marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 709 PM PST Tue Jan 22 2019
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
The 00z surface analysis indicates low pressure moving east just to the north of the waters, with a cold front moving into the northern waters. This will bring some gale force winds to the northern waters tonight. These will diminish by 09z Wednesday.
The current model guidance is very good through the forecast period, with the GFS and CMC having come into agreement with the more consistent ECMWF and UKMET. We will populate the grids with the ECMWF, boosting the winds through 12z Wednesday to keep the gale force winds expected with the low pressure.
We will use the wam for the seas throughout the forecast as it has also been consistent for the last several days. Fortunately, the wave models have continued with good agreement and have initialized well.
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High pressure will continue to the west of the region as low pressure moves east to the north of the region pulling a cold front across the northern waters in the short term. High pressure will move north and allow inland thermal trough to slightly strengthen along California coast and that will elevate winds over the eastern portion of the central California waters in the extended period. Latest NCEP weather map has a trough along the California coast and high pressure 1034 mb is just west of the central California waters while low pressure near Vancouver Island has a front stretching south and reaches the northeastern Washington waters as a cold front. Low pressure 1005 mb about 480 nm west of the Washington waters extends a warm front east into the Washington waters. Pressure gradient is tight over the Washington and northern portion of Oregon waters while pressure gradient is fairly relaxed over the region elsewhere.
A high pressure ridge still lies to the west of the region in the upper levels and models suggest that in the short term, as it expands northwest, it will allow some energy to penetrate east and pass over the northern waters. The ridge will then persist into the extended period. The resultant surface synoptic features will be persistent high press just west of the region. Pressure gradient should therefore remain relaxed most of the forecast period and winds will remain below gale force. As such will seek model that will keep winds below gale force threshold over most of the region after the frontal passage in the short term over the northern waters.
Global models have initialized well the high pressure to the west of the region but have small differences on the actual position of the fronts over the northern waters. Models also differ slightly on the areal extent of the gale force winds over the northern waters. A comparison between GFS and ecmwfhr show that ecmwfhr winds are 5 kt weaker over the northern waters than GFS initially. In the short term both models push low pressure east just north of the waters but ecmwfhr low is 2 mb deeper than GFS and again GFS has winds 5 kt stronger than ecmwfhr. Will favor deeper low and slightly stronger winds and so for winds will stay with GFS.
.Seas...They range between 6 and 11 ft over the northern and southern waters while they range between 4 and 6 ft over the northern California and southeastern Oregon waters. Nww3 fits well the observed seas pattern and has been quite consistent in previous runs. Ecmwfwave model also fits well the observed seas pattern and both wave models agree in the short term on maintaining smaller seas over the central region. In the extended period, though the wave models have a general agreement on building seas over the norther waters, they differ slightly on the peak values within 2 ft. Otherwise, the models agree well over the southern waters where seas will remain smaller. Since the differences a small, will just use nww3 in the short term and part of the extended period then switch to ecmwfwave toward the end of forecast period.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... None.
.Pz6 California waters... None.
.Forecaster Sommerville/musonda. Ocean prediction center.