

970 

AGNT40 KWNM 061236

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

836 AM EDT SAT AUG 6 2016



.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT

.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.



UPDATE...06Z NCEP SFC ANALYSIS SHOWS A WARM FRONT EXTNDG ROUGHLY E

TO W ACROSS THE CENTRAL AND SRN NT2 WTRS...WITH A COLD FRONT

APPROACHING THE NEW ENGLAND STATES. LATEST AVAILABLE ASCAT AND

ASCAT HI-RES PASSES FROM LAST NITE SHOW WINDS TO 20 KT IN S TO SW

FLOW OVER THE GULF OF MAINE...BUT OTHERWISE INDICATE WINDS OF 15

KT OR LESS OVER THE OFSHR WTRS. LIGHTNING DENSITY PRODUCT DATA AT

1110Z SHOW SCATTERED SHOWERS AND TSTMS OVER THE CENTRAL NT2 AND

INNER ZONES OF THE SRN NT2 WTRS.



MAIN WEATHER FEATURES...A COLD FRONT WILL APPROACH THE COAST FROM

THE NW TODAY...MOVE OFFSHORE THIS EVNG AND TONITE...CONTINUE SE

OVER THE OFSHR WTRS SUN AND SUN NITE...THEN STALL AND WEAKEN

ACROSS THE SRN NT2 WTRS MON INTO TUE. ANOTHER COLD FRONT WILL

APPROACH THE COAST FROM THE NW LATE WED AND WED NITE. A WEAK LOW

COULD MOVE N INTO THE SRN NT2 WTRS WED AND WED NITE.



MODELS...THE MED RNG MDLS ARE IN VERY GUD OVERALL AGREEMNT FOR

TODAY THRU MON NITE...SO THE REPRESENTATIVE GFS 10M SOLN WILL BE

USED FOR THE WIND GRIDS OVER THIS TIMEFRAME. DURING THE TUE THRU

WED NITE PERIOD THE NAM/ECMWF/UKMET MDLS FORM A LOW OVER THE NRN

BAHAMAS AND BRING IT NORTHWARDS UP INTO THE SRN NT2 WTRS ON WED

AND WED NITE. THE GEM ALSO FORMS THIS LOW BUT IS MUCH SLOWER AND

STRONGER WITH IT THAN THE OTHER MDLS. FOR NOW WILL NOT BE NOTING

THIS LOW IN THE OFSHR WTRS FCST BECAUSE IT IS NEAR THE END OF THE

FCST PERIOD AND THE OVERALL MDL AGREEMNT IS NOT THAT GUD ATTM. AM

NOT PLANNING TO MAKE ANY SIGNIF CHANGES TO THE CURRENT FCST TREND.



SEAS...WNA WAVEWATCH III MDL AND ECMWF WAM BOTH INITIALIZED WELL

OVER THE OFSHR WTRS. THE MDLS ARE IN VRY GUD AGREEMNT FOR TODAY

THRU MON...SO WILL JUST USE THE WNA WAVEWATCH III MDL FOR THIS

TIMEFRAME. WILL BE USING A 25/75 BLEND OF WNA WAVEWATCH III/ECMWF

WAM FOR MON NITE THRU WED NITE...DUE TO THE PROBABILITY THAT THE

GFS DRIVEN WNA WAVEWATCH III MDL IS UNDER FCSTG THE WAVE HTS IN

THE SRN NT2 WTRS FOR THAT PERIOD.



EXTRATROPICAL STORM SURGE GUIDANCE...N/A.



-----------------------------------------------------------------

PREVIOUS DISCUSSION... 



