marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 347 PM EST Tue Jan 15 2019
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Per the 18z NCEP surface analysis a high pressure ridge was located over the opc offshore waters. Available ascat wind retrievals indicated 10-20 kt winds over the offshore waters. The 12z guidance was in good agreement through Thu 12z, so feel it's reasonable to populate the grids through that time period with the 12z GFS. High pressure over the offshore waters generally remains in place through early Thu, except over the nt1 and N portions of the nt2 waters Wed and Wed night as a cold front approaches, then passes E through those aforementioned regions Wed night into Thu morning. Guidance continues to remain in very good agreement concerning the timing and strength of the frontal passage. Continue to anticipate the strongest winds ahead and behind the front to be over the nt1 waters, especially over the Gulf of main I will keep winds at or near 30 kt overnight Wed into early Thu immediately behind the front.
High pressure rebuilds over the nt1 and N nt2 waters behind the front before the next system near the E coast Fri. Guidance remains divergent regarding this particular low pressure system, which is expected to pass E through the waters in the Fri through early Sat time frame. The 12z GFS is farther N and moves the low center E across the nt1 waters, whereas the 12z ECMWF/UKMET are farther S with a track through the N nt2 waters instead. Though by Sat morning the guidance comes somewhat back into better agreement, placing the low just S of Nova Scotia by then. With these continued differences noted, feel it's best to continue with the old grids and hence a persistence forecast from Thu 15z through sun 12z. Will continue to monitor trends in the guidance over the next several runs to see if they come to a better consensus. That said, despite the differences concerning the track, guidance right now agrees winds associated with the low will remain sub-gale. None the less we will continue to watch for any trends in regards to the warning level aspect as well.
Attention then turns to strong low pressure and its accompanying strong cold front nearing the E coast late Sat into day 5 sun before pushing E across the entire opc offshore zones sun and Sun night. There are some differences noted among the guidance concerning the exact track of the parent low and timing of the frontal passage, with the 12z GFS the farthest NE with the low center, and the 12z ECMWF/UKMET slower, both placing the low the Appalachian Mountains sun. The 12z CMC/navgem are in between both camps, with the low over Virginia, though the position of the cold front lines up well with the GFS solution. The 12z GFS/CMC/navgem maintain similar agreement in terms of how fast they move through front E through the waters by Sun night, with the 12z ECMWF coming into better agreement by then as well, though a bit slower than the GFS/CMC/navgem, with the UKMET lagging behind. Will make the choice to populate the grids on sun and Sun night with the 12z GFS, though with confidence being a bit below average concerning the timing of the front just due to some of the aforementioned differences the 12z ECMWF/UKMET show. That said while differences are noted in the timing of the front, there is agreement among the models on its strength and the development of widespread S to SW gales ahead of the front sun, then NW gales in the cold air advection in the wake of the front. This has remained consistent when looking at the various model cycles since at least yesterday. With this noted plus the consistency seen at least in terms of the idea of a strong front pushing offshore late Sat into Sun night, I feel there's reasonable enough support to introduce widespread gales sun and Sun night across the opc offshore waters, despite it being day 5. Only change here will be to cap winds at 40 kt as the 12z GFS had some areas of 45 kt winds in the S to SW flow and I don't want to go that high as of now. We will continue to monitor the trends over the rest of the week in order to make adjustments as needed to the coverage and duration of the gale as needed.
.Seas...Will favor the 12z wavewatch iii guidance through Thu 12z given the choice to use the 12z GFS, then allow the old grids to remain in place through sun 12z, before using the 12z wavewatch iii through the end of the period. For sun, decreased the wave heights by about ten percent or so where GFS winds were decreased.
.Extratropical storm surge guidance...No significant positive surge events appear likely for the next few days.
.Nt1 New England waters... .anz800...Gulf of Maine... gale possible Sunday into Sunday night. .Anz805...Georges Bank west of 68w... gale possible Sunday into Sunday night. .Anz900...Georges Bank east of 68w... gale possible Sunday into Sunday night. .Anz810...South of New England... gale possible Sunday into Sunday night. .Anz815...South of Long Island... gale possible Sunday into Sunday night.
.Nt2 mid-Atlantic waters... .anz820...Hudson Canyon to Baltimore Canyon... gale possible Sunday into Sunday night. .Anz915...Hudson Canyon to the great South Channel... gale possible Sunday into Sunday night. .Anz920...Baltimore Canyon to the great South Channel... gale possible Sunday into Sunday night. .Anz905...The great South Channel to the Hague line... gale possible Sunday into Sunday night. .Anz910...East of the great South Channel and south of 39n... gale possible Sunday into Sunday night. .Anz825...Inner waters from Baltimore Canyon to Cape Charles Light... gale possible Sunday into Sunday night. .Anz828...Inner waters from Cape Charles Light to Currituck Beach Light... gale possible Sunday into Sunday night. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale possible Sunday into Sunday night. .Anz830...Inner waters from Currituck Beach Light to Cape Hatteras... gale possible Sunday into Sunday night. .Anz833...Inner waters from Cape Hatteras to Cape Fear... gale possible Sunday into Sunday night. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale possible Sunday into Sunday night. .Anz835...Inner waters from Cape Fear to 31n... gale possible Sunday. .Anz935...Outer waters from Cape Fear to 31n... gale possible Sunday into Sunday night.
.Forecaster Holley. Ocean prediction center.