marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 826 PM PDT sun Aug 19 2018
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
High pressure remains to the W of the nrn and central areas of the offshore waters this evening while a trough was near the N CA coast. Another trof remains along Vancouver Island. Will diminish winds slightly to 25 kt over the nrn WA waters tonight and also for Mon for the trof near the N CA coast over the inner N CA offshore waters due to the pressure gradient now over this region supporting winds to 25 kt and it seems more likely to be the case for Mon. Otherwise will make few adjustments to prior gfe grids which look reasonable.
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High pressure still to the west of the region is on track to slowly shift south while weakening in the short term and then re- develop to the west and strengthen as it extends its ridge into the northern waters. Latest goes16 rgb geocolor satellite images show mostly few warm clouds across the region and also depicts cyclonic circulation southeast of the central Aleutian Islands. Latest NCEP weather map has high pressure to the west of the region with one center 1032 mb 240 nm west of the North Washington outer offshore waters. Inland trough across California stretches from low pressure 1004 mb over Southern California. Another trough is across the Vancouver Island. Pressure gradient is fairly relaxed across the region and maximum winds are 25 kt over the far northern waters.
At 500 mb, area of high pressure extends across the central California state while a weak trough with some energy covers the pz5 zones. In the short term, a ridge to the west of the region will force the energy over the northern waters to move east inland as it moves east. The ridge will persist to the west of the region through most of the forecast period and the resultant surface features will remain weak.
The models GFS/ukmethr/ecmwfhr/CMC/NAM have initialized well the latest synoptic surface observations. The models are also in a good agreement on keeping high pressure to the west of the region. There are small variations in the extended period mainly on the strength of the inland trough along California but models agree on keeping winds below gale force threshold through the forecast period. Will continue with GFS for winds.
.Seas...They range between 6 and 9 ft over the central and northern waters with a peak at 10 ft over the Washington waters and they range between 4 and 6 ft over the southern waters. Jason iii pass about 0827z missed the area with larger seas showed relatively large seas over the northern waters. Nww3 and ecmwfwave models fit well the observed seas pattern over the offshore waters and also over the high seas. Both wave models have quite consistent in previous runs and they continue to agree well in the short term on maintaining a similar seas pattern with peaks at 11 ft. Will just stay with enp for the seas grids.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... None.
.Pz6 California waters... None.
.Forecaster Rowland/musonda. Ocean prediction center.