HS 102

marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 829 PM PDT Tue 21 may 2013

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

Stg high pres to the W of the WA/OR offshr areas wl gradually wkn as it shifts swd thru Wed ngt...then be W of the nrn and cntrl CA wtrs late Fri into Sat. MDT to stg nwly flw prevails acrs much of the offshr wtrs with gales ovr the WA wtrs...and ovr the cntrl and srn CA wtrs. Mdls look smlr with timing the ending of gales ovr the WA wtrs towards mrng and contg ovr the cntrl and srn CA wtrs FM ovngt thru Wed ngt. Do not see much change needed FM prev fcst...and adjstd seas somewhat higher ovngt into Wed ovr the gales areas.

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At 21/1800z inland low pres 1001 mb ovr wash state has a clf frnt stretchng SW into nrn CA and then continues as a trof acrs the cntrl cal wtrs. Another low pres 1009 mb ovr the Canada coast has trofs xndg se and NW alog the coast. Hgh pres 1042 mb about 540 nm W of the nrn wtrs has a ridge xtndg se with its ridge axis passing 300 nm W of the srn wtrs. The pres grdnt is fairly tight ovr the NW parts and ovr the ern edge of the cntrl region. The 18z synop obs hv Max winds reaching 30 kt ovr the ern edge of the cntl wtrs and also ovr the nrn parts of The Wash wtrs. The latst asct pass had some gale force winds ovr the nrn wtrs.

Models...the glb mdls hv initialized well and are in agrmnt on most of the features. Just mnr diffs in the xtdnd prd on the cntrl value of the hgh pres...only NOGAPS seems weak and also the ridging is just out of phase in the Gulf of AK. Otherwise all the glb mdls agree ovr the region. Will stay with GFS.

Short term...thru Thu night...the low pres ovr the Canada coast will mv E inland and sispt while the hgh pres will mv se as it weakens. The pres grdnt will become relaxed and allow winds to diminsh to below gale force ovr the nrn wtrs but the combined effecst fo the inland trof and the hgh pres will still mainatain a tight pres grdnt ovr the ern parts of the cntrl wtrs and that will allow gale force winds to persist there thru Wed night.

Extended period...Fri thru sun...the hgh pres will continue to to weakene and that will relax the pres grdnt farther ovr the region and force the winsd to diminish to below gale force and will remain that way thru the xtdd prd.

Seas...the seas are hgst reachng 18 ft ovr the nrn wtrs. The nww3 multigrid WV mdl fits well with the obs and it appears reasonable with the curr fcst. The ecmwfwave mdl is quite close to the muti grid WV mdl and sip will stay with the nww3 multi grid. The seas will reamin elevated to 18 ft peaks but will start to susbside in the xtdd prd.

Extratropical storm surge guidance...N/A.

.Warnings/forecast confidence...Preliminary. Any changes will be coordinated through AWIPS 12 planet chat or by telephone:

.Pz5 Washington/Oregon waters... .Cape Flattery to Cape Lookout...gale tonight...hi confdnc. .Cape Lookout to Pt St George...None.

.Pz6 California waters... .Pt St George to pt Arena...none. .Pt Arena to pt Conception...Gale tonight into Wed...hi confdnc. .Pt Conception to Guadalupe island...Gale tonight into Wed...hi confdnc. Gale Thu...MDT confdnc

$$

.Forecaster Rowland/musonda. Ocean prediction center.