Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 070052
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
752 PM EST FRI MAR 6 2015

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

A HIGH PRES RIDGE EXTENDING ACRS THE SRN NT1 WTRS IS MAINTAINING A
REL QUIET PATTERN ACRS THE REGION. TO ITS S THE RIDGE IS SPRTG A
MOD STRONG (UP TO PRIMARILY 20-25 KT) NELY GRADIENT ACRS THE
CNTRL/SRN NT2 WTRS. MAX SEAS ARE ALSO OVER THESE WTRS IN THE 7-11
FT RANGE WHICH ARE BEING EQUALLY WELL BY THE 18Z WAVEWATCH III AND
12Z ECMWF WAM MDLS AT THE MOMENT.

OVER THE SHORT TERM...THE LATEST MDLS ARE IN GOOD AGRMT THAT THE
RIDGE WL SINK S ACRS THE NT2 WTRS THRU SUN WITH CONDS RMNG LITE IN
ITS VCNTY. S OF THE RIDGE THE 18Z GFS RMNS CONSISTENT VS ITS PREV
RESPECTIVE RUNS IN FCSTG A WEAK LOW TO PASS ACRS THE NRN NT1 WTRS
SUN WHL PULLING A COLD FRONT OFSHR. INADVOF THIS FRONT THE 18Z GFS
CONTS TO FCST SM GALE FORCE BL WINDS TO DVLP ACRS THE NE NT2 WTRS
SUN AFTERNOON SMLR TO ITS PREV 12Z RUN AND THE 12Z/18Z NAM/12Z
GEM. BUT WITH THE 12Z NAVGEM/UKMET/ECMWF FCSTG WEAKER GRADIENTS WL
CONT TO GO WITH THE PREVLY USED 12Z GFS/ECMWF BLEND AND KEEP WINDS
SUBGALE. SO OTHERWISE NO SIG SHORT TERM CHNGS ARE PLANNED TO THE
PREV OFSHR FCSTS.

IN THE LONG RANGE...ON MON IN THE WAKE OF A SCNDRY COLD FROPA OR
SFC TROF THE 18Z GFS...SMLR TO THE 12Z GFS/GEM...FCSTS A STRONGER
WNWLY GRADIENT TO DVLP ACRS THE NT1 AND NRN NT2 WTRS THAN THE
OTHER MDLS. AGAIN BLV THE PREVLY USED 12Z GFS/ECMWF SOLUTION LOOKS
LK A RSNBL COMPROMISE FOR THIS GRADIENT. THEN TUE NITE/WED THE
DISPARITY BTWN THE LATEST GLOBAL MDLS INCREASES IN RGRDS MAINLY TO
THE FCST TRACK/TIMING OF A SRN STREAM DVLPG SFC LOW FCST TO TRACK
NE ACRS NT2 WTRS. OVERALL TO BE MR IN LINE WITH THE LATEST WPC
MEDIUM RANGE GUIDANCE WULD FAVOR A COMPROMISE 12Z UKMET/ECMWF
SOLUTION FOR THIS SYSTEM. PER THIS COMPROMISE AM TEMPTED TO ADD
PSBL GALES TO THE OUTER CNTRL/NERN NT2 WTRS ON TUE NITE...WHICH
ARE ALSO INDICATED BY THE 12Z/18Z GFS. BUT FOR NOW DUE TO THE
CURRENT MDL DISPARITY WL HOLD OFF ON FCSTG GALES AND WL SEE IF THE
00Z MDLS LATER COME INTO BETTER AGRMT. SO OVERALL PLAN ON MAKING
ONLY GNRLY MINOR LONG RANGE CHNGS IN THE NEXT OFSHR FCST PACKAGE.


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


MODELS ARE IN GOOD AGREEMENT ON THE GENERAL PATTERN OVER THE NEXT
FIVE DAYS...BUT QUITE A BIT ON THE DETAILS. TODAYS 12Z MODEL RUNS
ARE IN A LITTE BTTR AGRMNT OVER PRVS RUNS.

FOR THE SHORT TERM FCST...MOD NE WINDS OFF THE SE COAST WILL
GRADU DMNSH TNGT AS LRG HIGH PRES OVER THE CNTNTL U.S. SLIDES
E...AS DOES THE COLD FRONT JUST E OF THE SRN WATERS. FOR TNGT...
THE GFS SEEMS TO HAVE SOME GRID SCALE FEEDBACK NEAR EASTERNMOST
HTTRS CANYON AND DVLPS A WK SFC LOW 200 NM E OF CAPE HTTRS BY 06Z.
THE AFFECT OF THIS IS TO ARTIFICALLY ENHANCE THE N TO NE GRADIENT
OVR THE STHRN WATERS. THE OTHER MODELS SHOW SOME TROFINESS...BUT
ONLY THE GFS DVLPS A CLOSED SFC LOW...AS STRNG HIGH PRES BUILDS IN
FM THE W. WILL EITHER SMOOTH OUT THE GFS GRIDS TO FIX THE WIND
DRCTN TNGT AND LOWER THE WINDS BY ABT 5 KT...OR MORE LIEKLY BLEND
IN THE ECMWF.

