AGPN40 KWNM 270941
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
241 AM PDT Sun May 27 2018

.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.

The 06Z NCEP surface analysis indicated warm front has lifted N
of the waters while a cold front approaches from the NW. GOES15
satellite loop indicates wave forming on the front W of the
Washington waters. High pressure centered near 36N 139W extends a
ridge NE to the Oregon waters. ASCAT-B pass from around 0550Z
continues to indicate several areas of 25 KT northerly winds from
the inner southern California waters N to the southern Oregon
coastal waters. This matches up well with model forecast fields,
in particular close to 00Z GFS.

The 00Z models continue to be in very good agreement throughout
with some differences appearing after Wed mainly affecting the
northern waters. An inverted trough will strengthen along the
northern and central California coast over the next three days,
while the high pressure area W of the California offshore waters
moves slowly E before weakening Monday and then reforming W of
the Oregon and northern California waters later Monday and
Monday night. Initially expect gales to be confined to the
northern California and far southern Oregon coastal waters from
Sun night into Tueday before expanding into adjacent offshore
waters off northern and central California Tue night through Wed
and may extend into early Thu in adjacent central California
coastal waters. Will use the 10 meter winds of the 00Z GFS
through Tue and then as the gradient increases further will
transition to a 50/50 blend of 00Z GFS first sigma layer and 10
meter winds from 00Z Wed to 00Z Thu. This will result in few
changes to existing warning headlines. Looking ahead to the end
of the week, the 00Z models offer divergent solutions regarding
low pressure moving over a broad upper ridge W of the offshore
waters and toward the northern waters Wed night into Thu night.
00Z ECMWF made sudden change dissipating the low and showing more
of a ridge while 00Z GFS trended toward the old 26/12Z ECMWF on
which the previous forecast was based, and which the new WPC
medium range guidance is sticking with. Therefore retained the
previous forecast grids beyond Wed. Effect will be to weaken the
gradient off California with gales ending by early Thu.

.SEAS...The 06Z sea state analysis indicated that observed seas
matched up closest to the 00Z ECMWF WAM which is used for the
wave grids in the first period. After today and through Wed will
continue to use a 50/50 blend of Wavewatch/ECMWF WAM, then will
transition to the previous grids based on the 26/12Z ECMWF WAM
from Wed night through the remainder of period.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
None.

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
Gale Possible Tuesday into Wednesday.
.PZZ825...Inner Waters from Point Arena to Pigeon Point...
Gale Possible Tuesday into Wednesday.
.PZZ830...Inner Waters from Pigeon Point to Point Piedras Blancas...
Gale Possible Tuesday night into Wednesday.

$$

.Forecaster Bancroft. Ocean Prediction Center.