

790 

AGNT40 KWNM 071329

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

929 AM EDT SUN AUG 7 2016



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

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



GOES VIS IMGRY INDC A FRONTL BNDRY ACRS THE NRN NT2 WTRS...AND THE

LGTNG DENSITY PROD INDC TSTMS ALONG THE FRONT...MAINLY IN THE

UNSTABLE ENVIRONMENT OVER THE GULF STREAM. PREV FCST GRIDS INDC

SHOWERS AND TSTMS IN NT2 ASSOC WITH THE FRONT AS IT MOVES SLOWLY 

S...SO ATTM PLANNING ON MAINTAINING MENTION IN THE UPDATE PKG.



THE 06Z GFS HAS NOT CHANGED MUCH FM THE PREV RUN...AND INDC THE

FRONT WL DRIFT S INTO TUE NGT WHILE SLOWLY WKNG. THE REST OF THE

00Z MDLS AGREE FAIRLY WITH THE GFS ON THE TMG/INTNSTY OF THE

FRONT...SO NOT PLANNING ON MAKING ANY SIG CHANGES IN THE SHORT

RANGE. CRNT SFC RPRTS INDC WINDS TO 20 KT IN THE SW FLOW AHD OF

THE FRONT...AND 0445 UTC RSCAT AND 0240 UTC ASCAT WIND RETRIEVALS

INDC WINDS IN THE 25 TO 30 KT RNG. HOWEVER...THE MDLS INDC THAT

THE HIGHER WINDS HAVE MOVED JUST E OF THE OFSHR WTRS...SO WL START

OUT WITH MAINLY 20 KT...WITH A FEW SML AREAS OF 25 KT ON THE ERN

EDGE OF C NT2.



THE 00Z/06Z MDLS INDC ANTHR FRONTAL BNDRY WL MOV SE INTO NT1 WED

NGT INTO THU...AND AGAIN INCRS THE WINDS IN THE SW FLOW BTWN IT

AND HIGH PRES TO THE SE. THE PREV FCST WENT UP 25 KT IN THE GULF

OF MAINE IN THE SW FLOW...AND NOT XPCTG MORE THAN THAT WITH THE

HIGHER STATIC STABILITY OVR THE SHELF WATERS...SO WL CONT AT THAT

MAX VALUE. THE 00Z HAD BEEN SLIGHTLY FASTER WITH THE TMG OF THIS

SECOND BNDRY...AND THE PREV FCST HAD PREFERRED THE SLOWER 00Z

ECMWF OVER THE GFS...AS IT HAD MORE SUPPORT FOR IT FROM THE REST

OF THE 00Z GUID. THE 06Z GFS TRENDED SLOWER...MORE LIKE THE

ECWMF...SO PLANNING ON STAYING WITH CONTINUTIY FOR THIS FEATURE AS

PREV FCST SEEMS RIGHT ON TRACK. OTRW NOT PLANNING ON MKG SIG

CHANGES IN THE UPDATE PKG.



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

PREVIOUS DISCUSSION... 



0150Z AND 0240Z ASCAT OVERPASSES CONFIRMED SW WINDS TO 25 KT 

EXTENDING FROM S OF CAPE HATTERAS E AND NE TO 74W WHICH WAS EDGE 

OF PASS. AT 06Z THE COLD FRONT EXTENDED FROM GEORGE BANK SW 

ACROSS THE NRN NT2 WATERS TO THE DELMARVA PENINSULA. ASCAT DATA 

INDICATE THAT THE 25 KT WINDS ARE LIMITED TO THE WARMER GULF 

STREAM WATERS THIS MORNING. THE 00Z MODELS ARE IN GOOD AGREEMENT 

THAT THE 25 KT WINDS NOTED ABOVE WILL GRADUALLY DIMINISH TODAY 

AND COLD FRONT CONTINUES TO PUSH SE ACROSS NT2 WATERS WHILE 

WEAKENING. THIS FRONT SHOULD STALL NEAR CAPE HATTERAS TONIGHT AS 

A SECONDARY COLD FRONT EMERGES OFF THE NEW ENGLAND COAST. HIGH 

PRES SHOULD THEN SLOWLY BUILD E ACROSS THE NT1 AND NRN NT2 

WATERS MON INTO WED. 00Z GFS LOOKS REPRESENTATIVE THROUGH MON 

NIGHT SO WILL POPULATE WITH ITS WINDS THROUGH THAT TIME. 



00Z MODELS CONTINUED TO HAVE DIFFICULTY WITH A POTENTIAL 

DEVELOPING SURFACE LOW APPROACHING THE SRN NT2 WATERS LATE 

TUE/WED. GFS HAS CONSISTENTLY SHOWN LITTLE OR NO DEVELOPMENT 

WHILE ECMWF HAS BEEN FAIRLY CONSISTENT ON ITS OWN IN MOVING A 

WEAK LOW INTO THE NT2 WATERS. THE 12Z/06 UKMET HAD BEEN A STRONG 

OUTLIER AND NOW THE 00Z UKMET HAS TOTALLY LOST THE FEATURE. AS A 

COMPROMISE...TO MAINTAIN CONTINUITY AND STAY CONSISTENT WITH WPC 

MEDIUM RANGE GUIDANCE WILL KEEP A WEAK LOW IN WIND GRIDS. USED 

THE 00Z ECMWF FOR WINDS TUE/TUE NIGHT THEN TRANSITIONED TO A 

50/50 BLEND OF THE PREVIOUS GRIDS WITH THE 00Z ECMWF WED THROUGH 

THU NIGHT. BUMPED UP THIS BLEND BY ABOUT 15 PERCENT TO GET WINDS 

ASSOCIATED WITH DEVELOPING LOW TO 20 KT THU/THU NIGHT. LATE IN 

THE FORECAST PERIOD ACROSS THE NT1 WATERS MODELS AGREE THAT 

ANOTHER COLD FRONT WILL APPROACH THE COAST. THE 00Z GFS APPEARS 

SOMEWHAT OVERDONE WITH THE OFFSHORE WINDS AHEAD OF THIS FRONT. 

THE ABOVE MENTIONED BLEND RESULTS IN WINDS TO 20 OR 25 KT THU 

AND THU NIGHT ACROSS THE NT1 WATERS.   



.SEAS...THE DIAMOND SHOALS BUOY 41025 HAD AN 8 FT REPORT AT 

06Z...WHICH WAS AT LEAST A COUPLE FT HIGHER THAN THE 00Z 

WAVEWATCH III OR 00Z ECMWF WAM. ELSEWHERE ACROSS THE W ATLC THIS 

GUIDANCE LOOKS WELL INITIALIZED THIS MORNING. WAVE MODEL 

PREFERENCE WAS CONSISTENT WITH PREFERENCES FOR WIND GUIDANCE. 

USED THE 00Z WW3 THROUGH MON NIGHT...FOLLOWED BY THE 00Z ECMWF 

WAM TUE/TUE NIGHT...AND THEN 50/50 BLEND OF PREVIOUS WAVE HEIGHT 

GRIDS AND 00Z ECMWF WAM WED THROUGH THU NIGHT. 



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





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER KELLS/CLARK. OCEAN PREDICTION CENTER.

