT AGRMT WITH THE TMG...AND THE
ECMWF IS A LTL SLOWER. THE 12Z UKMET IS A SLOW OUTLIER...SO WL BE
DISREGARDING FOR THIS FEATURE. FOR THE WINDS...THE GFS KEEPS THEM
GENLY 15 KT OR LESS...WHICH SEEMS RSNBL...SO FAVORING THE GFS
ATTM. TO THE S OF THE OFSHR WTRS...THE 12Z MDLS INDC THAT A PAIR
OF TROPICAL SYSTEMS WL APRCH THE OFSHR WTRS...GASTON FROM THE SE
AND THE CRNT AREA OF DISTURBED WX ALONG A TRPCL WAVE NR PUERTO
RICO WL APRCH FM THE S. THE MDLS DISAGREE ON THE DVLPMT OF THE
TRPCL WAVE TO THE S...AND THE GFS BRINGS THE LOW UP THE COAST OF
FL TO JUST S OF THE NT2 WATERS BY THE END OF THE FCST PD. THE GFS
IS A BIT OF AN OUTLIER...AND INDC WINDS INCSRG TO 20 KT IN SRN
NT1. AS A RESULT...PLANNING ON CAPPING WINDS AT 15 KT IN SRN
NT2...BUT WL OTRW FAVOR THE GFS AS IT SUPPORTED BY THE OTHER 12Z
SOLNS ON ALL OTHER FEATURES.

SEAS...THE 12Z WAVEWATCH III AND ECMWF WAM BOTH INITIALIZED WELL
OVER THE OFSHR WTRS WHEN COMPARED WITH CRNT DATA AND THE RA1 SEA
STATE ANALYSIS...WHICH SHOW SEAS UP TO 6 FT CRNTLY IN THE OFSHR
WTRS. BOTH MDLS LOOK REASONABLE AND GENERALLY STAY WITHIN 1 OR 2
FEET OF EACH OTHER THRU MOST OF THE FCST PERIOD...SO WILL USE A
50/50 BLEND OF THE TWO SOLNS AS A COMPRIMISE SOLN. HOWEVER...WL
TONE DOWN SLIGHTLY IN SRN NT2 MON INTO MON NGT...AS THE
AFOREMENTIONED OVERDONE GFS WINDS IS REFLECTED IN THE WAVEWATCH.

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

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER SCOVIL/KELLS. OCEAN PREDICTION CENTER.



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