Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 301335
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
935 AM EDT SAT 30 APR 2016

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

GALES SHOULD SHIFT SE OF THE OUTERMOST ANZ910 WATERS WITHIN NEXT
COUPLE HOURS AND WILL DROP GALE WARNINGS WITH NEXT NT2 ISSUANCE
AT 15Z. WINDS WILL DIMINISH THROUGH THE DAY TODAY AS A HIGH PRES
RIDGE SLOWLY MOVES E ACROSS THE NEW ENGLAND AND MID ATLC
OFFSHORE WATERS TODAY THROUGH SUN. 06Z GFS WAS THEN FURTHER N
THAN ITS PREVIOUS RUN WITH THE SURFACE LOW TRACK THROUGH THE NEW
ENGLAND WATERS MON INTO MON NIGHT...BUT STILL IS SLIGHLY S OF
THE 00Z ECMWF. ALSO 06Z GFS WAS A BIT DEEPER WITH LOW AND
STRONGER WITH THE ASSOCIATED WINDS. THERE REMAINS FORECAST
UNCERTAINTY WITH HOW WIDESPREAD GALES MIGHT BE OVER EASTERN NEW
ENGLAND AND NORTHEASTERN MID ATLC WATERS MON AND MON NIGHT. 06Z
GFS AND 00Z ECMWF/UKMET INDICATING THAT GALES COULD DEVELOP OVER
GEORGES BANK AND THE GULF OF MAINE N ANE NE OF THE WARM FRONT
MON. DO NOT HAVE THE NECESSARY FORECAST CONFIDENCE TO ADD GALES
HERE AT THIS TIME...SO WILL NOT MAKE ANY CHANGES TO PREVIOUS
WIND GRIDS MON/ MON NIGHT. AS NOTED BELOW THE OVERNIGHT MODEL
RUNS SHOWED VERY LITTLE RUN TO RUN CONSISTENCY WITH THE
AMPLIFIED UPPER TROUGH/ CLOSED UPPER LOW MOVING INTO THE EASTERN
US LATE WED/THU. AGAIN WILL NOT BE MAKING ANY ADJUSTMENTS TO
PREVIOUS WIND GRIDS WHICH WERE MOSTLY BASED ON 00Z ECMWF.

WAVE HEIGHTS OVER INNER WATERS S OF NEW ENGLAND EXENDING S TO
NEAR CAPE HATTERAS ARE 1 TO 2 FT HIGHER THAN THE 06Z WAVEWATCH
III AND 00Z ECMWF WAM. UPDATED THE NEAR TERM WAVE HEIGHT GRIDS
BASED ON THESE LATEST OBS.

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

OVER THE SHORT TERM...THE LATEST ASCAT SCATTEROMETER PASSES HV
MISSED THE STRONGEST PORTION OF THE NELY GRADIENT TO THE NW OF
THE SFC LOW NOW JUST E OF THE CNTRL NT2 WTRS. BUT PER THEIR
EARLIER 25-30 KT RETRIEVALS JUST OUTSIDE THIS AREA AM CONFIDENT
THAT GALES ARE NOW PRESENT IN THE VCNTY OF THE GULF STREAM IN
NT2 ZONES ANZ920 AND ANZ910. WITH THIS IN MIND WULD FAVOR THE
SLIGHTLY STRONGER 00Z NAM/GFS/GEM SOLUTIONS FOR THIS SFC LOW
TODAY INTO TONITE AS THE MDLS ALL FCST THE LOW TO MOV OFF TO THE
E WITH THE GRADIENT IN ITS WAKE WKNG. THEREFORE PLAN ON
POPULATING OUR FCST WIND GRIDS WITH THE REPRESENTATIVE 00Z GFS
30M BL WINDS FOR TODAY AND TONITE.

THEN SUN/SUN NITE...THE 00Z MDLS IN GNRL AGREE THAT A WARM FRONT
WL LIFT NNE FROM THE CNTRL/NRN NT2 WTRS INTO THE SRN NT1 WTRS
WITH AN ASCD SFC LOW MOVG NE OFF THE NRN MID ATLC AND INTO THE
SRN NT1 WTRS SUN NITE. OVERALL WULD FAVOR THE SLIGHTLY LESS
PROGRESSIVE 00Z NAM/GFS/ECMWF SOLUTION FOR THIS FROPA VS THE 00Z
GEM/UKMET. THEREFORE WL TRANSITION TO POPULATING WITH THE MR
REPRESENTATIVE 00Z GFS 10M BL WINDS ON SUN/SUN NITE.