AN 02Z METOP-A ASCAT OVERPASS CONFIRMED THE 20 TO 25 KT WINDS 

ACROSS THE WRN GULF OF MAINE. THE 00Z GFS/NAM/UKMET/ECMWF WERE 

ALL SLIGHTLY UNDERDONE OVER THE GULF OF MAINE. EVEN 03Z HRRR AND 

RAP WERE INITIALIZED WITH MAX WINDS OF 20 KT. HOWEVER GULF OF 

MAINE BUOYS SUGGESTING THAT WINDS HAVE DIMINISHED SOMEWHAT OVER 

THE PAST FEW HOURS. ACROSS THE NT2 WATERS 0120Z AND 0300Z ASCAT 

RETURNED A FEW AREAS OF SW WINDS TO 20 KT S OF HATTERAS CANYON 

WHICH IS MOSTLY CONSISTENT WITH LATEST GUIDANCE. THE 00Z MODELS 

CONTINUE TO BE IN WELL ABOVE AVERAGE AGREEMENT ACROSS THE W ATLC 

FOR THE NEXT SEVERAL DAYS. 00Z MODELS ALL INDICATE THAT SW WINDS 

WILL GRADUALLY INCREASE TODAY AND TONIGHT AS A COLD FRONT 

APPROACHES THE NEW ENGLAND AND NRN MID ATLC COASTS TODAY AND 

MOVES SE ACROSS THE WATERS TONIGHT AND SUN BEFORE STALLING NEAR 

CAPE HATTERAS SUN NIGHT. 00Z GUIDANCE LOOKS REASONABLE IN 

LIMITING THE 25 KT WINDS TO NT2 ZONES ACROSS THE GULF STREAM. 

THERE IS ALSO CONSISTENCY BETWEEN MODELS THAT A RAPIDLY MOVING 

SECONDARY COLD FRONT WILL PASS SE ACROSS THE NEW ENGLAND AND 

NERN MID ATLC WATERS SUN NIGHT. THE STATIONARY FRONT SHOULD WASH 

OUT TUE AS HIGH PRES BUILDS OFFSHORE FROM NEW ENGLAND LATE MON 

THROUGH TUE NIGHT. GIVEN MODEL AGREEMENT AM CHOOSING TO POPUALTE 

WIND GRIDS WITH THE 00Z GFS THROUGH MON.  



MODEL DISPARITY BECOMES APPARENT ACROSS THE SRN NT2 WATERS NEXT 

WEEK AS THE ECMWF/NAM AND NOT SURPRISINGLY THE CMC ARE 

DEVELOPING A SURFACE LOW NEAR THE NRN BAHAMAS MON AND AT LEAST 

IN THE CASE OF THE ECMWF AND NAM MOVING IT TOWARD THE NT2 WATERS 

MON NIGHT. THE 00Z ECMWF KEEPS IT QUASI STATIONARY ACROSS THE 

SRN OUTER NT2 WATERS FOR MOST OF THE WEEK. ALTHOUGH SLOWER THAN 

THE ECMWF TO MOVE THE LOW N INTO NT2 WATERS THE 00Z UKMET IS NOW 

ALSO INDICATING A LOW. GFS AND GEFS CONTINUE TO SHOW NO 

DEVELOPMENT. WITH NAM/UKMET TRENDING TOWARD ECMWF PLAN TO USE 

THE 00Z ECMWF AS BASIS FOR WIND GRIDS MON NIGHT THROUGH THE 

REMAINDER OF THE WEEK AS ELSWHERE ACROSS THE NRN NT2 AND NT1 

WATERS MODELS ARE IN GENERAL AGREEMENT AT THAT TIME.   



.SEAS...HAVE HAD A FEW 7 FT BUOY REPORTS ACROSS THE GULF OF 

MAINE WHICH ARE A COUPLE FT HIGHER THAN EITHER THE 00Z ECMWF WAM 

OR 00Z WAVEWATCH III. ADJUSTED GRIDS HIGHER OVER THE NEAR TERM 

ACROSS THE GULF OF MAINE. USED 00Z WW3 THROUGH MON THEN 

TRANSITIONED TO A 75/25 BLEND OF THE 00Z ECMWF WAM AND 00Z WW3 

MON NIGHT THROUGH THE END OF THE FORECAST PERIOD. 



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



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER SCOVIL/CLARK. OCEAN PREDICTION CENTER.

