247
AGNT40 KWNM 290144
MIMATN
MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
944 PM 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.
THE LATEST NCEP SURFACE ANALYSIS SHOWS A FRONTAL BOUNDARY ACROSS
THE NT1 OFFSHORE WATERS THIS EVENING, AND A HIGH PRESSURE RIDGE
OVER THE SRN NT2 ZONES. IN BETWEEN THE TWO FEATURES, THE ANALYSIS
SHOWS A TIGHTENED PRESSURE GRADIENT ACROSS THE NRN NT2 WATERS,
INDICATING ENHANCED SW FLOW ACROSS THE GULF STREAM. ASCAT WIND
RETRIEVALS FROM 14Z THIS MORNING SHOWED WINDS TO 30 KT IN THIS
REGION AHEAD OF THE FRONT, AND A VERY RECENT PASS FROM AROUND 23Z
THIS EVENING INDICATES ABOUT THE SAME TO THE E OF THE OFFSHORE
WATERS. THIS MATCHES UP WELL WITH THE PREVIOUS WIND GRIDS, AND
THE 12Z/18Z MODELS AGREE ON 30 KT MAX WINDS IN THIS REGION FOR
TONIGHT AND THU AS A FRONTAL WAVE DEVELOPS TO THE E OF THE
REGION. THE MODELS DO SHOW HIGHER WINDS JUST ABOVE THE SURFACE
OVER THE WARMER SSTS, WITH GFS/ECMWF 925 MB WINDS INDICATING 40
KT OVER THE GULF STREAM IN NRN NT2. ALTHOUGH WOULD NOT RULE OUT
AN OCCASIONAL GALE FORCE GUST MIXING TO THE SURFACE, AM NOT
EXPECTED SUSTAINED GALES FOR TONIGHT INTO THU AS THE MODELS ARE
NOT SUPPORTING THAT SCENARIO. AS SUCH, AM PLANNING ON KEEPING MAX
WINDS AT 30 KT FOR TONIGHT INTO THU.
THE MODELS THEN SHOW AN ACTIVE PATTERN CONTINUING OVER THE
OFFSHORE WATERS THROUGH THE REMAINDER OF THE FORECAST PERIOD,
WITH THE GUIDANCE HAVING A STRONG SIGNAL FOR THE DEVELOPMENT OF
GALE FORCE CONDITIONS IN THE SW FLOW AHEAD OF THE NEXT COLD
FRONT THU NIGHT AND FRI, AND THEN IN THE COLD AIR ADVECTION
BEHIND THE FRONT FRI NIGHT AND SAT. THE PREVIOUS FORECAST HAD
GALE HEADLINES UP WITH THIS SYSTEM CONSISTENT WITH THE GFS WINDS,
AND CONFIDENCE REMAINS ABOVE AVERAGE WITH THEM AS A RESULT OF THE
STRONG CONSENSUS. AS SUCH, AM PLANNING ON CONTINUING WITH THEM IN
THE UPDATE PACKAGE.
THE GFS THEN SHOWS ANOTHER STRONG COLD FRONT MOVING ACROSS THE W
ATLC SUN AND SUN NIGHT, AND AGAIN SHOWS ANOTHER ROUND OF GALES
DEVELOPING AHEAD OF IT. HOWEVER, THE REST OF THE MODELS ARE MUCH
WEAKER WITH THE WINDS THAN THE GFS, SO CONFIDENCE IS BELOW
AVERAGE ON THE PROSPECT OF GALES WITH THIS SYSTEM. THE PREVIOUS
FORECAST WENT UP TO 25 KT FOR SUN AND SUN NIGHT, WHICH SEEMS
REASONABLE CONSIDERING THE LARGE SPREAD IN THE MODELS. AS SUCH,
AM PLANNING ON STAYING NEAR THIS INTENSITY FOR THE UPDATE
PACKAGE, AND WILL OTHERWISE NOT BE CHANGING MUCH THROUGH THE
REMAINDER OF THE FORECAST PERIOD.
-----------------------------------------------------------------
PREVIOUS DISCUSSION...
THE 18Z PRELIMINARY SURFACE ANALYSIS INDICATED A WARM FRONT
EXTENDING ACROSS THE CENTRAL NEW ENGLAND WATERS AND THE FAR
NORTHEAST MID ATLANTIC WATERS. HIGH PRESSURE WAS CENTERED NEAR
32N69W WITH RIDGE EXTENDING WEST ACROSS THE CENTRAL AND SOUTHERN
MID ATLANTIC WATERS. THE LATEST ASCAT PASSES FROM BETWEEN 1355Z
AND 1510Z INDICATED AN AREA OF 25 TO 30 KT WINDS OVER THE CENTRAL
NT2 WATERS BETWEEN 38N AND 35N. WINDS OVER THE REMAINDER OF THE
AREA RANGED FROM 5 TO 10 KT OVER THE NT1 WATERS TO 10 TO 20 KT
OVER THE REMAINDER OF THE NT2 WATERS.
