marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 820 PM EST Sat 23 Feb 2019
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
At 00z 1018 mb low pressure was centered near Cape Hatteras with a warm front extending southeast from the low across the offshore waters. A coastal front was also draped just northwest of the low and northeast over the central nt2 waters. The latest models continued to be quite consistent with the developing coastal surface low and strong cold front which will impact the nt2/nt1 offshore waters the remainder of the weekend and early next week. The models also continue to share a similar timing with the front and widespread gales developing ahead of the cold front before daybreak sun, and winds further increasing (likely to storm force across Georges Bank and the outer northern nt2 zones Mon into Mon night) in the cold air advection in the wake of the cold front Sun night and Mon. As has been the case for the last couple days, the 18z GFS and 18z fv3-GFS were somewhat stronger than the remaining global guidance with the winds in the cold air advection. Based on the most recent high resolution guidance, we plan to move up the onset of the southerly gales over the outer central nt2 waters by about three hours. Otherwise, the previous wind grids look very representative, and we will not be making any changes with this evenings updates. Both the wavewatch and ECMWF wam are equally well initialized with the wave heights across the offshore and coastal waters this evening.
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Over the short term, little change to the ongoing opc grids appears necessary, and we will populate grids with a 50/50 blend of the previous grids and 12z warw winds tonight through Sun night to refresh the forecast, and adjust winds slightly (adding around 10 percent), especially near the north and west walls of the Gulf Stream, in order to maintain the previous hazards over the short term. Ascat overpasses from around 1450z this morning indicated winds up to 25 kt or so mainly S of Hatteras Canyon, with winds up to 20 kt N of Hatteras Canyon, closer to the center of the high pressure area crossing the New England and northern mid-Atlantic offshore waters. We still expect gale force winds to develop early sun as developing low pressure along a warm front tracks NE from near Delaware Bay, with the best chance for gales near the north and west walls of the Gulf Stream or zones anz920 and 910, southwestward to E of Cape Fear. Gales are still forecast to develop over New England waters Sun afternoon as the low strengthens rather rapidly as it moves NE along the coast. As the intensifying low lifts NE toward the Canadian Maritimes Sun night a strong cold front will sweep E and se over the region. Strong cold air advection developing in the wake of the strong cold front will allow gales to increase in areal coverage Sun night with solid 40 kt gales likely as a strong 925 mb winds up to 60 kt or so cross waters especially N of Cape Hatteras. Storm force winds appear as if they will hold off until during the day Mon as was described in the previous few opc forecasts. Overall, forecast confidence over the short term is above average.
Over the medium range, we will bring storm force winds to the offshore waters by Mon afternoon, or similar to the past few opc forecasts, with the 12z model guidance remaining consistent and in good agreement over the region Mon into early Thu. The storm force winds will gradually end from W to E Mon night, with gale force winds lingering and only slowly diminishing from W to E Tue into Wed night as a large low pressure system slowly lifts NE from the Canadian Maritimes, and high pressure slowly builds E and se toward the region from the Midwest. For Mon into early Thu, we will populate grids with a 50/50 blend of the previous grids and boosted 12z ECMWF winds, with no major change from the past few opc forecasts Mon into early Thu. For most of the day Thu into next weekend we will trend our grids more toward the 12z ECMWF solution for now, and cap winds at 30 kt as forecast confidence diminishes with time, beginning on Thu. This idea is also supported to some extent by the latest wpc medium range guidance, and the overall trend noted in most of the 12z models and their respective ensemble means as well. High pressure is forecast to finally build E over especially New England and the northern mid-Atlantic offshore waters Thu into Thu night as an inverted trough or weak frontal/low pressure system forms off the se U.S. Coast. Additional adjustments to the mid to late week offshore forecast are likely over the next few days. Please closely monitor the latest opc forecast.
Seas: sea heights range from 8 ft or so off the north and South Carolina coasts this afternoon to 3 ft or less off the New England and northern mid-Atlantic coasts, with both the 12z ECMWF wam and 12z wavewatch initializing quite well this afternoon over the region. For the afternoon package, we will populate grids with a 20 percent previous grid, 80 percent 12z ECMWF wam blend for tonight into early Thu, and then trend grids more toward the 12z wam model output, and cap sea heights at 12 ft or so later in the week to match the capped winds. This will tend to result in no major change for the afternoon package from the past few opc forecasts for most of the upcoming week.
.Extratropical storm surge guidance...The 12z estofs, like the 00z estofs, continues to show surge values around 1 to 1.5 ft over the southern and northern New England coasts sun into Sun night as the onshore flow north of the warm front increases. The 12z etss is remaining well below 1 ft, except near the eastern coast of Maine and Bay of Fundy where it shows surge up to 1.5 to 2 ft sun evening. The etss still appears too low at least across Long Island Sound. The models do indicate any surge should be relatively short lived which seems reasonable given the rapid northward movement of the warm front and strong easterly winds. For more details please monitor the latest forecast and information from your local National Weather Service office.
.Nt1 New England waters... .anz800...Gulf of Maine... gale Sunday into Monday. Storm possible Monday night. Gale possible Tuesday into Wednesday. .Anz805...Georges Bank west of 68w... gale Sunday into Sunday night. Storm Monday. Storm possible Monday night. Gale possible Tuesday into Wednesday. .Anz900...Georges Bank east of 68w... gale Sunday night. Storm Monday. Storm possible Monday night. Gale possible Tuesday into Wednesday night. .Anz810...South of New England... gale Sunday night. Storm Monday. Gale possible Monday night into Tuesday night. .Anz815...South of Long Island... gale Sunday night into Monday. Gale possible Monday night.
.Nt2 mid-Atlantic waters... .anz820...Hudson Canyon to Baltimore Canyon... gale Sunday night into Monday. Gale possible Monday night. .Anz915...Hudson Canyon to the great South Channel... gale Sunday night. Storm Monday. Gale possible Monday night into Tuesday night. .Anz920...Baltimore Canyon to the great South Channel... gale tonight into Monday. Gale possible Monday night into Tuesday night. .Anz905...The great South Channel to the Hague line... gale Sunday night. Storm Monday. Storm possible Monday night. Gale possible Tuesday into Wednesday night. .Anz910...East of the great South Channel and south of 39n... gale Sunday into Sunday night. Storm Monday. Storm possible Monday night. Gale possible Tuesday into Wednesday night. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale Sunday into Monday. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale Sunday into Monday. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale tonight into Monday. Gale possible Monday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale Sunday into Monday. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale Sunday into Sunday night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale Sunday into Monday. .Anz835...Inner waters from Cape Fear to 31n... gale Sunday into Sunday night. .Anz935...Outer waters from Cape Fear to 31n... gale Sunday into Sunday night.
.Forecaster Clark/Mills. Ocean prediction center.