103
AGNT40 KWNM 280126
MIMATN
MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
926 PM EDT TUE APR 27 2021
FORECAST DISCUSSION
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.
NO MAJOR CHANGES TO THE ONGOING OPC FORECAST APPEAR NEEDED FOR
THE EVENING UPDATE. WE WILL ADD IN THE POSSIBLE GALES TO THE
WATERS JUST EAST AND NORTHEAST OF CAPE HATTERAS BY AROUND 00Z
FRI, OR 3 HOURS OR SO EARLY THAN THE PREVIOUS FEW OPC FORECASTS,
BASED ON THE LATEST SET OF GUIDANCE. OTHERWISE, WE WILL MAKE ONLY
A FEW MINOR EDITS IN DEFERENCE TO NEARBY TAFB AND COASTAL WFO
GRIDDED FORECASTS OVER THE NEXT FEW DAYS. A WARM FRONT EXTENDING
SE FROM THE JERSEY SHORE WILL LIFT NE INTO SOUTHERN NEW ENGLAND
WATERS AND STALL WITH LOW PRESSURE CENTERS TRACKING E ALONG THE
STALLED BOUNDARY WED THROUGH THU. THE TIMING OF THE LATE WEEK
STRONGER COLD FRONT IS STILL SOMEWHAT IN QUESTION THIS EVENING.
AS A RESULT, WE WILL NOT ALTER THE FORECAST FOR LATE IN THE WEEK
UNTIL A FULL SUITE OF 00Z MODELS ARRIVE LATER THIS EVENING AND
OVERNIGHT.
SEAS: WAVE HEIGHTS RANGE FROM AROUND 7 FT OR SO E OF THE VIRGINIA
CAPES WHERE SW WINDS ARE BEGINNING TO INCREASE NEAR THE WARM
FRONT MENTIONED ABOVE, WITH SEAS NEAR 8 FT OVER THE FAR NE NT2
WATERS, TO 3 FT OR SO OVER THE FAR WESTERN PART OF THE INNER
OFFSHORE WATERS PER THE LATEST OBSERVATIONS. NO MAJOR CHANGES TO
THE PREVIOUS WAVE HEIGHT FORECAST APPEARS NEEDED AT THIS TIME.
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PREVIOUS DISCUSSION...
AT 18Z, A LOW PRESSURE TROUGH WAS LOCATED NEAR THE NEW ENGLAND
COAST, WHILE A WARM FRONT WAS LOCATED JUST W OF THE SW NT2 WATERS
OVER CENTRAL NEW JERSEY. A 1024 MB HIGH SITUATED OVER THE S NT2
WATERS NEAR 33N73W, EXTENDED ITS RIDGE ACROSS BOTH THE NT1 AND
NT2 WATERS. HIRES ASCT DATA FROM NEAR 14-15Z INDICATED 15-25 KT
WINDS OVER THE FAR SE NT1 AND FAR NE NT2 WATERS E OF 67W, WHILE
5-15 KT WINDS WERE NOTED OVER THE INNER NT2 WATERS ROUGHLY
BETWEEN 73W AND 81W.
OVERALL THE 12Z GLOBAL MODELS FOLLOWED THE SAME TREND AS
OVERNIGHT WITH THE GUIDANCE BEING IN GOOD AGREEMENT THROUGH THU,
WITH THE GFS THEN BECOME THE OUTLIER IN TERMS OF BEING SLOWER
WITH THE STRONG COLD FRONT EXPECTED TO MOVE E THROUGH THE NT1 AND
NT2 WATERS THU NIGHT THROUGH FRI. HENCE FOR THIS FORECAST PACKAGE
I WILL USE A 1:1 BLEND OF THE OLD GRIDS AND 12Z GFS THROUGH THU
12Z, THEN A 1:1 BLEND OF THE OLD GRIDS AND 12Z ECMWF THROUGH THE
REST OF THE PERIOD, GIVEN THE GFS REMAINS AN OUTLIER. OVERALL,
THIS RESULTS IN NO SIGNIFICANT CHANGES TO THE WARNING HEADLINES
IN PLACE, EXPECTED WITH THE STRONG COLD FRONT TOWARDS THE END OF
THE WEEK.
THROUGH THU, HIGH PRESSURE REMAINS OVER THE CENTRAL AND S NT2
WATER, WHILE TO THE N A WARM FRONT BECOMES NEARLY STATIONARY BY
WED OVER THE S NT1 OR N NT2 WATERS, WITH SEVERAL LOW PRESSURE
WAVES MOVING E ALONG THE FRONT THROUGH THU. MODELS CONTINUE TO
AGREE ON ENHANCED WINDS OVER THE N NT2 WATERS IN THE TIGHT
GRADIENT BETWEEN THE FRONT TO THE N AND THE HIGH TO THE S, WITH
20-30 KT WINDS ANTICIPATED INTO THU NIGHT DUE TO THIS SYNOPTIC
SETUP. THE POSSIBILITY FOR GALES OVER THE WARMER SSTS ALONG THE
GULF STREAM OVER THE NE NT2 WATERS CANT COMPLETELY BE RULED
OUT, THOUGH RIGHT NOW ONLY THE 12Z ECMWF/UKMET BIAS CORRECTED
WINDS SEEM TO BE MOST BULLISH WITH ITS SPATIAL COVERAGE OF 30 KT
WINDS. SO IT IS SOMETHING THAT WILL BE MONITORED.