THE 12Z MODELS ARE IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD
WITH ONLY MINOR DETAIL DIFFERENCES NOTED. THE MAIN FORECAST
CONCERN IS FROM THURSDAY EVENING AND CONTINUING THROUGH SATURDAY
EVENING AS SEVERAL STRONG COLD FRONTS MOVE ACROSS THE AREA. THE
INITIAL FRONT WILL MOVE ACROSS THE AREA THURSDAY NIGHT INTO
FRIDAY AS LOW PRESSURE MOVES ACROSS THE GULF OF MAINE. THE SECOND
FRONT WILL THEN MOVE ACROSS THE WATERS FRI NIGHT. STILL HAVE
ABOVE AVERAGE CONFIDENCE IN SOUTHWESTERLY GALES IN ADVANCE OF THE
FIRST FRONT THURSDAY NIGHT INTO FRIDAY OVER THE NORTHERN AND
CENTRAL NT2 WATERS, WITH NORTHWEST GALES IN THE COLD ADVECTION
FOLLOWING THE SECOND FRONT FRIDAY NIGHT THROUGH SATURDAY EVENING.
ALL OF THE MODELS ARE IN GOOD AGREEMENT WITH THE TIMING AND
PLACEMENT OF THE GALES, AND FOR THE WIND GRIDS WILL INITIALLY USE
THE GFS FIRST SIGMA LEVEL WINDS THROUGH 00Z FRIDAY AS THEY SEEM
TO BE VERIFYING BETTER BASED ON ASCAT. WILL THEN USE AN EVEN
BLEND OF THE 12Z FIRST SIGMA LEVEL WINDS AND PREVIOUS GRIDS WHICH
WILL RESULT IN NO CHANGES TO EXISTING WARNING HEADLINES. A HIGH
FOR SUNDAY AND BEYOND, A HIGH PRESSURE RIDGE WILL BUILD TOWARDS
THE AREA SUNDAY, THEN PASS EAST OF THE WATERS SUNDAY NIGHT AS A
WARM FRONT APPROACHES THE AREA. THE WARM FRONT WILL THEN MOVE
ACROSS THE NT1 WATERS MONDAY AND MONDAY NIGHT, AND ALL THE
MODELS KEEP WINDS BELOW GALE LEVELS. USED AN EVEN BLEND OF THE
PREVIOUS GRIDS WHICH WERE BASED ON THE 00Z ECMWF, AND THE 12Z
ECMWF.
SEAS
THE 18Z SEA STATE ANALYSIS INDICATED THAT OBSERVED SEAS
CONTINUE TO MATCH UP WELL WITH THE CURRENT WAVE GRIDS. WENT WITH
11 FT MAX OVER THE NORTHERN NT2 WATERS NEAR GULF STREAM.
OTHERWISE, SEAS RANGED FROM 3 TO 6 FT OVER THE NT1 AND CENTRAL
AND SOUTHERN NT2 WATERS, TO 6 TO 11 FT OVER THE NORTHERN NT2
WATERS. FOR TONIGHT THROUGH SUNDAY NIGHT WILL MAINTAIN THE
PREVIOUS WAVE GRIDS WHICH WERE BASED ON THE 00Z ECMWF WAM AND
BOOSTED FOR GALE AREAS. FOR SUNDAY NIGHT AND BEYOND WILL USE THE
12Z ECMWF WAM.
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 INTO FRIDAY.
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL
GALE THURSDAY NIGHT INTO FRIDAY.
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE
GALE THURSDAY NIGHT INTO FRIDAY.
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N
GALE THURSDAY NIGHT INTO FRIDAY.
GALE POSSIBLE FRIDAY NIGHT 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 INTO FRIDAY.
GALE POSSIBLE FRIDAY NIGHT.
ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON
GALE THURSDAY NIGHT INTO FRIDAY.
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS
GALE THURSDAY NIGHT INTO FRIDAY.
ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR
GALE THURSDAY NIGHT INTO FRIDAY.
ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR
GALE THURSDAY NIGHT INTO FRIDAY.
.FORECASTER KELLS/KOSIER. OCEAN PREDICTION CENTER.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page