

442 

AGNT40 KWNM 261320

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN 

NWS OCEAN PREDICTION CENTER WASHINGTON DC

920 AM EDT TUE 26 JUL 2016 



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

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



A 09Z RAPIDSCAT OVERPASS RETURNED W TO SW WINDS TO 25 KT ACROSS 

THE GULF STREAM THROUGH OUTER ZONES ANZ910 ANZ920 AND ANZ925. 

ALSO THERE WERE LIMITED 25 KT RETRIEVALS ACROSS INNER WATERS 

FROM HUDSON CANYON TO CAPE CHARLES LIGHT. OPC WIND GRIDS WHICH 

WERE BASED ON THE 00Z GFS WERE QUITE CONSISTENT WITH RAPIDSCAT. 

OVERNIGHT MODELS CONTINUED TO BE IN GOOD AGREEMENT ACROSS THE W 

ATLC FOR THE NEXT FEW DAYS. ALTHOUGH SLIGHLY LESS PROGRESSIVE 

THAN ITS PREVIOUS 00Z RUN...THE 06Z GFS WAS STILL ABOUT 12 HOURS 

OR SO FASTER THAN THE 00Z ECMWF/UKMET WITH THE DEVELOPING LOW 

MOVING OFF THE NRN MID ATLC COAST LATE FRI NIGHT AND SAT. 

PREVIOUS OPC WIND GRIDS LOOK REASONABLE THROUGH THE FORECAST 

PERIOD AND WILL NOT BE MAKING SIGNIFICANT ADJUSTMENTS THIS 

MORNING. THE 00Z/06Z WAVEWATCH III AND 00Z ECMWF WAM ARE WELL 

INITIALIZED WITH THE W ATLC WAVE HEIGHTS THIS MORNING.



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

PREVIOUS DISCUSSION...



CRNT LGTNG DENSITY PROD INDC TSTMS ACRS NE NT2 NEAR N WALL OF 

GULF STREAM IN W TO SW FLOW...AND ALSO ALONG A LOW PRES TROF 

NEAR THE MID ATLC COAST. THE 00Z GFS/ECMWF INDC A MDT AMT OF 

INSTABILITY OVR NT2 WITH THE PREDOMINANTLY SW FLOW INJECTING 

HEAT/MOISTURE INTO THE PBL. ALSO...THE MDLS INDC A PAIR OF SFC 

BNDRYS OVER THE AREA IN THE SHORT RANGE...TO ACT AS A FOCUS FOR 

CONVECTION...OVR NRN NT2. THE PREV FCST CARRIED SCTRD TSTMS AND 

SHOWERS IN NT2...SO PLANNING ON MAINTAINING MENTION IN THE NEXT 

PKG. 



OTRW...THE 00Z MDLS ALL INDC THE AFOREMENTIONED SFC TROF WL MOVE 

INTO THE AREA EARLY TDA...FLWD BY A FRNTL BNDRY CRNTLY JUST SE 

OF THE GREAT LAKES REGION...LATER TDA INTO TNGT. 0235Z ASCAT 

WIND RETRIEVALS AND CRNT SFC RPRTS INDC WINDS CRNTLY UP TO 20 KT 

IN THE SW FLOW AHD OF THE SFC TROF...AND 0235Z RSCAT WINDS 

EXTEND A LTL FURTHER E OVER THE GULF STREAM AND INDC 25 KT. THE 

00Z GFS WNDS ARE INIT OK WHEN COMPARED WITH THE CRNT DATA...AND 

INDC THAT THE WINDS WL NOT INCRS ANY FURTHER THAN 25 KT AHEAD OF 

THE TWO BNDRYS. THE 00Z GFS AGREES FAIRLY WELL WITH THE 00Z 

ECMWF/UKMET/NAM/GEM MDL RUNS WITH THE TMG OF THE BNDRY...BUT IS 

SLGTLY STGR THAN THE ECMWF/UKMET...AND A LTL WKR THAN THE 00Z 

NAM/GEM. ATTM THE GFS SEEMS TO BE ABT THE BEST CMPRMS SOLN IN 

THE SHORT RANGE...AND SEEMS MOST RSNBL...SO PLANNING ON FAVORING 

IT INTO THU NGT WHICH KEEPS FCST IN LINE WITH PREV ONE. 



THE BIGGEST FCST PROBLEM IS IN THE EXTENDED PD...AS THE 00Z GFS 

IS A FAST OUTLIER WITH THE NEXT SYS ON FRI INTO SAT. THE GFS HAD 

SLOWED SLIGHTLY TWD THE OVERALL MDL CONSNESUS WITH THE 18Z 

RUN...BUT HAS TRENDED FASTER AND AWAY FM IT WITH THE 00Z RUN. IN 

ADDITION...THE 00Z UKMET/GEM HAVE TRENDED TWD THE CONSISTENT 

ECMWF SOLN...WHICH IS ALSO SUPPORTED BY THE 00Z GEFS/ECWMF/NAEFS 

MEAN SOLNS. AS A RESULT...PLANNING ON FAVORING THE 00Z ECMWF 

SOLN FROM FRI 06Z ONWARD...THO WL BOOST WINDS INVOF THE GULF 

STREAM WHERE THE ECMWF WINDS SEEMS A BIT LOW. 



.SEAS...BOTH THE 00Z WAVEWATCH III AND ECMWF WAM MDLS HV BOTH 

INITIALIZED THE CURRENT W ATLC WAVE HEIGHTS VERY WELL...WITH WV 

HTS CRNTLY 6 FT OR LESS IN THE W ATLC. THE MDLS ARE IN GOOD 

AGREEMENT INTO FRI...SO PLANNING ON USING 00Z WW3 UNTIL THEN. WL 

THEN SWITCH TO 00Z ECMWF WAVE SOLN BY 06Z FRI...TO REFLECT 

PREFERRED WX MDL TRENDS. ALSO...WW3 BUILDS SEAS FASTER THAN THE 

ECMWF WAM...AS A RESULT OF STGR WINDS WITH THE FASTER LOW...SO 

PREFER TO STAY AWAY FM IT ATTM. 



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



.WARNINGS...PRELIMINARY. 



.NT1 NEW ENGLAND WATERS... 

     NONE. 



.NT2 MID ATLC WATERS... 

     NONE. 



$$ 



.FORECASTER CLARK/KELLS. OCEAN PREDICTION CENTER.

