

991 

AGNT40 KWNM 221414

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

1014 AM EDT MON AUG 22 2016



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

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



THE LATEST SAT IMG INDC A FRONTAL BOUNDARY ACROSS THE ERN

PORTIONS OF THE NRN AND AND CENTRAL WATERS WITH HEAVIER TSTMS OVER

THE CENTRAL REGION. ALL THE OBSERVATIONS INCLUDING AN EARLIER

ASCAT PASS ABOUT 0138Z INDC NW TO W WINDS OVER THE CENTRAL AND SRN

WATERS BUT S TO SW WINDS AHEAD OF THE FRONT OVER THE NRN AND ERN

PORTIONS OF THE CENTRAL WATERS. MAX NW WINDS TO 25 KT ARE BEHIND

THE FRONT BUT WINDS ARE EVEN HIGHER IN TSTMS. AT 12Z THE NCEP MAP

HAS LOW PRES 1007 MB NEAR THE MAINE WATERS WITH ITS COLD FRONT

EXTENDING S. BROAD INLAND HIGH PRES HAS ITS RIDGE INTO FAR WRN

PORTIONS OF THE SRN WATERS. THE PRES GRADIENT IS FAIRLY RELAXED.

THE OBSERVED SEAS ARE CURRENTLY LESS THAN 6 FT ACROSS THE REGION.

THE NWW3 MULTI GRID WABVE MODEL FITS VERY WELL WITH THE OBSERVED

SEAS PATERN AND MATCHES VERY WELL THE PEAK VALUES. NWW3 IS ALSO

VERY CLOSE TO THE ECMWFWAVE MODEL. BOTH MODELS ARE IN GOOD

AGREEMENT IN THE SHORT TERM AND SO FOR THIS UPDATE WILL CONTINUE

WITH WNA.



A WEAK UPPERLEVEL RIDGE WITH LITTLE ENERGY COVERS MOST OF THE

FORECAST WATERS. THE FAR NW PORTIONS HAS SOME ENRGY THAT IS PART

OF THE ENERGY EMBEDDED IN THE UPPERLEVEL CUT-OFF LOW OVER CANADA

THAT EXTENDS A TROF SE. THE MODELS INDC THAT THESE ENERGY WILL

QUICKLY MOVE E AND THAT WILL RESULT IN THE SFC LOW PRES OVER MAINE

TO MOVE E WITH IT. BEHIND THE TROF IS UPPERLEVEL RIDGE WITH LITTLE

ENERGY THAT WILL EXTEND FROM HIGH PRES OVER THE SRN STATES. THE

MODELS INDC THAT THE HIGH PRES WILL REMAIN TO THE W OF THE WATERS

THRU THE FORECAST PERIOD AND ITS ERN RIDGE EXTENSION WILL BLOCK

ENEGRY FROM THE N TO GET INTO THE WATERS. AN UPPER LEVEL ZONAL

FLOW ACROS THE REGION WILL ALLOW SYNOP SYSTEMS TO MOVE FAST ACROS

THE WATERS.



GFS/UKMETHR/ECMEFHR/NOGAPS/CMC/JMA HAVE INITIALIZED WELL WITH THE

OBSERVED PRES FIELDS. THE MODELS HAVE JUST MINOR DIFFERENCES WITH

THE OBSERVATIONS IN WIND SPEED AND DIRECTION AND SO WILL JUST

CONTINUE THIS UPDATE WITH GFS. IN THE SHORT TERM THE MODEL AGREE

WELL ON MOVING THE LOW NEAR MAINE NE AS A COLD FRONT OVER THE

WATERS MOVES E WITH THE SRN PORTION STALLING OVER THE FAR S. HIGH

PRES WILL MOVE E JUST BEHIND THE FRONT AND THAT WILL ALLOW WINDS

TO SHIFT TO N TO NE OVER MOST OF THE REGION EXCEPT NW TO N WINDS

OVER PARTS OF THE NRN WATERS. 



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

PREVIOUS DISCUSSION...



