165  
AGNT40 KWNM 221232  
MIMATN  
 
MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN  
NWS OCEAN PREDICTION CENTER WASHINGTON DC  
832 AM EDT FRI JUN 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 06Z SURFACE ANALYSIS SHOWS A COLD FRONT  
EXTENDING E TO W ACROSS THE NORTHERN GEORGES BANK WATERS INTO THE  
CAPE COD REGION. THE ANALYSIS ALSO SHOWS A 1009 MB LOW CENTERED  
OVER ZONE 910 IN THE NE PART OF THE NT2 AREA, WITH AN ASSOCIATED  
STATIONARY FRONT EXTENDING ROUGHLY W FROM THE LOW INTO THE CAPE  
HENRY REGION. OTHERWISE, THE SURFACE ANALYSIS SHOWS HIGH PRESSURE  
RIDGING IN THE OFFSHORE WATERS N OF THE COLD FRONT AND SE OF THE  
STATIONARY FRONT. LATEST AVAILABLE ASCAT HI-RES AND ASCAT PASSES  
FROM LAST NIGHT SHOW 15 TO 20 KT WINDS IN SW FLOW OVER THE  
SOUTHERN NT2 WATERS AND ALSO NEAR THE LOW IN THE NE NT2 WATERS.  
ELSEWHERE ACROSS THE OFFSHORE WATERS, ASCAT INDICATES 5 TO 15 KT  
WINDS. LIGHTNING DENSITY PRODUCT DATA AT 11Z SHOWS SCATTERED  
SHOWERS AND TSTMS S OF THE STATIONARY FRONT OVER THE CENTRAL AND  
SOUTHERN NT2 WATERS OFF THE NORTH CAROLINA COAST.  
 
MODELS/FORECAST...THE 00Z MODELS ARE IN VERY GOOD OVERALL  
AGREEMENT IN THE OFFSHORE WATERS FOR TODAY THROUGH SUN NIGHT, SO  
A REPRESENTATIVE 50/50 BLEND OF THE 12Z GFS 10M/00Z HI-RES WARW  
WILL BE USED FOR THE WIND GRIDS THROUGH SUN NIGHT TO MAINTAIN  
FORECAST CONTINUITY. THE 00Z ECMWF LOOKS LIKE A SIGNIFICANTLY  
FAST OUTLYER REGARDING A DEVELOPING LOW PASSING E OF THE  
OFFSHORE WATERS MON THROUGH TUE NIGHT, SO THE 00Z GFS 10M  
SOLUTION WILL BE USED FOR THE WIND GRIDS FOR MON THROUGH THE REST  
OF THE FORECAST PERIOD. WILL CONTINUE TO MENTION WINDS GUSTING  
TO 35 KT IN AND NEAR TSTMS ACROSS THE CENTRAL AND SOUTHERN NT2  
WATERS OFF THE NORTH CAROLINA COAST FOR TODAY, BUT BASED ON THE  
MODEL CONSENSUS, SUSTAINED WINDS OF 35 KT OR GREATER ARE NOT  
EXPECTED OVER THE OFFSHORE WATERS DURING THE FORECAST PERIOD.  
 
SEAS...THE 00Z WNA WAVEWATCH AND 00Z ECMWF WAM BOTH INITIALIZED  
WELL OVER THE OFFSHORE WATERS VERSUS RECENT BUOY OBSERVATIONS AND  
ALTIMETER DATA. SEAS IN THE OFFSHORE WATERS ARE CURRENTLY 5 FT OR  
LESS. A 50/50 BLEND OF THE 12Z/00Z WAVEWATCH WILL BE USED FOR THE  
SEA HEIGHT GRIDS FOR TODAY THROUGH SUN NIGHT TO MATCH UP WITH THE  
WIND GRIDS, THEN WILL GO EXCLUSIVELY WITH THE 00Z WAVEWATCH FOR  
MON THROUGH THE REST OF THE FORECAST PERIOD, IN ORDER TO BE  
CONSISTENT WITH THE PREFERRED 00Z GFS WIND GRIDS.  
 
EXTRATROPICAL STORM SURGE GUIDANCE...N/A.  
 
-----------------------------------------------------------------  
PREVIOUS DISCUSSION...  
 
