924  
AGNT40 KWNM 221938  
MIMATN  
 
MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN  
NWS OCEAN PREDICTION CENTER WASHINGTON DC  
338 PM EDT SUN APR 22 2018  
   
FORECAST DISCUSSION
 
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT  
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.  
 
CURRENT CONDITIONS...THE 12Z NCEP SURFACE ANALYSIS SHOWS A LOW  
PRESSURE TROUGH APPROACHING THE GULF OF MAINE FROM THE N, WITH A  
HIGH PRESSURE RIDGE OVER THE OFFSHORE WATERS.  
 
MODELS/FORECAST...A LOW PRESSURE TROUGH WILL PASS SE OVER THE  
NT1 AREA THIS EVENING AND TONIGHT. THE RIDGE WILL BUILD SE OVER  
THE OFFSHORE WATERS TONIGHT AND MON, THEN SHIFT E OVER THE NT1  
AND NORTHERN NT2 WATERS MON NIGHT THROUGH TUE NIGHT. LOW PRESSURE  
WILL MOVE E ACROSS THE GULF COAST STATES THROUGH MON, TRACK NE  
ALONG THE SE COAST MON NIGHT THROUGH TUE NIGHT, PASS N OVER THE  
MID ATLANTIC WATERS WED, MOVE NE AND INLAND OVER NEW ENGLAND WED  
NIGHT AND THU, THEN MOVE OFF TO THE NE THU NIGHT. INTERACTION  
BETWEEN THE LOW AND RIDGE WILL RESULT IN GALE FORCE E TO SE FLOW  
OVER THE OFFSHORE WATERS FOR THE MON NIGHT THROUGH WED TIMEFRAME.  
 
12Z MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT OVER THE OFFSHORE  
WATERS FOR TONIGHT THROUGH TUE NIGHT, SO THE REPRESENTATIVE 12Z  
GFS 10M/30M SOLUTION WITH THE STABILITY SMART TOOL WILL BE USED  
FOR THE WIND GRIDS THROUGH TUE NIGHT. THE 12Z GFS IS FASTER AND  
LESS INLAND THAN THE OTHER MODELS WITH THE LOW FOR WED THROUGH  
THU NIGHT, THEN THE 12Z GFS HAS A STRONG COASTAL LOW FOR FRI AND  
FRI NIGHT WHILE THE OTHER MODELS ARE SIGNIFICANTLY WEAKER AND  
SLOWERS. SO THE GFS LOOKS LIKE AN OUTLYER SOLUTION FOR WED  
THROUGH FRI NIGHT, AND WILL USE A BOOSTED VERSION OF THE 12Z  
ECMWF FOR THIS TIMEFRAME SINCE IT IS MUCH MORE REPRESENTATIVE.  
CONFIDENCE IN THE GALE WARNINGS THROUGH TUE NIGHT IS ABOVE  
AVERAGE, DUE TO GOOD MODEL AGREEMENT. CONFIDENCE IN THE GALE  
WARNINGS FOR WED ONWARDS IS AVERAGE AT BEST, BECAUSE OF SOME  
DIVERGENCE AMONG THE MODELS.  
 
SEAS...THE 12Z WNA WAVEWATCH AND 12Z ECMWF WAM BOTH INITIALIZED  
WELL OVER THE OFFSHORE WATERS. THE ECMWF WAM IS TRENDING  
SOMEWHAT HIGHER WITH THE SEAS FOR TONIGHT THROUGH THU, FOLLOWED  
BY THE WNA WAVEWATCH TRENDING HIGHER FOR FRI AND FRI NIGHT.  
WILL BE FAVORING A REPRESENTATIVE BLEND OF THE 12Z WNA  
WAVEWATCH/ECMWF WAM THROUGH THE ENTIRE FORECAST PERIOD, IN ORDER  
TO SMOOTH OUT THE MODEL DIFFERENCES.  
 
EXTRATROPICAL STORM SURGE GUIDANCE...LATEST RUN OF ESTOFS AND  
ETSS SHOWS A POSITIVE SURGE IN THE 1 TO 2 FT RANGE ALONG THE SE  
COAST FOR TONIGHT INTO TUE, EXPANDING ALONG THE MID ATLANTIC  
COAST FOR LATE TUE THROUGH WED, THEN EXPANDING UP INTO THE NEW  
ENGLAND WATERS FOR LATE WED AND WED NIGHT. THE SURGE GUIDANCE  
LOOKS REASONABLE GIVEN THAT ALL OF THE MEDIUM RANGE MODELS HAVE  
BEEN SHOWING STRENGTHENING E TO SE FLOW OVER THE OFFSHORE WATERS  
FOR TONIGHT INTO WED NIGHT.  
   
WARNINGS
 
PRELIMINARY.  
   
NT1 NEW ENGLAND WATERS
 
   
ANZ800...GULF OF MAINE
 
 
GALE POSSIBLE WEDNESDAY NIGHT.   
ANZ805...GEORGES BANK WEST OF 68W
 
 
GALE POSSIBLE WEDNESDAY NIGHT.   
ANZ900...GEORGES BANK EAST OF 68W
 
 
GALE POSSIBLE WEDNESDAY NIGHT.   
ANZ810...SOUTH OF NEW ENGLAND
 
 
GALE POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT.    
ANZ815...SOUTH OF LONG ISLAND
 
 
GALE POSSIBLE WEDNESDAY.  
   
NT2 MID-ATLANTIC WATERS
 
   
ANZ820...HUDSON CANYON TO BALTIMORE CANYON
 
 
GALE POSSIBLE WEDNESDAY.   
ANZ915...HUDSON CANYON TO THE GREAT SOUTH CHANNEL
 
 
GALE POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT.    
ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL
 
 
GALE POSSIBLE TUESDAY NIGHT INTO WEDNESDAY NIGHT.    
ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE
 
 
GALE POSSIBLE WEDNESDAY NIGHT.   
ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N
 
 
GALE POSSIBLE WEDNESDAY INTO WEDNESDAY NIGHT.    
ANZ825...INNER WATERS FROM BALTIMORE CANYON TO CAPE CHARLES LIGHT
 
 
GALE POSSIBLE TUESDAY NIGHT INTO WEDNESDAY.    
ANZ828
 
INNER WATERS FROM CAPE CHARLES LIGHT TO CURRITUCK BEACH LIGHT...  
GALE TUESDAY.  
GALE POSSIBLE TUESDAY NIGHT.   
ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON
 
 
GALE TUESDAY.  
GALE POSSIBLE TUESDAY NIGHT INTO WEDNESDAY.    
ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS
 
 
GALE MONDAY NIGHT INTO TUESDAY.  
GALE POSSIBLE TUESDAY NIGHT.   
ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR
 
 
GALE MONDAY NIGHT INTO TUESDAY.    
ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR
 
 
GALE MONDAY NIGHT INTO TUESDAY.  
GALE POSSIBLE TUESDAY NIGHT INTO WEDNESDAY.    
ANZ835...INNER WATERS FROM CAPE FEAR TO 31N
 
 
GALE MONDAY INTO TUESDAY.    
ANZ935...OUTER WATERS FROM CAPE FEAR TO 31N
 
 
GALE MONDAY NIGHT INTO TUESDAY.  
 

 
 
.FORECASTER SCOVIL. OCEAN PREDICTION CENTER.  
 
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