Marine Weather for HS 102


marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 759 am PDT Sat Apr 21 2018

.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.

The most recent satellite pictures show a quiet pattern across the eastern Pacific, while an altimeter pass from 10z indicates seas to 13 ft over the northern Washington waters. We should start receiving ascat data around 17z. At this time I don't plan on making any changes to the current grids or associated text forecasts. ----------------------------------------------------------------- Previous discussion...

00z global models in good agreement through much of the forecast period, with some differences noted in the track of a developing weak cutoff low near the northern pz6 and SW pz5 waters late Wed into Wed night. For the wind grids, will lean towards the 00z GFS through Tue night, and then to address differences in cutoff low positions on day 5 will transition to the 00z UKMET Wed and Wed night. However by that time all models show a weak pattern with winds well below gale force.

Models remain in good agreement with the timing and strength of a cold front currently passing just E of the pz5 waters and into the northern pz6 waters as per 06z NCEP surface analysis. Models show winds to 30 kt in the westerly flow behind the front lasting into early Sat. 00z NAM and ECMWF hinting at potential for some gales in the westerly flow behind the front, but keep them north of the area. With no ascat available, cannot confirm, but with the associated low pressure to the N lifting N and inland for start of forecast will keep them north of the area.

High pressure ridge builds strongly across the northwest waters today (sat) and tonight, as a coastal trough develops along California and northern Oregon. No significant changes in the models as they do hint at a period of gales in the coastal waters tonight, and again late sun into Sun night. Question is whether these gales extend out far enough to the west to affect the adjacent offshore waters. Again, the best chance for any gales in the offshore waters is tonight, and will continue with some gales in the northeastern portion of pzz820 for tonight, in line with the adjacent coastal offices. For late sun into Sun night, gales look to be confined to the coastal zones and will leave winds to 30 kt for now, as the ridge over the pz5 waters will begin weakening by then, although the coastal trough will remain strong. Confidence in gales for the offshore waters tonight is low, with the best chance for gales during this time frame being the coastal waters. Will boost the 10 meter 00z GFS winds by 10 percent off the northern California coast Sat night to keep gales in the forecast, and again late sun into Sun night.

Ridge slowly weakens sun through Mon night, then rebuilds northwest of the area Tue and Tue night. Meanwhile, coastal trough strengthens somewhat along the Oregon coast, with winds to 25 kt expected. Trough then moves offshore Wed and Wed night, as the aforementioned cutoff low forms W of the pz6 waters and passes near the NW pz6 and SW pz5 waters.

.Seas...Wave guidance within a foot or two of current observations. For the wave grids, will lean towards the 00z enp guidance through the forecast period.

.Extratropical storm surge guidance...N/A.


.Pz5 Washington/Oregon waters... None.

.Pz6 California waters... .pzz820...inner waters from point St. George to Point Arena... gale tonight.


.Forecaster Mills/Bancroft. Ocean prediction center.

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