OVER THE SHORT TERM, TODAY THROUGH THE WEEKEND INTO EARLY  
MONDAY, THE 00Z GLOBAL MODELS REMAIN IN VERY GOOD AGREEMENT AND  
QUITE CONSISTENT AS WELL. FOR THE EARLY MORNING PACKAGE WE WILL  
POPULATE GRIDS WITH A 50/50 BLEND OF THE PREVIOUS GRIDS AND 00Z  
HIGH RESOLUTION WARW WIND GUIDANCE FOR TODAY THROUGH SAT. THIS  
WILL RESULT IN LITTLE CHANGE FROM THE PAST FEW OPC FORECASTS  
THROUGH SAT. THE EARLY MORNING ASCAT OVERPASS INDICATED WINDS  
OVER THE OFFSHORE WATERS OF GENERALLY 20 KT OR LESS, WITH A FEW  
GALE FORCE WIND BARBS IN THE VICINITY OF THUNDERSTORMS MAINLY  
EAST AND SOUTHEAST OF CAPE HATTERAS. THE LATEST GOES-IR SATELLITE  
IMAGERY, RADAR DATA, AND LIGHTNING STRIKE DATA SHOWS THE HEAVIER  
THUNDERSTORMS OCCURRING NEAR AND OFF THE NORTH CAROLINA COAST  
EARLY THIS MORNING. WE WILL MENTION WINDS OF GALE FORCE OR HIGHER  
IN THESE ZONES WHERE THE BEST CHANCE FOR HEAVIER THUNDERSTORMS  
ARE EXPECTED FOR TODAY. OTHERWISE, WE STILL EXPECT HIGH PRESSURE  
TO BUILD OVER THE NEW ENGLAND WATERS TODAY AS A FRONT REMAINS  
NEARLY STATIONARY OFF THE DELMARVA AND NORTH CAROLINA COAST. AS  
THE HIGH MOVES OFF TO THE EAST OF THE WATERS TONIGHT INTO SAT THE  
FRONT WILL LIFT N AS A WARM FRONT. THE BEST CHANCE FOR HEAVIER  
THUNDERSTORMS WILL REMAIN NEAR THE FRONT INTO TOMORROW.  
 
OVER THE MEDIUM RANGE, SAT NIGHT THROUGH EARLY MON, THE 00Z  
GUIDANCE REMAINS IN GOOD AGREEMENT. WE WILL POPULATE GRIDS WITH  
A 50 PERCENT PREVIOUS GRIDS, 50 PERCENT 00Z 10 METER GFS WIND  
BLEND AS A RESULT DURING THIS TIME FRAME. A WARM FRONT WILL LIFT  
N OVER NEW ENGLAND WATERS SAT NIGHT, WITH LOW PRESSURE CROSSING  
THE GULF OF MAINE SUN WITH A TRAILING COLD FRONT PASSING SE OVER  
THE REGION DURING SUN AND SUN NIGHT WITH A SECOND LOW PASSING E  
OVER NORTHERN NEW ENGLAND WATERS SUN NIGHT. FOR MON INTO TUE  
NIGHT WE WILL POPULATE GRIDS WITH THE 00Z GFS 10 METER WINDS.  
THE 00Z GFS APPEARS TO BE IN GOOD AGREEMENT WITH THE 00Z UKMET,  
CANADIAN GEM AND NAVGEM, WHILE THE 00Z ECMWF APPEARS TO BE A  
SLIGHTLY FASTER OUTLIER REGARDING LOW PRESSURE MOVING EAST AWAY  
FROM THE AREA MON, FOLLOWED BY HIGH PRESSURE BUILDING SE INTO  
THE WATERS MON NIGHT INTO TUE NIGHT AS THE FRONT PUSHES JUST S  
OF THE OFFSHORE WATERS. CONFIDENCE LEVELS ARE SLIGHTLY ABOVE  
AVERAGE OVER THE REGION FOR THE NEXT 5 DAYS.  
 
SEAS: THE PREVIOUS WAVE HEIGHT GRIDS AND THE 00Z WAVEWATCH  
AND 00Z ECMWF WAM HAVE ALL INITIALIZED QUITE WELL OVER THE  
OFFSHORE WATERS EARLY THIS MORNING. SEA HEIGHTS RANGE FROM 6 FEET  
EAST AND SOUTHEAST OF CAPE HATTERAS TO 2 FEET OR SO OFF THE NEW  
ENGLAND COAST ACCORDING TO THE 06Z RA1 OPC SEA STATE ANALYSIS.  
IN ORDER TO MATCH THE WIND FORECAST AS DESCRIBED ABOVE, WE WILL  
USE A 50/50 BLEND OF THE PREVIOUS GRIDS AND 00Z WAVEWATCH FOR  
TODAY INTO EARLY MON, AND THEN STAY CLOSE TO THE 00Z WAVEWATCH  
FOR MON AND BEYOND. WE WILL MAKE A FEW MANUAL ADJUSTMENTS OVER  
THE FAR WESTERN AND SOUTHERN PORTIONS OF THE OFFSHORE WATERS IN  
DEFERENCE TO NEARBY COASTAL WFO AND TAFB GRIDS AND FORECAST  
DURING THE NEXT FEW DAYS.  
 
EXTRATROPICAL STORM SURGE GUIDANCE...N/A.  
   
WARNINGS
 
PRELIMINARY.  
   
NT1 NEW ENGLAND WATERS
 
 
NONE.  
   
NT2 MID-ATLANTIC WATERS
 
 
NONE.  
 

 
 
.FORECASTER SCOVIL/MILLS. OCEAN PREDICTION CENTER.  
 
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