Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 020055
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
855 PM EDT SAT AUG 1 2015

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

THE CSTL/OFSHR WTRS ARE UNDER THE INFLUENCE OF A GNRLY WEAK
(PRIMARILY 10-20 KT) SSWLY GRADIENT AT THE MOMENT. HIGHEST SEAS
THRUT ARE GNRLY IN THE 7-9 FT RANGE...HIGHEST ACRS THE NE MOST NT2
WTRS...WHICH ARE BEING HANLDED BETTER BY THE 18Z WAVEWATCH III VS
THE 12Z ECMWF WAM MDL AT THE MOMENT.

OVER THE SHORT TERM...THE LATEST MDLS ARE IN GOOD AGRMT THAT A
WEAK COLD FRONT WL MOV OFSHR INTO THE NT1 AND FAR NW NT2 WTRS
TONITE...THEN DSIPT SUN. THEN AS A RIDGE SE OF THE OFSHR WTRS
STRENGTHENS SMWHT SUN NITE INTO MON NITE...AND ANOTHER INLAND
COLD FRONT APRCHS FM THE NW MON/MON NITE TO VARYING DEGREES THE
MDLS ALL FCST THE SSWLY GRADIENT TO STRENGTHEN THRUT. WITH THE 18Z
GFS RMNG CONSISTENT...FOR NOW WL CONT TO USE THE PREVLY POPULATED
12Z GFS 10M BL WIND SOLUTION FOR THIS GRADIENT WHICH IS ALSO SPRTD
BY THE 12Z ECMWF. SO AT MOST PLAN ON MAKING ONLY SM MINOR INSIG
SHORT TERM TWEAKS TO THE PREV OFSHR FCSTS.

IN THE LONG RANGE...WULD AGAIN FAVOR A BLENDED 18Z/12Z GFS AND 12Z
ECMWF SOLUTION FOR THE COLD FRONT TO MOV OFSHR TUE NITE WHL
WKNG...FLWD BY ANOTHER SCNDRY COLD FRONT PUSHING SE ACRS THE NT1
WTRS WED/WED NITE...THEN BCMG STNRY ACRS THE NRN NT2 WTRS THU/THU
NITE. AS ONE WULD EXPECT SINCE ITS DAY FIVE...THE LATEST GLOBAL
MDLS DIFFER ON THEIR FCST TRACKS/STRENGTHS OF ANY ASCD FRONTAL
WAVES TRACKING E ALONG THE FRONT THU/THU NITE. FOR NOW THE 12Z GFS
SOLUTION FOR THU/THU NITE...WHICH IS IN LINE WITH THE LATEST WPC
MEDIUM RANGE GUIDANCE...LOOKS REPRESENTATIVE. THEREFORE AGAIN PLAN
ON USING THE PREVLY POPULATED 12Z GFS 10M BL WINDS THRUT THE LONG
RANGE THRU THU NITE WITH AGAIN JUST SM MINOR ADDITIONAL EDITS
MAINLY IN DEFERENCE TO THE 18Z GFS/12Z ECMWF. SO ANTICIPATE MAKING
ONLY MINOR LONG RANGE CHNGS IN THE NEXT OFSHR FCST PACKAGE.



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

THE LTST GOES VIS/IR IMGRY AND THE LGTNG DENSITY PROD INDC A
FRNTL SYS OVR NT2 WITH SCTRD SHOWERS AND TSTMS ALNG THE
BNDRY...WITH A FRNTL WAVE E OF NE NT2...TO THE S OF NOVA SCOTIA. ASCAT
FM 15Z INDC A LRG AREA OF 30 KT JUST SE OF NRN NT2 WTRS ALNG THE
BNDRY...AND A SML AREA OF GALES IN SW FLOW OVR THE UNSTABLE ENVRMT
IN THE GLF STRM. CRNT SFC RPRTS INDC WNDS TO 20 KT OVR THE OFSHR
WTRS INVOF THE FRNT...AND 12Z GFS WNDS ARE INIT OK WHEN COMPARED
WITH THE DATA AND INDC ABT 25 KT CRNTLY OVR NT2 ALNG THE FRNT. THE
MDL WV IMGRY INDC A VRY WK VORT ALNG THE COAST NR SC...AND THE
12Z MDLS ALL INDC THE FRCG FM THE WK VORT WL DVLPG ANTHR LOW ALNG
THE FRONT...AND MOVE OFF TO THE NE QUICKLY TNGT INTO SUN. THE 12Z
ECMWF/GFS AGREE WELL ON THE FEATURE...AND THE GFS INDC WNDS WL
CONT AT 25 KT INTO SUN. THE ECMWF IS SLGTLY WKR...BUT WITH THE
MAJORITY OF SOLNS AGREEING ON THIS WK FEATURE...AND THE NRML LOW
BIAS ON THE ECWMF SUGGESTING A SLGTLY HIGHER MAX WND PSBL...WL
CONT 25 KT ALNG THE BNDRY INTO SUN.

