

130 

AGNT40 KWNM 260057

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

857 PM EDT MON JUL 25 2016



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

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



LGTNG DENSITY PROD INDC STRONG TSTMS FROM EARLIER OVR NRN NT2 NEAR

N WALL OF GULF STREAM HAVE WEAKENED A BIT...AND GOES IR IMGRY

INDC CRNTLY OVR ZONE ANZ910 IN NE NT2. THE IMAGERY AND LGTNG DATA

INDC ANTHR ROUND OF TSTMS MOVG OFF THE MID ATLC COAST NEAR LONG

ISLAND...IN THE CONVERGENCE AHEAD OF A SFC TROF. THE PREV FCST

LOOKS IN LINE WITH THE WX GRIDS...SO NOT PLANNING ON MAKING ANY

CHAGES TO THEM.



OTRW...THE 12Z/18Z MDLS ALL INDC THE AFOREMENTIONED SFC TROF WL

MOVE INTO THE AREA TNGT...FLWD BY A FRNTL BNDRY CRNTLY ACRS THE

GREAT LAKES REGION...LATER TNGT INTO TUE NGT. THE CRNT SFC RPRTS

INDC WINDS CRNTLY UP TO 20 KT IN THE SW FLOW AHD OF THE FIRST

BNDRY...AND THE 12Z/18Z GFS 10M WNDS ARE INIT OK WHEN COMPARED

WITH THE DATA. THE GFS AGREES FAIRLY WELL WITH THE LTST

ECMWF/UKMET/NAM/GEM MDL RUNS WITH THE TMG OF THE BNDRY...AND INDC

THE WINDS WL INCRS TO 25 KT AS THE FRONT MOVES INTO THE

AREA...MAINLY OVER THE UNSTABLE ENVIRONMENT OVER THE GULF STREAM.

THE PREV FCST WENT WITH THE 12Z GFS IN THE FCST OVER THE SHORT

RANGE...AND ATTM SEE NO REASON TO DIVERT FROM IT AS IT IS

SUPPORTED BY OTHER GLOBAL/REGIONAL SOLNS.



THE BIGGEST FCST PROBLEM IS IN THE EXTENDED PD...AS THE GFS CONT

TO STAY A FAST OUTLIER WITH THE NEXT SYS ON FRI INTO SAT. THE 12Z

ECMWF IS STILL ABOUT THE BEST COMPROMISE SOLN WITH THE SPEED OF

THE SYS...BUT IS SLIGHTLY WKR THAN THE GFS/GEM SOLNS. ALSO GFS

TRENDED A LTL SLOWER IN THE 18Z RUN...IT IS STILL A LTL TOO FAST.

AS A RESULT...PLANNING ON STAYING WITH PREV LINE OF THINKING...AND

USING THE 12Z ECWMF WHILE BOOSTING THE WINDS. OTRW NOT PLANNING ON

MKG ANY SIG CHANGES FOR THE REMAINDER OF THE UPDATE PKG.



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

PREVIOUS DISCUSSION... 



A 1430Z METOP-B ASCAT OVERPASS RETURNED 25 TO 30 KT WINDS INVOF 

38.5N 72.5W ASSOCIATED WITH AREA OF STRONG CONVECTION LIKELY A 

SUPERCELL WHICH HAS SINCE MOVED TO NEAR 37.5N 70.5W. LATEST 

LIGHTNING DENSITY IS INDICATING CONVECTION HAS BECOME BETTER 

ORGANIZED AS IT PASSED ACROSS THE N WALL OF THE GULF STREAM LAST 

HOUR. SHIP REPORTED 40 KT NEAR THIS CONVECTION AT 18Z. THE 12Z 

MODELS ARE IN GOOD AGREEMENT ACROSS THE EASTERN SEABOARD FOR THE 

NEXT COUPLE DAYS...AND SHARE SIMILAR TIMING WITH A WEAK COLD 

FRONT APPROACHING FROM THE NW TODAY...MOVING SE ACROSS THE NT1 

WATERS TONIGHT/TUE...AND NRN NT2 WATERS TUE NIGHT. 12Z GFS 10M 

WINDS ARE WELL SUPPORTED BY OTHER GUIDANCE WITH WINDS TO 20 OR 

25 KT JUST S OF THIS FRONT. FRONT SHOULD THEN STALL AND WEAKEN 

ACROSS THE NT2 WATERS AS SERIES OF WEAK LOWS PASS E ALONG FRONT 

WED INTO THU.    



BY THU NIGHT/FRI 12Z GLOBAL MODELS GENERALLY AGREE THAT ANOTHER 

WEAK COLD FRONT WILL MOVE OFF THE NEW ENGLAND COAST. THE 12Z GFS 

THEN BECOMES A PROGRESSIVE OUTLIER WITH A DEVELOPING SURFACE LOW 

LATE FRI/SAT. 12Z GEFS ALSO SUGGESTING THAT IT IS TOO FAR S WITH 

THE LOW TRACK. 12Z ECMWF WAS CONSISTENT WITH ITS PREVIOUS FEW 

RUNS IN MOVING LOW THROUGH NT1 WATERS SAT INTO SAT NIGHT. 

HOWEVER VERSUS ITS 00Z RUN THE 12Z ECMWF WAS A BIT 

WEAKER...BACKING OFF FROM THE 30 KT WINDS SHOWN IN THE 00Z RUN. 

12Z UKMET IS SLOWER THAN ECMWF BUT SUPPORTS THE MORE NRN 

SOLUTION. AS A COMPROMISE FOR STRENGTH OF WINDS WILL USE A 50/50 

BLEND OF THE PAST TWO RUNS OF THE ECMWF FRI THROUGH THE 

WEEKEND...WHICH WILL ALSO BE VERY CLOSE TO LATEST WPC MEDIUM 

RANGE GUIDANCE. ADDED 10 PERCENT TO THESE BLENDED TO GET SLIGHLY 

MORE EXPANSIVE AREAS OF 25 KT WINDS ASSOCIATED WITH THE SURFACE 

LOW AND SE OF ITS COLD FRONT SAT/SAT NIGHT.   



.SEAS...OVERALL THE 12Z WAVEWATCH III AND 12Z ECMWF WAM MDLS HV 

BOTH INITIALIZED THE CURRENT W ATLC WAVE HEIGHTS VERY WELL...AND 

ARE IN GOOD AGREEMENT AT LEAST INTO FRI. WITH THE 12Z GFS BEING 

FAVORED...PLAN ON POPULATING WAVE HEIGHT GRIDS WITH ALL 12Z 

WAVEWATCH III FOR TODAY THRU THU NIGHT. THEN WITH PREFERENCE FOR 

ECMWF BLEND POPULATED WITH 50/50 BLEND OF 00Z AND 12Z ECMWF WAM  

FRI THROUGH THE WEEEKEND. 



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





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER KELLS/CLARK. OCEAN PREDICTION CENTER.