SHORT TERM...THE MAIN CONCERN OVR THE SHORT TERM PORTION OF THE

FCST WILL BE THE LOCALLY VERY GUSTY WINDS AND VERY ROUGH SEAS IN

OR NEAR ANY OF THE HEAVIER TSTMS CURRENTLY OVR PORTIONS OF THE NRN

AND CENTRAL NT2 OFF WTRS. THESE TSTMS ARE OCCURRING NR A COLD

FRONT WHICH IS CROSSING THE NT1 AND NW NT2 WTRS CURRENTLY. THE

ASCAT OVERPASSES FROM LAST EVE INDICATED WINDS NR 35 KTS IN AND

NEAR THE TSTMS AND THIS TYPE OF WIND GUST IS STILL POSSIBLE WITH

THESE STORMS AS THE CROSS THE WTRS TODAY. THE LATEST RADAR...

SATELLITE...LIGHTNING DENSITY IMAGERY INDICATES THE HEAVIER TSTMS

EXTENDING FROM JUST E OF CAPE HATTERAS E-NE OVR CENTRAL AND NRN

NT2 WTRS OR MAINLY OVR THE OFF ZONES OF ANZ920...ANZ925...FAR NW

ANZ930...AND THEN W OVR ANZ830. THE LATEST SREF TSTM GUIDANCE

INDICATES THE BEST CHANCE FOR HEAVY TSTMS FROM THESE ZONES AND

POINTS E AND S TODAY...NR THE COLD FRONT. THE FRONT IS FCST TO

STALL OVR THE FAR SRN NT2 WTRS TONITE...AND THEN SLOWLY WEAKEN

TUE AND TUE NITE AS HIGH PRES OVERSPREADS MOST OF THE REGION. THE

FRONT WILL THEN LKLY DISSIPATE WED AS THE HIGH PRES AREA

DOMINATES THE WTRS. FOR THE EARLY AM PACKAGE WE WILL STAY CLOSE

TO THE 00Z GFS 10M WINDS THROUGH WED...WHICH WILL RESULT IN ONLY

MINOR CHANGES FROM THE PREV FEW OPC FCSTS. OVERALL...THE 00Z

GLOBAL MDLS REMAIN IN EXCELLENT AGREEMENT OVR THE REGION THRU

WED.



LONG TERM...BY EARLY THU...POST-TROPICAL FIONA...WILL BE

APPROACHING A PSN NR 30N67W PER THE LATEST NHC ADVISORY...AND

THEN REACH NR 31N68W BY EARLY THU NITE AS IT DISSIPATES. THIS

LOCATION IS ROUGHLY 200 NM SW OF BERMUDA...OR 250 NM SE OF THE

OFF WTRS. FOR ADDITIONAL INFORMATION PLS SEE THE LATEST ADVISORY

FROM THE NATIONAL HURRICANE CENTER. THIS SYSTEM DOES NOT APPEAR

AS IF IT WILL HAVE A SIGNIFICANT IMPACT ON CONDITIONS OVR THE OFF

WTRS OVR THE LONG TERM PORTION OF THE FCST. FOR THE EARLY AM

PACKAGE...WE WILL CONTINUE TO USE THE 00Z GFS 10M WINDS OVR THE

LONG TERM...AS THE 00Z GLBL MDLS REMAIN IN VRY GOOD AGREEMENT OVR

THE WTRS RIGHT THRU FRI NITE. THE HIGH PRES AREA NOTED IN THE

SHORT TERM PART OF THE FCST WILL WEAKEN OVR THE WTRS THU INTO FRI

AS THE NEXT COLD FRONT APPROACHES FROM THE NW. THE FRONT WILL

PASS INTO NT1...AND POSSIBLY FAR NW NT2 WTRS OVERNITE FRI. WE

WILL REDUCE THE SW WINDS BY 5-10 PERCENT OVR SO OVR NRN NT1 WTRS

LATE THU INTO FRI AS THE GFS APPEARS TO BE OVER-FORECASTING THESE

WINDS SOMEWHAT BASED ON THE LATEST GFS WIND BIAS FOR THIS REGION.



.SEAS...BOTH THE 00Z WNA WAVE WATCH III AND 00Z ECMWF WAM WAVE

MDLS ARE VERY SIMILAR OVR THE WTRS THRU WED NITE. THEREFORE WE SEE

NO NEED TO DEVIATE MUCH FROM THE 00Z WW3 INTO WED NITE. FOR THU

INTO FRI NITE WE WILL USE A BLEND OF THE WW3 AND WAM MDLS AS THE

WW3 APPEARS TO BE A LITTLE TOO HIGH IN THE SW FLOW OVR NT1 WTRS

THU INTO FRI.



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





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER MUSONDA/MILLS. OCEAN PREDICTION CENTER.

