marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 258 am EST Thu Feb 23 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
The preliminary 06z opc-NCEP surface analysis shows a 1018 mb high pressure area centered 200 nm northwest of Bermuda moving eastward, with low pressure tracking slowly east from near Cape Canaveral, Florida. An evening ascat pass indicated winds to 20 kt occurring over southern nt2 waters, and winds of 15 kt or less elsewhere over the offshore waters. A complex low pressure system is moving northeast over the Great Lakes, per the 06z preliminary analysis.
The 00z global models are in pretty good agreement over the region for the next few days. The Florida low is forecast to track east and then turn northeast over the next few days, with marginal gales still forecast for southern nt2 waters later today into Friday, or similar to the previous forecast. The low will weaken some, and get pulled northward ahead of a strong cold front Friday into Saturday. There will be an area of gales form near the north wall of the Gulf Stream, or northeastern nt2 waters, on Saturday, or similar to the previous forecast. The 00z GFS has backed off somewhat with the extent of these gales, and for now, we will manually adjust grids slightly to keep the outer zone, anz910, in the gale force wind possible area for Saturday. The strong cold front is still forecast to reach western portions of the offshore waters later Saturday, and cross the remaining offshore waters Saturday night with the front passing east of the waters early Sunday. We will add a period of gales to central nt2 waters in the strong cold air advection behind the front Saturday night, mainly near the west and north walls of the Gulf Stream, or zones anz833, 830, 828 and 925. Confidence in the forecast today through Saturday night is near to above average. We will rely on the 00z GFS through Saturday night, and use the smart tool which places the stronger first sigma layer winds over unstable areas, and slightly lower 10 meter winds over stable areas.
High pressure will build east over the waters during Sunday and Sunday night allowing winds to diminish over the region. The 00z global models remain in decent agreement over the offshore waters Sunday into Sunday night, so we will remain close to the 00z GFS and continue to use the smart tool as noted previously. For later Sunday night into Monday we will trend the forecast toward the 00z ECMWF guidance. The high will likely strengthen as it crosses the region, with the high centered 100 to 200 nm north of Bermuda by Monday night. The 00z GFS appears to be too progressive with the high, and it also develops low pressure over nt1 waters later Monday night. The GFS is alone with this solution, with the ECMWF having good support from the UKMET, Canadian Gem, and navgem models. Confidence in the forecast from Sunday through Monday night is near average.
.Seas...Both the 00z wavewatch and ECMWF wam are initialized within a ft or so of the current data over the offshore waters. For the early morning package, with decent model agreement into Sunday night, we will use a 50/50 blend of the wavewatch and wam models. As we trend the forecast toward the 00z ecwmf for winds later Sunday night through Monday night we will also trend the sea height forecast toward the wam.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... .anz800...Gulf of Maine... gale possible Sunday into Sunday night.
.Nt2 mid-Atlantic waters... .anz910...east of the great South Channel and south of 39n... gale possible Saturday. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale possible Saturday night. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale possible Saturday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Saturday night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Saturday night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale Friday. .Anz835...Inner waters from Cape Fear to 31n... gale today into tonight. .Anz935...Outer waters from Cape Fear to 31n... gale tonight into Friday.
.Forecaster Mills. Ocean prediction center.