NEXT FCST FEATURE IS WEAK SFC LOW WITH DVLPNG COLD FRONT FCST TO
MOVE OFF THE COAST OF MAINE EARLY SUN. THE GFS IS SLGTLY FASTER
THEN THE ECMWF/UKMET...AND THE NAM IS A MUCH FASTER AND WEAKER
OUTLIER. THE GFS ALSO DVLPS STRNGR WINDS IN THE W GRADIENT S OF
THE LOW CNTR SUN S OF GEORGES BANK...AND IS TRENDING WEAKER WITH
THE PAST TWO RUNS. PREFER...TO BLEND THE GFS AND ECMWF TO SMOOTH
OUT THE MODELS DETAILS. FOR SUN NIGHT AND MON...MODELS DFFR SLGTLY
ON DVLPG LOW E OF GEORGES BANK AND SHAPE OF RIDGE BUIDING E TO THE
COAST. AGAIN...NO ONE MODEL STANDS OUT AS A CLEAR CHOICE. THE
RESULT OF CONTG TO BLEND THE GFS AND ECMWF GIVE A WIND FEILD
SUFICIENTLY CLOSE TO BOTH.

TUE...THE GFS IS A LTTL OVERDONE WITH DVLPNG LOW ALONG THE SE
COAST AS THE GFS DVLPS A GALE FRC GRADIENT. BY 00Z WED...THE ECMWF
AND UKMET BEGIN TO DIFFR FM THE GFS AND DVLP THE LOW CLOSER TO THE
SRN NEW ENGLAND WATERS. SNICE THE GFS HAS BN STRUGGLING WITH ANY
TYPE OF CONSISTENTCY HERE...WL FAVOR THE ECMWF...WHICH HAS SUPPORT
OF THE UKMET. ALSO...GEFS ENSMBL MEMBERS HINT MORE TWDS THE ECMWF
FCST. GALES ARE BRFLY PSBL S OF GEORGES BANK TUE NGT...BUT CNFDC
PRECLUDES RAISING THE WINDS ABV 30 KT ATTM. ANOTHER LRG HIGH PRES
WILL BUILD INTO WED NIGHT. THE NW GRADIENT MAY RESULT IN NW
GALES...BUT WL DTRM THIS AS THE EVENT GETS CLOSER. THE GFS/ECMWF/
UKMET AGREE ON TIMING OF THE ATTENDANT COLD FRONT FM THE ABOVE
LOW...AND IT IS FCST TO PUSH S WED AND WED NGT...MOVING S OF 31N
JUST BEFORE 12Z THU.

.SEAS...THE 12Z MULTIGRID WAVEWATCH III MODEL HAS INITIALIZED WELL
OVER THE OFFSHORE WATERS...EXCEPT OFF THE SE COAST WHERE SEAS ARE
UNDERDONE IN THE MODERATE NE FLOW BY ABT 2 FT. WL ADJUST THESE UP
FOR INIT CONDS. AS THE NE WINDS DMNSH TNGT INTO SAT... THE MODEL
SHLD PERFORM BTTR. AS WITH THE WIND GRIDS...WL USE A 50/50 BLEND
OF THE WAVEWATCH/WAM THRU 00Z TUE...THEN GO 100 PCT WAM AFTER
THAT.


.EXTRATROPICAL STORM SURGE GUIDANCE...THE ESTOFS BRFLY DVLPS A 1
TO 1.5 FT SURGE ALONG THE SRN MID ATLC COAST AND ALSO OFF THE SC
AND GS COAST EARLY TNGT...WHICH DMNSHS OVERNIGHT. THEN A NEG 1 TO
1.5 FT SURGE ALONG THE NJ COAST LATE TUE...DMNSHNG TUE NGT. SURGE
VALUES ON THE ETSS ARE LESS AND ARE PROBABLY MORE LIKELY GIVEN THE
FCST WINDS ARE A LTTL LESS THEN GFS GDNC...EXCEPT OFF THE SE COAST
EARLY TNGT.



.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER VUKITS/PROSISE. OCEAN PREDICTION CENTER.



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