THE GOES WV INDC ALSO AN UPR RDG OVR THE WRN AND C ATLC...AND A
TROF MOVG INTO THE GRT LKS RGN. THE MODIS RGB IMGRY RM 07Z INDC
WK H5 ENERGY ASSOC WITH THE UPR TROF...AND THE LTST NCEP SFC
ANALYS A WK SFC TROF ALNG THE NEW ENGLAND COAST. THE 12Z MDLS ALL
INDC THE WK FEATURE WL PASS THRU NT1 TNGT AND SUN...WITH ONLY
MINOR DIFFS ON THE TMG...SO PLANNING ON STAYING WITH 12Z GFS FOR THIS
SYS.

OTRW...PREV TMG ISSUES WITH THE NEXT ROUND OF SHRTWV ENERGY THRU
NT1 MON INTO WED HAS BEEN RESOLVED SOMEWHAT...WITH THE 12Z GFS H5
PTTN BCMG SLTLY MORE AMPLIFIED THAN THE 06Z RUN. AT THE SFC...THE
TMG OF THE ASSOC SFC FRNT IN THE GFS HAS TRENDED SLOWER FM PREV
RUNS...AND IS NOW IN BETTER AGRMT WITH THE 12Z ECWMF. THE 12Z GEM
AND TO A CERTAIN EXTENT THE 12Z UKMET STILL HAVG FEEDBACK
ISSUES...AND ARE OVRDVLPG LOWS THRU NT2...WITH THE GEM DVLPG A
PAIR OF STORM FRC LOWS ON BTWN MON AND TUE NGT. THE UKMET IS NOT
QUITE AS STG...BUT INDC GALES WITH THE LOW ON TUE NGT. FEELING THE
STGR SOLNS ARE A BIT TOO STG...ESP WITH THE 12Z ECMWF AND GFS FAR
WKR...AND THE GENL LOOK OF CNVCTV FEEDBACK IN THE GEM/UKMET
SOLNS...SO WL CONT TO DISCARD THOSE SOLNS FOR THE INTNSTY FCST.
HOWEVER...THE 12Z GFS/ECWMF ARE IN MUCH BETTER AGRMT INTO WED
NGT...UNTIL TMG DIFFS APPEAR AGAIN ON THU WITH THE NEXT SHRTWV
THRU NT1. THE 12Z ECMWF TRENDED FASTER WITH THIS SHRTWV AND ASSOC
SFC FEATURE...WHICH IS A LTL SURPRISING...SINCE THE UPR PTTN IS
STILL SOMEWHAT AMPLIFIED...AND WOULD LEAD ONE TO BLV THAT SLOWER
IS BETTER. THE 12Z GEM/UKMET ARE THE SLOWER...AND KEEP THE ENERGY
JUST INLD UNTIL LATE THU NGT. THE 12Z IS ABT THE BEST CMPRMS WITH
THE SPEED OF THIS FEATURE...SO ATTM PLANNING AT STAYING WITH THE
12Z GFS THRUT THE PD.

SEAS...THE 12Z WAVEWATCH III AND ECMWF WAM MDLS HV INITIALIZED
THE CURRENT SEAS FAIRLY WELL...THO A FT LOW JUST OF NT2 WITH THE
GALE OF THE WATERS...AS INDC BY 16Z ALTIMETER PASS WITH 16 FT INVOF
AREA OF GALES. OTRW...THE MDLS AGREE FAIRLY WELL INTO WED
NGT...THEN TMG DIFFS FM ASSOC WX MDLS CREATE DIFFS WITH THE WAVE
MDL SOLNS. ATTM PLANNING ON USING A 50/50 BLEND OF WAV MDLS AS A
CMPMS TO MINOR DIFFS BTWN SOLNS...THEN USE 12Z MWW3 IN WED NGT
ONWARD IN CONJUNCTION WITH PREFERRED GFS WX MDL SOLN.

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


.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER VUKITS/KELLS. OCEAN PREDICTION CENTER.


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