marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 727 am PDT sun Sep 25 2016
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
At 12z a warm front was just NE of the nrn WA waters W/a high pres ridge over the rest of the WA/OR/CA offshore zones. A 1013 mb low was located just off the srn CA coast W/a trough extending NW from the low along the CA coast into the srn or coast. W/the 06z GFS/NAM being in good agreement W/the 00z model package see no reason to make changes to the ongoing forecast in place for this intermediate update.
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Summary...for the most part the 00z global models remain in very good agreement over the eastern North Pacific Ocean during the next 5 days. An upper level high pressure ridge currently centered along 125w or so will slowly weaken and shift inland during the next 24-48 hours as an upper level trough slides east over the Gulf of Alaska. The trough will weaken as it slides east over western Canada on Mon. A weak ridge will develop in the wake of this trough over the far eastern North Pacific Tue as upper level low organizes over the eastern and central Gulf of Alaska. This system will move east and southeast toward the offshore waters Wed...and begin to cross the waters Thu. At the surface we still expect cold fronts to impact especially Washington and Oregon waters Mon and Mon night...and again Wed night into Thu night...as noted in previous opc forecasts.
Models and headlines...as the 00z global models remain well clustered and quite consistent we will rely on the 00z GFS 10m winds for the early morning forecast package. This will result in only minor changes from the past few opc forecasts...with no headlines currently expected over the offshore waters during the next 3 to 5 days. Gales are currently occurring north of the waters near Vancouver Island per the latest observations and a-scat overpasses. Gales are still forecast to remain north of the offshore waters during the next 24 to 48 hours as low pres areas track north and northeast and pass west and north of the offshore waters. There is a chance for gales off the northern California and southern Oregon coasts Tue afternoon into Wed as the pressure gradient tightens between high pressure west of the waters and lower pressures near the coast and inland over The Rockies. At this time...it appears as if the best chance for these gales will be over the coastal waters with chances remaining too low to add to the offshore forecast for this package. Overall...the confidence levels in the early morning forecast are above average as the 00z models are in very good agreement through Thu night.
.Seas...The 00z ECMWF wam wave model output appears to be a little better than the 00z wave watch iii model output based on the latest observations and altimeter data over the eastern North Pacific early this morning. Maximum sea heights near Vancouver Island are near 18 ft or so...with 10 ft seas occurring off the central California coast per the 06z rp1 sea state analysis... with these Max heights better reflected by the 00z wam guidance. We will therefore remain closer to the 00z wam wave guidance throughout the next forecast package...with the 00z wave watch iii model guidance potentially over forecasting sea heights later Tue into Wed off the southern Oregon and northern California coasts. Some manual edits will be made so that opc wave heights forecast fit with nearby coastal and TAFB forecasts through the next forecast package.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... None.
.Pz6 California waters... None.
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.Forecaster Holley/Mills. Ocean prediction center.