

845 

AGNT40 KWNM 070127

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN 

NWS OCEAN PREDICTION CENTER WASHINGTON DC

930 PM EDT SAT 6 AUG 2016 



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

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



AT 00Z A SHIP LOCATED ABOUT 150 NM NE OF CAPE HATTERAS ACROSS 

THE GULF STREAM REPORTED 25 KT. DIAMOND SHOALS BUOY 41025 ALSO 

HAD 23 KT REPORT AT 00Z. PREVIOUS GRIDS WHICH WERE BASED ON THE 

12Z GFS LOOK INITIALLY REPRESENTATIVE THIS EVENING. LATEST 

MODELS ARE IN GOOD AGREEMENT ACROSS THE NRN NT2 AND NT1 WATERS 

FOR THE NEXT SEVERAL DAYS. HOWEVER MODEL DISPARITY EXISTS WITH 

POTENTIAL SURFACE LOW DEVELOPMENT S OF THE NT2 WATERS THIS WEEK. 

AFTER MIDDAY NHC/WPC MEDIUM RANGE COORDINATION...WPC HAS 

INCLUDED A WEAK SLOW MOVING LOW OFF THE SE US COAST IN ITS 

MEDIUM RANGE GUIDANCE AT DAYS 4 THROUGH 7...WHICH LOOKS FAIRLY 

CLOSE TO LAST NIGHTS ECMWF. 12Z UKMET WAS SIGNIFICANTLY STRONGER 

THAN ECMWF FOR TWO CONSECUTIVE RUNS NOW. BEGINNING MON WILL BE 

FAVORING THE 00Z ECMWF WINDS TO ACCOUNT FOR THIS DEVELOPMENT.    



THE ABOVE MENTIONED SHIP ALSO REPORTED 16 FT AT 00Z WHICH WAS 

LIKELY DOUBLED. ACROSS THE W ATLC BOTH THE 12Z/18Z WAVEWATCH III 

AND 12Z ECMWF WAM ARE WELL INITIALIZED WITH WAVE HEIGHTS THIS 

EVENING.  



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

...PREVIOUS DISCUSSION...



SUMMARY...12Z NCEP SFC ANALYSIS SHOWS A WARM FRONT ARCING 

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 THIS MORNING SHOW WINDS OF 20 TO 25 

KT IN SW FLOW OVER THE CENTRAL AND SRN NT2 WTRS AND WINDS TO 20 

KT IN SW FLOW IN THE GULF OF MAINE...BUT OTHERWISE INDICATE 

WINDS OF 15 KT OR LESS OVER THE OFSHR WTRS. LIGHTNING DENSITY 

PRODUCT DATA AT 1840Z SHOW SCATTERED SHOWERS AND TSTMS OVER THE 

CENTRAL AND SRN NT2 WTRS. 



MAIN WEATHER FEATURES...A COLD FRONT WILL 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...THEN MOVE OFFSHORE THU AND THU NITE. A WEAK 

LOW COULD MOVE N THEN NW OVER THE SRN NT2 WTRS WED THRU THU. 



MODELS...THE 12Z MED RNG MDLS ARE IN VERY GUD OVERALL AGREEMNT 

FOR TONITE THRU TUE...SO THE REPRESENTATIVE 12Z GFS 10M SOLN 

WILL BE USED FOR THE WIND GRIDS OVER THIS TIMEFRAME. DURING THE 

TUE NITE THRU THU NITE PERIOD THE 12Z ECMWF/UKMET LIFT A LOW N 

INTO THE NT2 WTRS...ALTHO THE 12Z UKMET BECOMES MUCH STRONGER 

WITH THE LOW BY THU NITE. HOWEVER THE 12Z GEM/GFS DO NOT CARRY 

THE LOW COMING UP FROM THE S FOR TUE NITE THRU THU NITE...SO FOR 

NOW WILL NOT BE MENTIONING THIS LOW IN THE OFSHR WTRS FCST 

BECAUSE IT IS NEAR THE END OF THE FCST PERIOD AND THE OVERALL 

MDL AGREEMNT IS POOR ATTM. WILL USE THE 12Z ECMWF FOR TUE NITE 

THRU THU NITE SINCE IT APPEARS TO BE THE BEST MEDIAN MDL SOLN 

ATTM. 



SEAS...THE 12Z WNA WAVEWATCH III MDL AND THE 12Z ECMWF WAM BOTH 

INITIALIZED WELL OVER THE OFSHR WTRS. THE MDLS ARE IN VRY GUD 

AGREEMNT FOR TONITE THRU TUE...SO WILL JUST USE THE 12Z WNA 

WAVEWATCH III MDL FOR THIS TIMEFRAME. WILL BE USING A 25/75 

BLEND OF THE 12Z WNA WAVEWATCH III/ECMWF WAM FOR TUE NITE THRU 

THU NITE...DUE TO THE POSSIBILITY THAT THE GFS DRIVEN 12Z WNA 

WAVEWATCH III IS UNDER FCSTG THE WAVE HTS IN THE SRN NT2 WTRS 

FOR THAT PERIOD. 



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



.WARNINGS...PRELIMINARY. 



.NT1 NEW ENGLAND WATERS... 

     NONE. 



.NT2 MID ATLC WATERS... 

     NONE. 



$$ 



.FORECASTER CLARK/SCOVIL. OCEAN PREDICTION CENTER.