IN THE LONG RANGE...THE 00Z MDLS IN GNRL AGREE THAT THE FRONTAL
LOW WL TRACK NE ACRS THE NT1 WTRS MON AND THEN CONT NE TO NOVA
SCOTIA BY TUE MORNING. IN RGRDS TO THE FCST TRACK OF THIS
LOW...THE 00Z GEM/ECMWF ARE NOW ON THE NRN FRINGE OF THE MDL
TRACK ENVELOPE WHL THE 00Z NAM/GFS/UKMET HV CONVERGED TWDS VERY
SMLR MR SRN TRACKS. SINCE IT RMNS MR CONSISTENT AND ALSO HAS THE
SPRT OF THE 00Z GEFS MEAN...WL ACPT THE 00Z GFS FCST TRACK FOR
THIS LOW. IN RGRDS TO THE ASCD FCST GRADIENTS WITH THIS
LOW...BELIEVE THE 00Z GFS LOOKS LIKE A RSNBL COMPROMISE BTWN THE
STRONGER 00Z NAM/GFS AND WEAKER 00Z UKMET/ECMWF SOLUTIONS.
THEREFORE WL CONT TO POPULATE WITH THE 00Z GFS 10M BL WINDS MON
INTO MON NITE...WITH SM ADDITIONAL FURTHER EDITS NR THE GULF
STREAM ACRS THE OUTER NE NT2 WTRS TO MAINTAIN THE PREVLY FCSTD
PSBL GALES.

THEN FURTHER OUT IN THE LONG RANGE...THE DISPARITY BTWN THE 00Z
GLOBAL MDLS BCMS SIGNIFICANT. VS ITS PREV 18Z RUN WHICH FCST A
DVLPG SFC LOW TO MOV NE OFF THE MID ATLC COAST TUE NITE AND THEN
TRACK NE ACRS THE NRN NT2 AND THEN SERN NT1 WTRS WED/WED
NITE...THE 00Z GFS HAS NOW COMPLETELY BACKED OFF AND FCSTS NO
SFC LOW AT ALL MOVG OFSHR EVEN THO IT FCSTS A SHARPER UPR TROF
TO DIG INTO THE ERN CONUS WED NITE. ON THE OTHER HAND THO LESS
PROGRESSIVE THAN ITS PREV 12Z RUN...THE 00Z GEM STIL FCSTS A SIG
DVLPG SFC LOW TO TRACK NNE OFF THE MID ATLC AND NEW ENGLD COASTS
WED/WED NITE. THE 00Z UKMET/ECMWF NOW ALSO FCST A SIGLY MR
AMPLIFIED UPR LVL PTRN TO DVLP WITH AN ASCD DVLPG SFC LOW MOVG
OFF THE SE COAST WED NITE WITH GALE FORCE ASCD BL WINDS DVLPG.
SO FOR NOW WITH VERY LOW FCST CONFIDENCE...WL TRANSITION TO
POPULATING WITH THE 00Z ECMWF BL WINDS ON LATE MON NITE THRU WED
NITE. BUT DUE TO THE CURRENT MDL DISPARITY...WL CAP THESE WINDS
BELOW GALE FORCE ON WED NITE TO HOLD OFF ON FCSTG ANY PSBL WRNGS
FOR NOW.

SEAS...THE 00Z WAVEWATCH III HAS INITIALIZED SLIGHTLY BETTER
THAN THE 00Z ECMWF WAM. WITH THIS IN MIND AND SINCE THE 00Z GFS
WL BE FAVORED...WL POPULATE OUR FCST WAVE GRIDS WITH THE 00Z
WAVEWATCH III FOR TODAY INTO MON NITE. THEN SINCE THE 00Z ECMWF
WL THEN BCM THE FAVORED SOLUTION...WL TRANSITION TO THE 00Z
ECMWF WAM FCST SEAS LATER MON NITE THRU WED NITE.

.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...
     GALE POSSIBLE MON.
.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...
     GALE POSSIBLE MON.
.ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N...
     GALE POSSIBLE MON INTO MON NIGHT.

$$

.FORECASTER CLARK/VUKITS. OCEAN PREDICTION CENTER.



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