HS 102

marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 724 PM PDT Sat may 18 2013

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

Will not make any wholesale changes this update. However...am concerned that gales may need to be reintroduced to the pz05 wtrs Tue into Wed. Though there is now about a 150 nm spread in mdl solutions W/the low track over the wtrs...W/the GFS furthest N and UKMET furthest S...all the glbl mdls depict at least a brief period of gales in the nwrly flow on the back side of the low. The GFS is the most aggressive here. Will take a hard look at the 00z gdnc to determine if we need to bring gales back into the forecast with the next update.

----------------------------------------------------------------- Previous discussion...

The ltst GOES vis imgry indc a wkng cdfnt acrs the nrn pz6 and srn pz5 wtrs attm...and high pres W of the c cal wtrs. The WV imgry indc a slowly amplifying upr rdg nr 130w...and drifting E. The 12z guid indc the h5 hgts wl rise ovr the cal coast tngt into MN as the upr rdg moves E...enhancing the thrml trof. Gales are xpctd to begin sun aftn in the strengthening pres grad nr pt Arena...altho mdls are still mrgnl and the GFS has been staying on the cusp of gl frc. Plan on still carrying gales...tho confdc is low to MDT with them.

12z GFS still cont to be outlier with low movg into the ofshr wtrs Mon ngt and Tue...as it takes the low thru the pz5 wtrs and incrs the wnds to gl frc ovr pz5. The rest of the 12z guid favors a track that keeps the gales W of the area...SW of the GFS track. The upr energy indc the assoc shrtwv FM SW wl get picked up by upr trof...tho aside FM GFS rest of guid digs the trof more S. Attm preferring the 12z ECMWF soln on Tue...as confdc with gales is vry low. After cd surge FM shrtwv...mxg wl be enhanced by destabilized environ...and wnds xpctd to incrs to gl frc off cal coast again...with low to MDT confdc due to the rng and again mrgnl nature as depicted by mdls. Wl hav gales ovr the nrn and c cal wtrs late Tue and Wed...and expand into the srn cal wtrs r pt Conception Wed as sfc rdg axis drifts S. Mdls also indc a cd low movg off the nrn coast Wed and Thu...incrsg the wnds ovr the N ptn in the stg grad btwn the high and the new low. ECMWF is an outlier taking it to the S faster than the rest of guid. Attm preferring the UKMET/GFS compromise ovr the N pttn for Wed and Thu.

Seas...staying close to 12z mww3 soln...however switching to 12z ECMWF wave Tue into Wed in conjuction with preferred wx mdl soln...then back to mww3 Wed and Thu as ECMWF bcms outlier. Also...boosting seas late Tue into Wed with gales alng cal coast...as guid seems slow to build.

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...none. .Cape Lookout to Pt St George...None.

.Pz6 California waters... .Pt St George to pt Arena...gale sun into Mon...low to MDT confdc. Gale Tue...low to MDT confdc. .Pt Arena to pt Conception...Gale sun and sun ngt...low to MDT confdc. Gale Tue and Wed...MDT confdc. .Pt Conception to Guadalupe island...Gale Wed into Thu...MDT confdc. $$

.Forecaster Lee/Kells. Ocean prediction center.