marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 244 am PDT Tue Apr 24 2018
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.
The current 06z surface analysis shows a cold front approaching the pz5 waters from the NW. The front extends SW and becomes nearly stationary W of the southern Oregon and northern pz6 offshore waters while leading into a weak low near 40n 136w which appears on GOES-15 water vapor imagery associated with an upper low which appears nearly statioary. The front then continues S from the low to 30n 140w. Over the offshore waters the ridge has dissipated with the flow mostly northerly on the west side of a coastal low pressure trough. Pressure gradients are relatively weak. No recent ascat imagery is available, and available surface observations in and near the coastal and offshore areas show mostly winds 20 kt or less, in line with 00z model fields.
The 00z models show the aforementioned low on the front gradually sinking S as the frontal boundary dissipates. The strongest winds will be west of this low but winds are likely to increase behind the front over the pz5 waters as it enters the waters today. A second low center will form in the low pressure trough central or northern California and move offshore by early Wed and is likely associated with an upper shortwave rotating around the south and then east sides of the upper low. The weak low center is expected to remain nearly stationary just W of the waters late Wed through Thu night before tracking NE across the region. A NW flow will gradually spread over the region toward the end of the period as the upper low and associated weak surface low(s) move inland. The 00z global models are in pretty good agreement, especially the 00z GFS and ECMWF. The 00z global Gem moves the surface reflection of the upper low out too quickly and the 00z UKMET is in improved agreement with other guidance through Fri night, but is weaker with winds in the northern waters on day 5. The GFS builds the high too far south Sat and Sat night relative to other models leading to more widespread strong northerly winds and possible gales in the far NE, and appears the outlier. Therefore populated winds with the representative 00z GFS 10 meter winds through Thu and then early Thu night transitioned to 00z ECMWF for the remainder of the period.
Seas...both the 00z enp ww3 and 00z ECMWF wam appear to forecast reasonably well during much of the remainder of the week, depending on their associated wind forecast. I will populate the wave grids using the corresponding model to match the winds, with notably the ECMWF preferred especially late in the period.
.Extratropical storm surge guidance...N/A.
.Pz5 Washington/Oregon waters... None.
.Pz6 California waters... None.
.Forecaster Bancroft. Ocean prediction center.