Marine Interpretation Message
Issued by NWS

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000
AGNT40 KWNM 260057
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
857 PM EDT MON JUL 25 2016

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

LGTNG DENSITY PROD INDC STRONG TSTMS FROM EARLIER OVR NRN NT2 NEAR
N WALL OF GULF STREAM HAVE WEAKENED A BIT...AND GOES IR IMGRY
INDC CRNTLY OVR ZONE ANZ910 IN NE NT2. THE IMAGERY AND LGTNG DATA
INDC ANTHR ROUND OF TSTMS MOVG OFF THE MID ATLC COAST NEAR LONG
ISLAND...IN THE CONVERGENCE AHEAD OF A SFC TROF. THE PREV FCST
LOOKS IN LINE WITH THE WX GRIDS...SO NOT PLANNING ON MAKING ANY
CHAGES TO THEM.

OTRW...THE 12Z/18Z MDLS ALL INDC THE AFOREMENTIONED SFC TROF WL
MOVE INTO THE AREA TNGT...FLWD BY A FRNTL BNDRY CRNTLY ACRS THE
GREAT LAKES REGION...LATER TNGT INTO TUE NGT. THE CRNT SFC RPRTS
INDC WINDS CRNTLY UP TO 20 KT IN THE SW FLOW AHD OF THE FIRST
BNDRY...AND THE 12Z/18Z GFS 10M WNDS ARE INIT OK WHEN COMPARED
WITH THE DATA. THE GFS AGREES FAIRLY WELL WITH THE LTST
ECMWF/UKMET/NAM/GEM MDL RUNS WITH THE TMG OF THE BNDRY...AND INDC
THE WINDS WL INCRS TO 25 KT AS THE FRONT MOVES INTO THE
AREA...MAINLY OVER THE UNSTABLE ENVIRONMENT OVER THE GULF STREAM.
THE PREV FCST WENT WITH THE 12Z GFS IN THE FCST OVER THE SHORT
RANGE...AND ATTM SEE NO REASON TO DIVERT FROM IT AS IT IS
SUPPORTED BY OTHER GLOBAL/REGIONAL SOLNS.

THE BIGGEST FCST PROBLEM IS IN THE EXTENDED PD...AS THE GFS CONT
TO STAY A FAST OUTLIER WITH THE NEXT SYS ON FRI INTO SAT. THE 12Z
ECMWF IS STILL ABOUT THE BEST COMPROMISE SOLN WITH THE SPEED OF
THE SYS...BUT IS SLIGHTLY WKR THAN THE GFS/GEM SOLNS. ALSO GFS
TRENDED A LTL SLOWER IN THE 18Z RUN...IT IS STILL A LTL TOO FAST.
AS A RESULT...PLANNING ON STAYING WITH PREV LINE OF THINKING...AND
USING THE 12Z ECWMF WHILE BOOSTING THE WINDS. OTRW NOT PLANNING ON
MKG ANY SIG CHANGES FOR THE REMAINDER OF THE UPDATE PKG.

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

A 1430Z METOP-B ASCAT OVERPASS RETURNED 25 TO 30 KT WINDS INVOF
38.5N 72.5W ASSOCIATED WITH AREA OF STRONG CONVECTION LIKELY A
SUPERCELL WHICH HAS SINCE MOVED TO NEAR 37.5N 70.5W. LATEST
LIGHTNING DENSITY IS INDICATING CONVECTION HAS BECOME BETTER
ORGANIZED AS IT PASSED ACROSS THE N WALL OF THE GULF STREAM LAST
HOUR. SHIP REPORTED 40 KT NEAR THIS CONVECTION AT 18Z. THE 12Z
MODELS ARE IN GOOD AGREEMENT ACROSS THE EASTERN SEABOARD FOR THE
NEXT COUPLE DAYS...AND SHARE SIMILAR TIMING WITH A WEAK COLD
FRONT APPROACHING FROM THE NW TODAY...MOVING SE ACROSS THE NT1
WATERS TONIGHT/TUE...AND NRN NT2 WATERS TUE NIGHT. 12Z GFS 10M
WINDS ARE WELL SUPPORTED BY OTHER GUIDANCE WITH WINDS TO 20 OR
25 KT JUST S OF THIS FRONT. FRONT SHOULD THEN STALL AND WEAKEN
ACROSS THE NT2 WATERS AS SERIES OF WEAK LOWS PASS E ALONG FRONT
WED INTO THU.

BY THU NIGHT/FRI 12Z GLOBAL MODELS GENERALLY AGREE THAT ANOTHER
WEAK COLD FRONT WILL MOVE OFF THE NEW ENGLAND COAST. THE 12Z GFS
THEN BECOMES A PROGRESSIVE OUTLIER WITH A DEVELOPING SURFACE LOW
LATE FRI/SAT. 12Z GEFS ALSO SUGGESTING THAT IT IS TOO FAR S WITH
THE LOW TRACK. 12Z ECMWF WAS CONSISTENT WITH ITS PREVIOUS FEW
RUNS IN MOVING LOW THROUGH NT1 WATERS SAT INTO SAT NIGHT.
HOWEVER VERSUS ITS 00Z RUN THE 12Z ECMWF WAS A BIT
WEAKER...BACKING OFF FROM THE 30 KT WINDS SHOWN IN THE 00Z RUN.
12Z UKMET IS SLOWER THAN ECMWF BUT SUPPORTS THE MORE NRN
SOLUTION. AS A COMPROMISE FOR STRENGTH OF WINDS WILL USE A 50/50
BLEND OF THE PAST TWO RUNS OF THE ECMWF FRI THROUGH THE
WEEKEND...WHICH WILL ALSO BE VERY CLOSE TO LATEST WPC MEDIUM
RANGE GUIDANCE. ADDED 10 PERCENT TO THESE BLENDED TO GET SLIGHLY
MORE EXPANSIVE AREAS OF 25 KT WINDS ASSOCIATED WITH THE SURFACE
LOW AND SE OF ITS COLD FRONT SAT/SAT NIGHT.

.SEAS...OVERALL THE 12Z WAVEWATCH III AND 12Z ECMWF WAM MDLS HV
BOTH INITIALIZED THE CURRENT W ATLC WAVE HEIGHTS VERY WELL...AND
ARE IN GOOD AGREEMENT AT LEAST INTO FRI. WITH THE 12Z GFS BEING
FAVORED...PLAN ON POPULATING WAVE HEIGHT GRIDS WITH ALL 12Z
WAVEWATCH III FOR TODAY THRU THU NIGHT. THEN WITH PREFERENCE FOR
ECMWF BLEND POPULATED WITH 50/50 BLEND OF 00Z AND 12Z ECMWF WAM
FRI THROUGH THE WEEEKEND.

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


.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER KELLS/CLARK. OCEAN PREDICTION CENTER.


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