173
AGNT40 KWNM 281353
MIMATN
MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
953 AM EDT WED APR 28 2021
FORECAST DISCUSSION
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.
NO CHANGES ARE ANTICIPATED FOR THE MORNING UPDATE AS THE EXISTING
WIND GRIDS REPRESENTATIVE OF CURRENT CONDITIONS. THE 06Z GFS IS
IN VERY GOOD AGREEMENT WITH THE PREVIOUS 00Z RUN, WHICH IS ALSO
REFLECTED IN CURRENT WIND GRIDS INTO THE WEEKEND. THE 12Z SEA
STATE ANALYSIS INDICATED THAT OBSERVED SEAS WERE IN LINE WITH THE
CURRENT WAVE GRIDS, WITH MAXIMUM OF AROUND 8 FT OVER THE NORTHERN
NT2 WATERS WITH SEAS IN THE 2 TO 6 FT RANG OVER THE REMAINDER OF
AREA. NO CHANGES ARE ALSO PLANNED FOR THE WAVE GRIDS.
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PREVIOUS DISCUSSION...
THE 06Z PRELIMINARY OPC-NCEP SURFACE ANALYSIS SHOWS A 1023 MB
HIGH PRESSURE AREA CENTERED OVER THE FAR SE PART OF THE OFFSHORE
WATERS, WELL OFF THE GEORGIA AND S. CAROLINA COASTS. A NEARLY
STATIONARY FRONT WAS LOCATED FROM THE NEW JERSEY COAST E AND SE
OVER THE NORTHERN NT2 WATERS. THE FRONT IS STILL FORECAST TO
LIFT N AS A WARM FRONT TODAY AS LOW PRESSURE AREAS TRACK EASTWARD
FROM FAR SOUTHERN NEW ENGLAND. THE FRONT WILL PERSIST ROUGHLY
ALONG 40N OF SO TONIGHT INTO THU AS ANOTHER LOW TRACKS E ALONG
THE FRONT. THE FRONT WILL LIKELY THEN LIFT FURTHER N LATER THU
INTO THU NIGHT AS A STRONG COLD FRONT AND STRENGTHENING LOW
PRESSURE AREA APPROACHES THE WATERS FROM THE W. THE STRENGTHENING
LOW WILL LIKELY CROSS THE GULF OF MAINE EARLY FRI WITH A STRONG
COLD FRONT TRAILING S AND SW FROM THE LOW TO WATERS JUST OFF MOST
OF THE EASTERN SEABOARD. THE LOW WILL TRACK NE OVER NOVA SCOTIA
FRI WITH THE FRONT CROSSING THE REMAINDER OF THE WATERS. A
SECONDARY COLD FRONT WILL DEVELOP AND CROSS MOST OF THE REGION
FRI NIGHT INTO SAT, WITH CONDITIONS IMPROVING FROM W TO E SAT
AFTERNOON AS HIGH PRESSURE BUILDS E TOWARD THE COAST AND THE
SECONDARY FRONT PASSES E OF THE WATERS. THERE WILL BE A THREAT
FOR THUNDERSTORMS MAINLY NEAR THE FRONTAL SYSTEM OFF THE NEW
JERSEY AND NEW ENGLAND COAST TODAY INTO THU NIGHT, AND THEN
AHEAD OF THE STRONG COLD FRONT OVER MOST OF THE WATERS LATER THU
NIGHT THROUGH FRI INTO FRI NIGHT. MARINERS SHOULD USE CAUTION IN
AND NEAR ANY OF THE HEAVIER THUNDERSTORMS THAT DEVELOP ACROSS THE
WATERS THROUGH FRI INTO FRI NIGHT, WITH THE HEAVIER THUNDERSTORMS
HAVING THE POTENTIAL TO PRODUCE WINDS EXCEEDING GALE FORCE AND
VERY ROUGH WAVES.
