marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 808 am PDT Tue Sep 19 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
Based on overnight ascat overpasses and buoy/ship data, intend to re-populate the first 24-36 hours of the forecast with the 00z ECMWF winds, while running a local smart tool that increases boundary layer winds where the guidance is notoriously too low (in winds in excess of 20-25 kt). This will yield little change in timing of the expected gales late tonight over outer zones 905 and 910, but it will trim back areal coverage significantly. Confidence remains only average, but will continue to opt on the side of forecast consistency to ensure minimal gales remain in the upcoming forecast.
Otherwise, based on recent lightning data, thunderstorms have moved far enough east and are now only affecting the coastal waters with attendant low pressure trough generally east of 125w. That being said, apparently NAM guidance is whiffing again on the next possibility of convection; as the upper low and trough dig sharply from the Gulf of Alaska overnight into Wed, will need to add mention of thunderstorms across most of our northern zones.
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The latest surface analysis indicates that low pressure just north of the pz5 waters will move inland later tonight and Tuesday. Minimal gales in the northwest flow behind the associated cold front will remain across portions of the pz5 waters tonight. Conditions will then diminish Tuesday. Another low will then move across the northern pz5 waters Tuesday night. Once again some minimal gales are expected in the northwest flow across portions of the pz5 waters behind the associated cold front. These gales will then continue into Wednesday. The northwest flow will then gradually decrease across the pz5 waters through Friday.
Farther south, northwest winds up to 25 knots currently in place off of Point Conception will increase through Tuesday night. By Tuesday night some minimal gales are possible off of Point Conception, but for now will keep the strongest winds at 30 knots across the offshore waters. Northwest winds up to 25 or 30 knots will then remain near Point Conception into Saturday. The latest runs of the GFS and ECMWF look to be in reasonable agreement across the eastern Pacific through Saturday. For wind grids will use the GFS 30m winds with some edits through late Wednesday, then transition to the GFS 10m winds. Current warnings look reasonable and few changes should be needed on the next offshore waters forecast.
For wave height grids will also use the ww3 throughout the forecast period.
Extratropical storm surge guidance: N/A.
.Pz5 Washington/Oregon waters... .pzz905...outer waters from Cape Shoalwater to Cape Lookout... gale tonight into Wednesday. .Pzz910...Outer waters from Cape Lookout to Florence or... gale tonight into Wednesday.
.Pz6 California waters... None.
.Forecaster Collins/nolt. Ocean prediction center.