marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 603 am PST Tue Nov 20 2018
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
A cold front currently approaching the pz5 and northern pz6 waters will move into the area today while low pressure forms along the front. The low will then move north across the pz5 waters tonight and should be strong enough to produce some minimal gale conditions. Another cold front will then approach the pz5 waters Wednesday and move into the area early Thursday. Gale conditions are still expected ahead of the front across the pz5 and northern pz6 waters Thursday and Thursday night. Yet another cold front will then move into the pz5 waters Saturday night. Farther south, mainly light winds are expected across the southern pz6 waters today into Thursday night. For wind grids will continue to use the current grids throughout the forecast period. Current warnings look reasonable and few changes should be needed on the next offshore waters forecast.
For wave height grids will also continue to use the current grids throughout the forecast period.
.Extratropical storm surge guidance...The 06z estofs and etss guidance show positive surge values to 1 ft or so extending along the Washington and northern Oregon coast on Thu. With the models coming into better agreement on the strong frontal system described above, these values appear reasonable based on our latest wind forecast.
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A weak, occluded low pressure system was analyzed over the Southern California waters near 31n 122w at 06 UTC. An earlier ascat pass around 0445 UTC indicated southeast winds to 20 kt associated with this system. Elsewhere, southerly winds are strengthening over the pz5 waters ahead of a cold front west of the area along 132w. A frontal wave will develop later today as the front nears the outer waters, and this low will track north across the outer pz5 zones while gradually deepening tonight. Although the 00z guidance offered mixed signals regarding the potential for gales, the GFS has consistently shown them for several cycles, including the 00z run. Therefore, we will maintain a brief Gale Warning overnight for our outer Washington waters as the low passes over the region.
The 00z models converged on a slightly faster solution regarding the strong cold front crossing the northern waters on Thu. In fact, all the global models now keep the occluded parent low well north of the offshore zones as the front races across the pz5 and northern pz6 waters. Beginning Thu, we transitioned our wind grids from the 00z GFS to the 00z ECMWF. The ECMWF/UKMET/NAM all bring the front farther south than the GFS into the northern California waters. The ECMWF has been more consistent in recent cycles and appears to match up better with wpc guidance as well. Ultimately, this maintains gale warnings for all our zones north of Point Arena, CA on Thu.
The front will lift back north as a warm front Thu night ahead of a low pressure system expected to track across the southern pz5 or northern pz6 zones early Fri. Recent model trends suggest gales are possible south of the low track, but for now the 30 kt ECMWF solution serves as a good compromise between the stronger GFS/weaker UKMET solutions. A low pressure trough will cross the pz5 waters later Fri, but the 00z ECMWF/GFS/UKMET all keep winds below gale force at this time. Finally, another cold front will approach the northern waters this weekend with the potential for gales ahead of the front on Sat. Given the uncertainty at day five, we will confine gales north of the forecast waters until confidence increases.
.Seas...Wave heights are beginning to build over the northwest pz5 zones ahead of the approaching cold front. At 06z, seas were 6-7 ft in this region and generally less than 6 ft elsewhere. In the near term, the 00z wavewatch worked well with some minor edits along our coordination borders. On Thu, we transitioned to the 00z wam since the ECMWF winds were preferred through the medium range period.
.Pz5 Washington/Oregon waters... .pzz800...inner waters from Cape Flattery to Cape Shoalwater... gale possible Thursday. .Pzz900...Outer waters from Cape Flattery to Cape Shoalwater... gale tonight. Gale possible Thursday. .Pzz805...Inner waters from Cape Shoalwater to Cape Lookout... gale possible Thursday. .Pzz905...Outer waters from Cape Shoalwater to Cape Lookout... gale tonight. Gale possible Thursday. .Pzz810...Inner waters from Cape Lookout to Florence or... gale possible Thursday. .Pzz910...Outer waters from Cape Lookout to Florence or... gale possible Thursday. .Pzz815...Inner waters from Florence or to point St. George... gale possible Thursday. .Pzz915...Outer waters from Florence or to point St. George... gale possible Thursday.
.Pz6 California waters... .pzz820...inner waters from point St. George to Point Arena... gale possible Thursday. .Pzz920...Outer waters from point St. George to Point Arena... gale possible Thursday.
.Forecaster nolt/reinhart. Ocean prediction center.