Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 260121
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
925 PM EDT THU 25 AUG 2016

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

GULF OF MAINE BUOYS HAVE BEEN REPORTING IN THE 15 TO 20 KT RANGE
FOR THE BETTER PART OF THE DAY TODAY WHILE ELEVATED MT DESERT
ROCK AND MATINICUS ROCK HAVE REPORTED 20 TO 25 KT. OVER THE NEAR
TERM THE PREVIOUS OPC WIND GRIDS MAY BE SHOWING TOO EXPANSIVE OF
AN AREA TO 20 KT HERE BUT OTHERWISE LOOK REASONABLE. TONED DOWN
THE HIGHER WIND GRIDS SLIGHLY OVER GULF OF MAINE/GEORGES BANK
FOR TONIGHT AND FRI. THE LATEST MODELS APPEAR TO HAVE ARRIVED AT
A BETTER CONSENSUS WITH THE TIMING OF THE WEAK COLD FRONT ACROSS
THE NT1 AND NRN/CENTRAL NT2 WATERS FRI NIGHT INTO SAT NIGHT. THE
PREVIOUSLY TIME SHIFTED 12Z GFS THEN STILL LOOKS GOOD FOR TIMING
OF NEXT COLD FRONT MON NIGHT THROUGH TUE NIGHT.

BUOY 44065 S OF WRN LONG ISLAND SUGGESTING THAT WAVE HEIGHTS
ACROSS S OF NEW ENGLAND WATERS ARE 1 TO 2 FT OR SO HIGHER THAN
BOTH THE 12Z/18Z WAVEWATCH III AND 12Z ECMWF WAM. WAVEWATCH III
MOVES THE LONG PERIOD SWELL ASSOCIATED WITH GASTON INTO THE ERN
MOST NT2 OFFSHORE WATERS SAT EVENING THEN NEW ENGLAND COAST SUN
AND MID ATLC COAST LATER SUN AND SUN NIGHT...WHICH IS ABOUT 12
TO 18 HOURS FASTER THAN THE ECMWF WAM. AT THIS TIME AM LEANING
TOWARD THE WW3 SOLUTION.

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

GOES WV IMGRY INDC A SOMEWHAT FLAT RIDGE OVER THE WRN ATLC AND A
SHORTWAVE TROF UPSTREAM MOVING INTO THE GREAT LAKE REGION. THE
LTST NCEP SFC ANALYS INDC A HIGH PRES RDG ACRS THE OFSHR WTRS
UNDER THE UPR RDG...A WK STNRY FRNTL BNDRY JUST E OF THE AREA NR
BERMUDA...AND A COLD FRONT INLAND OVER THE GREAT LAKES REGION
ASSOC WITH THE SHORTWAVE TROF MOVING E TWD NT1. 15Z ASCAT INDC
VARIABLE WINDS 5 TO 15 KT OVR THE N PTTN UNDER THE
RIDGE...EXCEPT OVER THE GULF OF MAINE WHERE THE ASCAT INDC SRLY
WINDS TO 20 KT AHD OF A WK LOW PRES TROF NEAR THE COAST. THE
ASCAT ALSO INDC NE FLOW OVR SRN NT1 TO THE W OF THE STNRY FRONT
E OF THE AREA. CRNT SFC RPRTS INDC WINDS TO 15 KT OVR NT1...AND
THE 12Z GFS WINDS WHICH ARE WELL INITIALIZED WHEN COMPARED WITH
THE CRNT DATA INDC THE INTNSTY OF WINDS ARE SLOWLY DECREASING AS
THE STNRY FRONT AND RIDGE ARE BOTH SLOWLY WEAKENING. THE 12Z
ECMWF/NAM/GEM/UKMET ALL INDC THE SAME TREND...SO ATTM PLANNING
ON REFLECTING MDL TRENDS AND WL SLWOLY DCRS THE WINDS IN SRN NT2
TNGT. ALSO...THE 12Z ECWMF/NAM/GEM/UKMET AGREE SOMEWHAT WELL
WITH THE GFS ON THE TMG OF THE COLD FRONT CRNTLY OVER THE GREAT
LAKES REGION...BUT THE NAM/GEM/GFS ARE A BIT STGR WTIH THE SW
WINDS AHD OF THE FRONT...RANGING BTWN 25 AND 30 KT. THE 12Z
ECMWF AND UKMET ARE WKR...AND INDC ONLY 15 TO 20 KT. BUOY
REPORTS CRNTLY INDC SSTS IN THE MID 60S TO 70 DEG F IN THE GULF
OF MAINE...AND THE 12Z GFS STABILITY INDICES INDC THAT THE
NORMALLY STABLE ENVIRONMENT OVER THE COLD SHELF WATERS IN THE
GULF OF MAINE IS NOT QUITE AS STABLE AS USUAL WITH THE WARMER
SSTS IN PLACE. HOWEVER...WITH THE GFS INDCG ONLY ABT 25 TO 30 KT
IN SW FLOW AT 925 MB...THE VERT SHEAR LOOKING LIMITED...AND
MODEL STABILITY INDICES INDICATING ONLY MARGINAL
INSTABILITY...AM THINKING THAT 25 KT AND HIGHER SFC WINDS ARE
OVERDONE. AS A RESULT...PLANNING ON CAPPING WINDS AT 20 KT IN
THE NEXT PKG.

OTRW...THE 12Z GFS INDC HIGH PRES WL BUILD OVER THE AREA ON SAT
AND SUN AFTER THE WK CD FRONT MOVES E OF THE REGION. THE 12Z
MDLS HAVE BEEN IN SOMEWHAT DECENT AGRMT ON ANOTHER WK FRONT MOVG
INTO NT1 MON...WITH SOME DIFFS ON THE TMG. THE 12Z ECMWF HAS
TRENDED SLIGHTLY FASTER FM THE 00Z...AND IS NOW A LTL FASTER
THAN THE CONSISTENT 12Z GFS. THE 12Z GEM HAS TRENDED TWD THE
GFS...BUT THE 12Z UKMET IS THE PROGRESSIVE SOLN...SO THERE IS A
FAIR AMT OF UNCERTAINTY ON THE TMG. THE PREV FCST FAVORED THE
GFS...SO PLANNING ON FAVORING IT IN THE NEXT FCST...BUT PLANNING
ON TIME SHIFTING IT TO MAKE IT A LTL FASTER IN DEFERENCE TO THE
UKMET/ECMWF SOLNS. HOWEVER...THE 06Z GFS HAS NOT CHANGED MUCH FM
THE PREV RUN...WHICH WAS USED IN THE PREV FCST...SO ATTM
PLANNING ON STAYING WITH CONTINUITY FOR THE REMAINDER OF THE
FCST PD.

SEAS...THE 12Z WAVEWATCH AND ECMWF WAM MDLS HAVE BOTH
INITIALIZED WELL OVER THE OFSHR WTRS WHEN COMPARED WITH THE RA1
SEA STATE ANALYSIS AND SFC RPRTS. THE MDLS BOTH LOOK REASONABLE
IN THE SHORT RANGE... AND GENERALLY STAY WITHIN 1 TO 2 FEET OF
EACH OTHER THRU THE SHORT TERM...SO WILL FAVOR THE 12Z WW3 AS IT
REFLECTS THE TRENDS OF THE PREFERRED GFS SOLN. HOWEVER...WL TIME
SHIFT SEAS A LTL FASTER MON TO REMAIN CONSISTENT WITH THE
PREVIOUSLY MENTIONED WIND TIME SHIFT.

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

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER CLARK/KELLS. OCEAN PREDICTION CENTER.



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