Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 290030
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
830 PM EDT SUN AUG 28 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 T.D. EIGHT CENTERED ABOUT 80
NM SE OF THE SRN NT2 WTRS...WITH T.D. NINE CENTERED IN THE FLORIDA
STRAITS JUST S OF KEY WEST...AND HURCN GASTON CENTERED ABOUT 500
NM E SE OF BERMUDA. REFER TO LATEST NHC ADVISORIES FOR ADDITIONAL
INFORMATION ON T.D. EIGHT/T.D. NINE/HURCN GASTON. LATEST AVAILABLE
ASCAT AND ASCAT HI-RES PASSES FROM THIS MORNING SHOW 25 TO 30 KT
WINDS ON THE WRN SIDE OF T.D. EIGHT JUST E OF THE SRN NT2
WTRS...WITH A LARGER AREA OF WINDS TO 20 KT OVER ZONES 920 AND 930
IN THE NT2 WTRS. LIGHTNING DENSITY PRODUCT DATA AT 2310Z SHOWS
SOME SCATTERED SHOWERS ON THE WRN SIDE OF T.D. EIGHT.

MODELS...REGARDING T.D. EIGHT THE ECMWF/GFS/UKMET ARE IN GUD
AGREEMNT WITH ITS TRACK ACROSS THE OFSHR WTRS...WHILE THE GEM
BECOMES SIGNIF FASTER WITH IT DURING THE THU INTO FRI TIMEFRAME.
GEM/UKMET BECOME MUCH STRONGER WITH T.D. EIGHT OVER THE WED INTO
FRI PERIOD...BUT AM NOT READY TO GO AGAINST THE ECMWF/GFS ATTM AND
THUS WILL GO WITH THE REPRESENTATIVE GFS SOLN. REGARDING T.D.
NINE THE GEM LOOKS LIKE AN OUTLYER SOLN SINCE IT TAKES THE SYSTEM
INLAND OVER SE CONUS FOR LATE THRU THRU FRI NITE...AND THE ECMWF
ALSO LOOKS LIKE AN OUTLYER SOLN BECAUSE IT IS SIGNIF WEAKER THAN
THE OTHER MDLS WITH T.D. NINE. THE GFS LOOKS LIKE AN EXCELLENT
MEDIAN MDL SOLN FOR T.D. NINE SINCE IT IS IN BETWEEN THE FASTER
ECMWF AND SLOWER UKMET. SO A BOOSTED VERSION THE GFS 30M SOLN
WILL BE USED FOR THE WIND GRIDS THRU THE ENTIRE FCST PERIOD. IF
THERE ARE NO MAJOR CHANGES TO THE FCST TRACKS FOR T.D. EIGHT AND
T.D. NINE...THEN DO NOT ANTICIPATE MAKING ANY SIGNIF CHANGES TO
THE CURRENT FCST TREND.

SEAS...BOTH THE WNA WAVEWATCH III MDL AND ECMWF WAM INITIALIZED
REASONABLY WELL OVER THE OFSHR WTRS. WNA WAVEWATCH III LOOKS
UNDERDONE WITH SEAS AROUND THE BOTH OF THE TROPICAL CYCLONES...AND
ECMWF WAM IS EVEN MORE UNDERDONE ESPECIALLY WITH T.D. NINE FRI AND
FRI NITE. SO WILL USE THE WNA WAVEWATCH III MDL FOR THE WAVE HT
GRIDS THRU THE FCST PERIOD...BUT WILL BOOST IT UP AROUND T.D.
EIGHT AND T.D. NINE AS THEY CROSS THE OFSHR WTRS.

EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

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

THE SAT IMG INDC HIGH PRES RIDGE OVER THE NRN WATERS. THE
OBSERVATIONS INCLUDING ASCAT ABOUT 1515Z SHOW HIGHER WINDS OVER
S-ERN PARTS. AT 18Z STATIONARY FRONT LIES ACROSS THE CENTRAL
WATERS AND THE PRES GRADIENT IS FAIRLY SLACK OVER MOST OF THE
FORECAST WATERS. TROPICAL DEPRESSION EIGHT JUST E OF THE SRN
WATERS WILL MOVE WNW ACROSS THE WATERS TWD THE SC COAST. SEE THE
NHC FOR MORE AND LATEST INFORMATION ON TD EIGHT. THE MODELS HAVE
INITIALIZED JUST OK THE 18Z OBSERVATIONS AND THEY HAVE SOME
DIFFERENCES ON THE PATH AND STRENGTH OF TD EIGHT IN THE SHORT
TERM. GFS AND ECMWFHR HAVE TD EIGHT MOVING TWD THE SC COAST AND SO
ARE CMC/UKMETHR BUT THE LATER INDC MUCH STRONGER SYSTEM AS IT
MOVES NE AND PASSES THRU THE BALT CANYON. FOR THE 12Z RUN GFS NOW
HAS WINDS LESS THAN THE ASCAT BY 5 KT IN THE N SECTOR OF THE
DEPRESSION WHERE THE ASCAT SUGGESTED HIGHER WINDS WITH CMC AND
UKMETHR BEING LESS BY 10 KT. THE OTHER DIFFRENCES ARE ON ANOTHER
SYNOP SYSTEM THAT HAS POTENTIAL TO MOVE INTO THE SRN WATERS FROM
THE GULF OF MEXICO IN THE EXTENDED PERIOD. IN ADDITION...
GFS/CMC/UKMETHR/ECMWFHR/NOGAPS/JMA MODELS HAVE NOT AGREED WELL ON
THE OTHER LOWS THAT WILL DEVELOP AND IMPACT THE WX OVER THE WATERS
IN THE EXTENDED PERIOD. WITH ALL THE DIFFERENCES AMONG THE MODELS
WILL POP GRIDS WITH GFS JUST AS THE BASIS AND THEN ADJUST THE
WINDS ESPECIALLY IN AREAS IN THE VICINITY OF TD EIGHT.

.SEAS...THE SEAS RANGE BETWEEN 2 AND 6 FT ACROSS THE WATERS AND NWW3
MULTI GRID FITS WELL WITH THE OBSERVED SEAS PATTERN EXCEPT IN
AREAS AROUND TD EIGHT. NWW3 IS ALSO CLOSE TO THE ECMWFWAVE MODEL.
BOTH WAVE MODELS ARE UNDERDONE NEAR AND AROUND THE TROPICAL
DEPPRESION AND SO WILL ADJUST SEAS AROUND THE TD. OTHERWISE WILL
START OF WITH NWW3 AS THE MAIN WAVE MODEL GUIDANCE.

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

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
.ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL...
     TROPICAL STORM POSSIBLE WED.
.ANZ828...INNER WATERS FROM CAPE CHARLES LIGHT TO CURRITUCK BEACH LIGHT...
     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED.
.ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON...
     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED.
.ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS...
     TROPICAL STORM TUE.
     TROPICAL STORM POSSIBLE TUE NIGHT.
.ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR...
     TROPICAL STORM MON NIGHT INTO TUE.
     TROPICAL STORM POSSIBLE TUE NIGHT.
.ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR...
     TROPICAL STORM MON INTO TUE.
     TROPICAL STORM POSSIBLE TUE NIGHT.
.ANZ835...INNER WATERS FROM CAPE FEAR TO 31N...
     TROPICAL STORM POSSIBLE FRI INTO FRI NIGHT.
.ANZ935...OUTER WATERS FROM CAPE FEAR TO 31N...
     TROPICAL STORM MON INTO MON NIGHT.

$$

.FORECASTER SCOVIL/MUSONDA. OCEAN PREDICTION CENTER.



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