AGNT40 KWNM 311325 MIMATN Marine Weather Discussion for N Atlantic Ocean NWS Ocean Prediction Center Washington DC 925 AM EDT Sun May 31 2020 .FORECAST DISCUSSION...Major features/winds/seas/significant .weather for the North Atlantic Ocean W of 50W from 30N to 50N. A cold front inland across the region will slowly move east of the waters in the short term and high pressure will build behind the front with its center moving across the southern waters in the extended period. Low pressure will form along the front just east of the waters and track northeast forcing a tight pressure gradient over the central waters with northwest winds increasing over the outer waters. Latest NCEP weather map has a cold front that stretches from northeastern Canada through Baltimore canyon to the southeastern states while high pressure 1027 Mb is near 35N50W. Another high pressure 1029 Mb is centered over the great lakes region. Pressure gradient is fairly relaxed across the waters. There are no major changes depicted by models and so will not deviate much from previous forecast and will retain all warnings following GFS model guidance. Seas are relatively small across the forecast waters and they range between 6 and 8 ft over the northeastern waters in the vicinity of the gulf stream and they are less than 6 ft elsewhere. NWW3 and ECMWFWAVE wave models are close to the observed seas. In the short term, both wave models agree on keeping relatively small seas over the southern waters. The only differences are when relatively large seas gradually shift to the north in response to the increased winds. NWW3 has slightly larger seas and that matches well with the winds. Will therefore use WAN for seas. ----------------------------------------------------------------- PREVIOUS DISCUSSION... Over the short term, today through Tue, hazard-level winds are not expected outside of the locally stronger winds near gale force or possibly higher in and near thunderstorms, which will be the most likely over the southern and central NT2 waters and outer northern NT2 waters today, and then becoming confined to the southern NT2 waters tonight. The stronger thunderstorms early this morning are located from S of Georges Bank southwestward across all but the NW part of the NT2 waters, per the latest lightning data and GOES-IR satellite imagery. ASCAT data from last evening indicated several areas of SW winds to 25 kt over the same general area depicted above and associated with the scattered thunderstorm convection. The 06Z preliminary OPC-WPC surface analysis shows a cold front extending from a 1006 mb low on the Maine coast southwestward to the North Carolina coast, and then further SW over areas just inland over eastern portions of South Carolina and Georgia, with the front moving off to the E and SE. Also, a 1014 mb low was located about 350 nm E of Bermuda moving slowly N. This low now has a near zero percent chance for additional sub-tropical storm development per the 2 AM EDT Tropical Weather Outlook from NHC, with the low forecast to remain well E of the offshore waters today into tonight before it dissipates Mon. Otherwise, we still expect the cold front to clear E of the offshore waters tonight, with high pressure building E and SE over the waters in the wake of the front overnight through Mon night into Tue, finally moving E of the NT2 waters later Tue as a warm front and low pressure area approaches the region from the W and NW. For the short term part of the forecast we will continue to populate grids with the consistent 00Z GFS winds, and run the stability tool which will place the stronger first sigma layer winds over the unstable areas, which will be closer to the gulf stream, and the lower 10 meter winds elsewhere. A low will likely form along the cold front to the E of the offshore waters Mon into Tue, with a threat for gales developing near the low by Mon night into Tue, E of the northern NT2 and New England waters. For more information regarding this low and associated conditions please refer to the high seas forecast, HSFAT1. Forecast confidence levels will be above average over the short term. Over the medium range, forecast confidence becomes near average, with some divergence noted in the 00Z global models. For the most part, the 00Z ECMWF has remained quite consistent, and we will transition grids mostly toward the ECMWF winds for Tue night and beyond. We will also use the bias-corrected ECMWF winds for this time frame which will lead to more widespread gales occurring mostly over the outer northern NT2 waters by later Tue night, continuing into Wed and Thu before these stronger winds shift E of the offshore waters. We feel confident enough to expand the gales somewhat at this time, as the GFS and UKMET guidance has trended more toward the ECMWF solution, which is also close to the latest WPC medium range forecast. A warm front will lift east and northeastward across northern NT2 and NT1 waters later Tue night and Wed, as low pressure tracks E over northern New England. The low will move slowly E and NE Wed night into Thu as it crosses far SE Canada and then the Canadian Maritimes. A cold front associated with the low will move toward the New England and northern Mid-Atlantic coast early Thu, then slowly cross these waters later Thu into Thu night, as a high pressure ridge prevails over the far southern NT2 waters. Seas: For the early morning package, over the short term part of the forecast to best match the winds we will rely on the 00Z Wavewatch model output as it appears to be verifying fairly well over the offshore waters, although it may be a ft or two too low over the waters near the north wall of the gulf stream, per the latest altimeter data which shows seas rising to near 9 ft over this region early this morning. We will, therefore, add up to 10 to 15 percent near the north wall today and tonight into Mon. By Tue night and thereafter, we will transition grids closer to the 00Z ECMWF WAM guidance to best match the wind forecast at that time. .EXTRATROPICAL STORM SURGE GUIDANCE...Significant positive surge events do not appear likely over the next few days. Consult your local National Weather Service forecast office for more information. .WARNINGS...Preliminary. .NT1 New England Waters... .ANZ900...Georges Bank east of 68W... Gale Possible Wednesday night. .NT2 Mid-Atlantic Waters... .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 Thursday. .ANZ905...The Great South Channel to the Hague Line... Gale Possible Wednesday into Thursday. .ANZ910...East of the Great South Channel and south of 39N... Gale Possible Tuesday night into Thursday. .ANZ828...Inner Waters from Cape Charles Light to Currituck Beach Light... Gale Possible Wednesday night. .ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon... Gale Possible Tuesday night into Wednesday night. .ANZ830...Inner Waters from Currituck Beach Light to Cape Hatteras... Gale Possible Wednesday into Wednesday night. $$ .Forecaster Musonda/Mills. Ocean Prediction Center.