marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 129 PM PDT Mon Sep 24 2018
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
Strong high pressure remains positioned west of the pz5 waters this afternoon, maintaining an enhanced pressure gradient over the southern pz5 and northern pz6 offshore zones. Gales are likely ongoing off the northern California coast, although the recent ascat passes failed to Sample the region once again. But with the 12z guidance continuing to support offshore gales, we will maintain the warnings for pzz820/815 into tonight with high confidence.
In the medium range, the global models remain in very good agreement into the weekend. The offshore ridge will gradually move northwest and weaken through late week, allowing the gradient to slowly relax over the pz5 waters. Weak low pressure will develop west of the northern pz6 zones Wed/Wed night, and eventually move into the waters by Fri/Fri night with winds 20 kt or less. Stronger northerly winds to 30 kt are expected over the northern pz5 waters Wed night through Thu night as a trough sharpens off the coast of Vancouver Island. Another weak low pressure system will move off the Washington/Oregon coast Fri and slowly pull a trough across the pz5 zones through Sat night. At this time, no additional warnings are necessary for the offshore waters. We will continue to favor the GFS winds given good model continuity.
.Seas...Significant wave heights were analyzed to 15 ft over pzz820 at 18z based on ship reports and earlier Jason-3 altimeter data. Both wave models continue to run slightly low off northern California, so our near term grids will be manually adjusted to reflect our analysis. Otherwise, the 12z wavewatch grids were used for much of this forecast. However, the seas over the southern pz6 waters were manually adjusted late in the period to reduce swell from a distant tropical system with which the GFS is particularly aggressive and further north than the rest of the guidance.
.Extratropical storm surge guidance...No significant positive surge events are expected over the next several days.
.Pz5 Washington/Oregon waters... .pzz815...inner waters from Florence or to point St. George... gale tonight.
.Pz6 California waters... .pzz820...inner waters from point St. George to Point Arena... gale today into tonight.
.Forecaster reinhart. Ocean prediction center.