HEADING INTO THU, THE 12Z GLOBAL MODELS CONTINUE TO AGREE ON THE
IDEA OF A STRONG COLD FRONT, ASSOCIATED WITH STRONG LOW PRESSURE,
NEARING THE E COAST BY LATE THU. THE 12Z ECMWF/UKMET/CMC/NAVGEM
ARE ALL SIMILAR IN THEN MOVING THE LOW CENTER NE ACROSS THE NT1
WATERS THU NIGHT THROUGH FRI, WITH THE COLD FRONT MOVING E ACROSS
THE NT1 AND NT2 WATERS THU NIGHT INTO FRI. WHILE THE 12Z GFS HAS
A SIMILAR TRACK FOR THE LOW, IT CONTINUES TO BE THE SLOWER
SOLUTION BY ROUGHLY 12 HOURS OR SO. HENCE, THE REASON FOR IT
BEING DISCOUNTED FOR NOW AS IT WAS WITH THE OVERNIGHT FORECAST.
THE GLOBAL MODELS ARE IN AGREEMENT ON GALES DEVELOPING OVER THE
NT2 WATERS AHEAD OF THE FRONT THU NIGHT ALONG AND S OF THE GULF
STREAM, WITH THE GALES CONTINUING INTO FRI NIGHT, BEFORE THEY
BECOME NORTHWESTERLY LATE FRI NIGHT INTO EARLY SAT IN THE COLD
AIR ADVECTION ANTICIPATED BEHIND THE FRONT ONCE IT CLEARS THE
AREA. AT THE MOMENT WE CONTINUE TO HAVE GALES ENDING LATER SAT.
CONFIDENCE ON GALES ARE ABOVE AVERAGE GIVEN THE OVERALL MODEL
AGREEMENT AMONG THE 12Z ECMWF/UKMET/CMC/NAVGEM AND THE FACT THAT
EVEN WITH ITS SLOWER SOLUTION, THE 12Z GFS ALSO SUPPORTS GALES AS
WELL.
BEHIND THIS SYSTEM THE 12Z ECMWF/UKMET/CMC/NAVGEM ALL AGREE ON
HIGH PRESSURE MOVING INTO THE REGION AND BECOMING THE DOMINANT
SYNOPTIC FEATURE THROUGH THE WEEKEND. THE 12Z GFS IS AGAIN AN
OUTLIER HERE, AS ON SUN AND SUN NIGHT IT SUGGESTS LOW PRESSURE
MOVING OUT OF THE SE U.S. AND ALONG THE SE COAST BY SUN NIGHT.
THE FACT THE OTHER GLOBAL MODELS DONT SHOW THIS FEATURE, IS
WHY THE GFS WILL BE IGNORED HERE FOR NOW AS WELL.
SEAS
FOR SEAS I WILL FAVOR A 1:1 BLEND OF THE OLD GRIDS AND
12Z NOAA WAVEWATCH III THROUGH THU 12Z, THEN 2:1 BLEND OF THE OLD
GRIDS AND 12Z ECMWF WAM. SEAS WILL BE INCREASED BY 5-10 PERCENT
IN THE NEAR TERM OVER THE N NT2 WATERS IN THE PERSISTENT E WIND
FETCH DUE TO THE FRONT TO THE N AND HIGH TO THE SOUTH. A SIMILAR
PERCENTAGE INCREASE WILL BE INCLUDED IN AREAS OF GALES WITH THE
COLD FRONT SYSTEMS. ADDITIONALLY THIS INCREASE HELPS TO ACCOUNT
FOR ANY DAMPENING OF THE HIGHER SEA HEIGHTS FROM PREVIOUS
FORECASTS, DUE TO THE BLENDING.
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
NONE.
NT2 MID-ATLANTIC WATERS
ANZ915...HUDSON CANYON TO THE GREAT SOUTH CHANNEL
GALE POSSIBLE FRIDAY NIGHT INTO SATURDAY.
ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL
GALE POSSIBLE THURSDAY NIGHT INTO SATURDAY.
ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE
GALE POSSIBLE SATURDAY.
ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N
GALE POSSIBLE THURSDAY NIGHT INTO SATURDAY.
ANZ825...INNER WATERS FROM BALTIMORE CANYON TO CAPE CHARLES LIGHT
GALE POSSIBLE THURSDAY NIGHT.
ANZ828
INNER WATERS FROM CAPE CHARLES LIGHT TO CURRITUCK BEACH LIGHT...
GALE POSSIBLE THURSDAY NIGHT.
ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON
GALE POSSIBLE THURSDAY NIGHT INTO FRIDAY NIGHT.
ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS
GALE POSSIBLE THURSDAY NIGHT INTO FRIDAY.
ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR
GALE POSSIBLE THURSDAY NIGHT.
ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR
GALE POSSIBLE THURSDAY NIGHT INTO FRIDAY.
.FORECASTER MILLS/HOLLEY. OCEAN PREDICTION CENTER.
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