Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 220048
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
848 PM EDT THU AUG 21 2014

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

A WEAK LOW PRES CENTER SE OF GEORGES BANK CONTS TO DRIFT OFF TO
THE E WITH MAX ASCD WINDS (MAINLY PER AN EARLIER ASCAT PASS) GNRLY
IN THE 15-20 KT ACRS THE NE MOST NT2 WTRS AS PREVLY EXPECTED.
ELSWHR THRUT THE RMNG OFSHR AND CSTL WTRS THE ONLY SIG FEATURE IS
A WEAK STNRY FRONT ACRS THE CNTRL NT2 WTRS WHICH HAS WEAK ASCD
GRADIENTS PERSIST WITH ASCD WINDS ONLY IN THE 10-15 KT...OR
LESS...RANGE.

OVER THE SHORT TERM...THE LATEST MDLS CONT TO FCST THE WEAK LOW TO
CONT OFF TO THE E THRU FRI WITH NO SIG CHNGS IN THE WINDS THRUT
THE WTRS. THEN FRI NITE INTO SAT NITE WL FAVOR THE 12Z/18Z GFS AND
12Z UKMET/ECWMF SOLUTIONS WHICH ARE SMLR IN FCSTG THE FRONT TO
SLOWLY DRIFT S ACRS THE NT2 WTRS WHL SVRL WEAK FRONTAL LOWS RACE E
ALONG THE FRONT CAUSING A MOD STRONG (MAINLY 15-20 KT) ENE
GRADIENT TO DVLP N OF THE FRONT THRUT THE NT2 AND SRN NT1 WTRS. SO
BASED ON THE 18Z GFS/NAM SEE NO REASON TO REPOPULATE THE PREVLY
USED 12Z GFS 30M BL WINDS THRU SAT NITE AND WL JUST MAKE SM MINOR
EDITS MAINLY IN DEFERENCE TO THE 12Z ECMWF.

IN THE LONG RANGE...THE LATEST GLOBAL MDLS FCST LTL CHNG IN THE
PATTERN SUN/SUN NITE SO WL CONT WITH THE 12Z GFS 30M BL WINDS FOR
THE MOD ENELY GRADIENT. THEN BY LATE MON INTO TUE NITE THE
DISPARITY BTWN THE LATEST GLOBAL MDLS BCMS SIGNIFICANT DUE TO
THEIR FCST TRACKS OF THE NEXT POTENTIAL TROPICAL CYCLONE. THE 12Z
ECMWF/NAVGEM ARE BOTH SMLR IN FCSTG THIS PSBL TROPICAL CYCLONE TO
APRCH THE SE MOST NT2 WTRS LATE MON/MON NITE...THEN TURN NW INTO
THE CNTRL NT2 WTRS BY LATE TUE/TUE NITE WITH GALE FORCE ASCD BL
WINDS. THE 12Z ECENS MEAN INDICATES THAT THE 12Z ECMWF TRACK MAY
BE TOO FAR N. ON THE OTHER HAND THE 12Z GEM/UKMET KEEP THEIR
POTENTIAL CYCLONES TRACKING SIGLY FURTHER S AND PASSING W INVOF
SRN FLORIDA TUE/TUE NITE. IN BETWEEN THESE FCST TRACKS LIES THE
12Z/18Z GFS FCST TRACKS WHICH KEEP THEIR CYCLONE SE OF THE NT2
WTRS THRU LATE TUE/TUE NITE WHICH IS NOT FAR FM THE LATEST WPC/NHC
MEDIUM RANGE GUIDANCE. THE PREV OFSHR FCST PACKAGE USED THE 06Z
GFS 30M BL WINDS FOR MON THRU TUE NITE TIME FRAME. THEREFORE SINCE
THE 18Z GFS SOLUTION IS SMLR FOR THIS TIME FRAME AND IN LINE WITH
THE LATEST WPC/NHC GUIDANCE IN THE LONG RANGE...AND DUE TO THE
CURRENT MDL DISPARITY FOR THE POTENTIAL TROPICAL CYCLONE...FOR NOW
DO NOT PLAN ON REPOPULATING OUR FCST WINDS GRIDS FOR MON THRU TUE
NITE. SO OVERALL NO MAJOR LONG RANGE CHNGS ARE PLANNED FOR THE
NEXT OFSHR FCST PACKAGE.



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

12Z GLOBAL MODELS IN GOOD AGRMT THRU SHORT TERM...WITH SOME
DIFFERENCES NOTED IN THE EXTENDED TIME PERIOD. WILL POPULATE WIND
GRIDS WITH 30M WINDS FROM THE 12Z GFS THRU 12Z MON...THEN USE 30M
WINDS FROM THE 06Z GFS THEREAFTER.

LOW PRES NR 38N65W MOVING AWAY FROM THE OFFSHR WATERS. ASSOC COLD
FRONT ABOUT STATIONARY ACROSS THE CNTRL NT2 WATERS. MODELS SHOWING
BOUNDARY STATIONARY THRU TONIGHT...THEN SLOW MOVING SELY ACROSS
THE CTNRL NT2 WATERS FRI AND FRI NIGHT...AND INTO THE SRN NT2
WATERS SAT THRU SUN...THEN S OF THE AREA BY SUN NIGHT. NELY FLOW
THEN SETS UP ACROSS MOST OF THE OFFSHR WATERS SUN NIGHT THRU MON
NIGHT AS HIGH PRES BUILDS ACROSS THE NRN NT1 WATERS. WENT WITH 30M
WINDS DURING THIS TIME PERIOD AS MODELS TEND TO UNDERDO THE NELY
FLOW...ESP NEAR THE GULF STREAM.

SOME UNCERTAINTY REMAINS TOWARDS THE END OF THE FCST DUE TO A
POTENTIAL TROPICAL SYSTEM MOVING TOWARDS THE REGION. LATEST GLOBAL
MODELS NOT IN GOOD AGRMT ON THE TRACK AND TIMING OF THE
SYSTEM...WITH THE 00Z ECMWF BEING THE FASTER OF THE MODELS...WHILE
THE 12Z UKMET KEEPS THE SYSTEM SWRD TOWARDS SRN FLA. 12Z GFS IS
SLOWER WITH THE SYSTEM THAN ITS 06Z RUN. WILL GO WITH 06Z GFS FOR
NOW...WHICH IS A GOOD COMPROMISE BETWEEN THE FASTER 00Z ECMWF AND
THE SLOWER 12Z GFS RUN...AND IS SIMILAR TO THE THINKING ON THE
TROPICAL MED RANGE CALL WITH NHC AND WPC. NEEDLESS TO SAY...LOW
CONFDC IN THIS PORTION OF THE FCST.

.SEAS...WNA VERSION OF WWIII WITHIN A FT OR TWO OF CURRENT OBS.
WILL POPULATE WAVE GRIDS WITH 12Z WNA THRU 12Z MON...THEN 06Z WNA
THEREAFTER TO GO ALONG WITH THE 06Z GFS WINDS. WILL MAX OUT SEAS
AT 10 FT ON DAY 5.

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

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER VUKITS/ACHORN. OCEAN PREDICTION CENTER.


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