OVERALL THEN FOR TODAY INTO SAT, AS THE 00Z GUIDANCE HAS COME
INTO VERY GOOD AGREEMENT. WE WILL POPULATE GRIDS WITH 3:1 BLEND
OF THE 00Z GFS FIRST SIGMA LAYER WINDS AND PREVIOUS GRIDS. THIS
WILL SERVE TO EXPAND GALES FROM THE PAST FEW OPC FORECASTS OVER
THE WATERS, WITH WINDS UP TO 40 TO 45 KT POSSIBLE MAINLY NEAR THE
GULF STREAM BY FRI AHEAD OF THE STRONG COLD FRONT, AND THEN
AGAIN BY EARLY SAT IN THE STRONG COLD AIR ADVECTION IN THE WAKE
OF THE FRONT AND A SECONDARY COLD FRONT CROSSING THE WATERS. OVER
THE PAST SEVERAL WEEKS IT DOES APPEAR THAT THE HIGHER FIRST
SIGMA LAYER WINDS FROM THE GFS DO TEND TO VERIFY BETTER THAN THE
REMAINING GUIDANCE, ESPECIALLY IN THE STRONG COLD ADVECTION
BEHIND COLD FRONTS. STORM FORCE GUSTS ARE ALSO POSSIBLE AGAIN
MAINLY NEAR THE GULF STREAM BY FRI INTO SAT, WITH MARINERS URGE
TO USE CAUTION ESPECIALLY DURING THIS TIME PERIOD. AT ANY RATE,
THE GALES WILL THEN LIKELY BEGIN SHIFTING TO THE FAR EASTERN
PARTS OF THE NORTHERN NT2 WATERS BY LATER SAT AS HIGH PRESSURE
BUILDS TOWARD THE COAST AND COLD AIR ADVECTION DIMINISHES.
FOR SAT NIGHT AND SUN, WE WILL POPULATE GRIDS WITH A 1:1 BLEND OF
00Z ECMWF WINDS AND 00Z FIRST SIGMA LAYER GFS WINDS. THIS ALLOWS
ANY GALES WHICH LINGER OVER THE OUTER NORTHERN NT2 WATERS NEAR
THE GULF STREAM TO SHIFT E, WITH HAZARDS ENDING EARLY SAT NIGHT,
WITH HIGH PRESSURE SLIDING ACROSS THE WATERS AND IMPROVING
CONDITIONS OVER MOST AREAS SAT NIGHT AND SUN.
FINALLY, FOR SUN NIGHT AND THEREAFTER, WE WILL TREND GRIDS CLOSER
TO THE MIDDLE OF THE ROAD 00Z ECMWF SOLUTION, WHICH MAINTAINS A
WEAKENING RIDGE WESTWARD OVER THE SOUTHERN NT2 WATERS AS A COLD
FRONT MOVES SE FROM THE GREAT LAKES INTO NEW ENGLAND.
SEAS
WAVE HEIGHTS HAVE RISEN TO NEAR 9 FT NEAR THE NORTH WALL
OF THE GULF STREAM PER THE LATEST OBSERVATIONS. THE 00Z ECMWF WAM
APPEARS TO HAVE INITIALIZED FAIRLY CLOSE TO THE OBSERVATIONS OVER
THE AREA EARLY TODAY. WE WILL POPULATE THE WAVE HEIGHT GRIDS WITH
THE 00Z WAM FOR TODAY, AND ADD UP TO 10 PERCENT OR SO NEAR THE
GULF STREAM. FOR TONIGHT THROUGH SUN, WE WILL POPULATE GRIDS WITH
A 2:1 BLEND OF THE PREVIOUSLY ENHANCED WAVE HEIGHT GRIDS, AND THE
00Z WAM, AND THEN FOR SUN NIGHT INTO NEXT WEEK TRANSITION TOWARDS
THE 00Z WAM GUIDANCE.
EXTRATROPICAL STORM SURGE GUIDANCE
NO SIGNIFICANT POSITIVE
SURGE EVENTS ARE EXPECTED DURING THE NEXT COUPLE OF DAYS. PLEASE
MONITOR PRODUCTS FROM COASTAL NATIONAL WEATHER SERVICE OFFICES
FOR DETAILED WATER LEVEL INFORMATION.
WARNINGS
PRELIMINARY.
NT1 NEW ENGLAND WATERS
ANZ805...GEORGES BANK WEST OF 68W
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ810...SOUTH OF NEW ENGLAND
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ815...SOUTH OF LONG ISLAND
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
NT2 MID-ATLANTIC WATERS
ANZ820...HUDSON CANYON TO BALTIMORE CANYON
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ915...HUDSON CANYON TO THE GREAT SOUTH CHANNEL
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY INTO SATURDAY.
ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY INTO SATURDAY.
ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY INTO SATURDAY.
ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY INTO SATURDAY.
ANZ825...INNER WATERS FROM BALTIMORE CANYON TO CAPE CHARLES LIGHT
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY NIGHT.
ANZ828
INNER WATERS FROM CAPE CHARLES LIGHT TO CURRITUCK BEACH LIGHT...
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY INTO FRIDAY NIGHT.
ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY INTO SATURDAY.
ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY.
ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY.
ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR
GALE THURSDAY NIGHT.
GALE POSSIBLE FRIDAY.
.FORECASTER KOSIER/MILLS. OCEAN PREDICTION CENTER.
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