marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 818 PM PDT Tue Aug 22 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
Pressure gradient is very relaxed and will persist through the forecast period keeping winds below gale force and seas will only peak at 12 ft over the central waters. Satellite images show mostly cloudy skies across the region with cyclonic circulation depicted in the Gulf of Alaska. Winds range between 10 and 20 kt over the central region and between 5 and 15 kt over the southern and northern waters. At 00z, NCEP weather map has broad high pressure over central Pacific with one secondary center 1025 mb near 35n144w that extends a ridge into the north and southern waters while inland low pressure over Nevada and Arizona border area stretches a trough northwest across California into the central waters. Pressure gradient is well relaxed across the region. Models GFS/CMC/ecmwfhr/ukmethr/NAM have initialized well these few synoptic features and they show good agreement on keeping high pressure to the west of the region while inland trough will persist over California. Will not make any major changes to the current forecast and will stay with GFS.
Seas range between 3 and 6 ft across the region with a peak at 7 ft over the far northwest waters. Wave models nww3 and ecmwfwave fit well the observed seas pattern. The wave models are also in good agreement on keeping seas small but build to 12 ft over the central waters. Will not deviate from previous model choice and so will stay with nww3.
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The 18z surface analysis indicated a weak cold front just to the northwest of the Washington offshore waters and extending southwest. Weak low pressure was just west of the Southern California waters. Several ascat passes from 1721z and 1805z with coverage over all but the central California waters indicated winds 15 kt or less over the entire area.
The 12z models continue to be in very good agreement during the forecast period. The cold front mentioned above will move across the Washington and Oregon waters tonight and Wednesday, then into the northern and central California waters Wednesday night and Thursday before dissipating Thursday night. Winds will remain well below gale with this front. Otherwise, the coastal trough will strengthen later Thursday into Friday night before weakening over the weekend. The models, especially the GFS still indicate a brief period of gales over the far southern Oregon waters and northern California waters Friday afternoon and evening but should drop below gale by late Friday night as trough weakens. A high pressure ridge will rebuild across the Washington, Oregon and northern California Wednesday night and Thursday, and persist through the weekend. Will continue to use the GFS 10m winds to populate winds grids through the entire forecast period.
.Seas...The 18z sea state analysis indicated that observed seas matched up very well with the wavewatch iii forecast values, and plan on going close to the wavewatch iii to populate the wave grids.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... None.
.Pz6 California waters... None.
.Forecaster musonda/kosier. Ocean prediction center.