HS 102

marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 545 am PST Wed 11 Nov 2009

.Forecast discussion: major features/winds/seas/significant .Weather for the North Pacific N of 30n and E of 150w.

Mrng update...a low pres area currently over the E Gulf of AK will slide se towards the WA wtrs into tngt. The low will weaken as it mvs inlnd nr SW WA Thu. A strong cdfnt will approach the pz5 zones Thu ngt...then cross the region Fri. Anotr strong fnt approaches Sat and passes over the area later Sat into sun. High pres will build W of the pz6 zones tdy thru late week resulting in increased wnds over the S/cntrl pz6 wtrs. Still a slight chance for gales W of pt Conception late Thu into Fri. Not enuf confdc yet to add a wrng.

06z runs of GFS/NAM compare well with the prev fcst with no major changes planned. The GFS shows a strong low passing NE thru the WA wtrs sun with storm frc wnds. This is quite diff from the prev fcst and otr mdl solns so will ignore it for now.

Seas...06z run of ww3 is within 1-2 ft of ltst sfc obs over the offshr. Gdnc is running about 2-4 ft too high over the cstl wtrs N of pt Arena to Cape Flattery. Do not anticipate major changes in seas from prev fcst.

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Previous discussion

The late eve sfc map...06z prelim opc/NCEP map...shows a weakening cold front ovr nrn socal wtrs with a high pres ridge ovr central cal off wtrs...and a large high ovr the central pac ocean centered nr 41n159w. Low pres is ovr the NE Gulf of AK with low pres trofs extending S...SW and NW from the low. Max sea hts nr 18ft are assoc with the low ovr the NE Gulf of AK per the 06z rp1 opc sea state analysis with sea hts ovr the off wtr ranging from a low of 7 ft ovr se socal to as much as 13 ft ovr wrn oreg wtrs. Sea hts ovr the off wtrs are gnrly within a ft or so of the 00z wave watch iii mdl.

Near term...the 00z mdls are gnrly in good agreement ovr the off wtrs thru Fri. As a result...we will remain close to the 00z GFS mdl for this package thru Fri. The high pres area noted above will slowly build E toward cal off wtrs thru Fri...as the low ovr the NE Gulf of AK tonite moves se and crosses wash wtrs late Wed and Wed nite. The low wl lkly dsipt ovr oreg Thu...with a strong cold front approaching pz5 wtrs from the W and NW late Thu. This front is still expected to cross pz5 wtrs Thu nite into Fri...and nocal wtrs Fri...before wkng and dsiptg ovr central cal wtrs Fri nite. A high pres ridge will build ovr pz5 and nocal wtrs behind this front ltr Fri and Fri nite. Gales still appear most lkly ovr wash wtrs nr the front Thu nite into Fri...with a chance for gales ovr socal and se central cal wtrs lt Thu into Fri. We will cont to monitor this area for psbl gales...as the 00z GFS now appears a little weaker with the fcst pres gradient than the 18z run ovr that region. We will keep Max winds at 30 kt ovr socal and se central cal off wtrs for this package Thu into Fri.

Long term...in comparing the past few runs of the GFS...it appears that the 12z run from Tue was too weak regarding low pres movg into the Gulf of AK Sat. The 00z run is consistent with the 18z run...and has excellent support from the 00z ecwmf which both place a 958mb low pres area nr 55n150w by 12z Sat. Also supporting the GFS and ecwmf is the 00z NAM which places a 948mb low N of the GFS low psn by early Sat. The 00z NOGAPS is also similar. The 00z UKMET and 00z Canadian both appear too weak with this low and too far N...so they will be ignored. The 00z GFS and 00z ECMWF again remain in pretty good agreement thru late Sat and sun ovr the region. We will therefore remain close to these solutions for this package. This will for the most part result in only minor changes from the prev fcst...with gale headlines remaining ovr wash wtrs Sat as the next strong front crosses these wtrs.

Seas...the 00z wave watch iii mdl will for the most part be followed for this package...which will tend to result in only minor changes from the prev fcst. A large...long pd...swell generated by the deep low ovr the Gulf of AK late in the wk and ovr the wknd will reach wash wtrs by sun with sea hts potentially nr 20 ft arriving ovr the NW part of The Wash wtrs late sun... with the higher seas passing just N of the wtrs per the ww3 mdl. Confidence in these higher swells reaching The Wash wtrs is slightly higher than average as GFS and ECMWF solutions are in vry good agreement ovr the wknd ovr most of the NE pac ocean.

.Warnings/forecast confidence...Warnings are preliminary and are subject to change. Any changes will be coordinated through AWIPS 12 planet chat or by telephone.

.Pz5 Washington/Oregon waters... .Cape Flattery to Cape Lookout...gale Thu ngt into Fri...MDT to high confdc. Gale Sat...low to MDT confdc. .Cape Lookout to point St George...None.

.Pz6 California waters... .Pt St George to pt Arena...none. .Pt Arena to pt Conception...None. .Pt Conception to Guadalupe island...None.

.Forecaster banks/Mills. Ocean forecast branch.