marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 106 PM PDT sun Aug 20 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
The 18z surface analysis indicated strong high pressure centered near 40n138w with ridge extending northeast to Vancouver Island, with low pressure inland over northern California. An ascat pass from 1802z indicated gales persisting over the far southeast Oregon offshore waters and the far northeast portion of the northern California waters. These gales extended east into the adjacent coastal waters.
The 12z models were all in very good agreement during the entire forecast period. The high pressure ridge will slowly weaken and shift southwest later tonight into Tuesday as a weak cold front approaches the Washington and Oregon waters Tuesday. Meanwhile, low pressure near the northern California coast will also weaken through Tuesday night. This will allow winds to decrease below gale by early Monday over the northern California and far southern Oregon waters. For the evening forecast issuance, plan on maintaining gales for pzz815 and pzz820 through about 06z with winds dropping below gale later tonight over the offshore waters while continuing over the coastal waters through late tonight. The weak cold front mentioned above will move across the Washington and Oregon waters Tuesday night through Wednesday before dissipating over the central California waters Thursday. The models also indicate the coastal trough slowly strengthening again Wednesday night through Friday night. This will result in gales again over the northern California/southern Oregon coastal waters late Thursday night into Friday night. At this time, it appears winds will remain just below gale over the offshore waters. Will populate wind grids using the 12z GFS 10m winds through the period.
.Seas...The 18z sea state analysis indicated seas were mostly within a foot of the latest wavewatch iii and ECMWF wam, although based on a recent altimeter pass the seas over the far east portion of the northern California offshore waters were about 2 to 3 feet too low. Went with a 16 ft Max for the analysis. For the wave grids, will use the wavewatch iii, however will add a few feet tonight over the northern California waters.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... .pzz815...inner waters from Florence or to point St. George... gale today into tonight.
.Pz6 California waters... .pzz820...inner waters from point St. George to Point Arena... gale today into tonight.
.Forecaster kosier. Ocean prediction center.