HS 102

marine weather discussion for N Pacific Ocean NWS ocean prediction center Washington DC 715 PM PDT Wed 22 may 2013

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

Update...

Do not plan any significant adjustments to this package. The 18z GFS and NAM are consistent with the 12z guidance esp for the short range portion of the forecast. Will continue with gales for the cntrl and srn CA waters overnight into Thu with the gradient between the inland coastal trof and high pres W of the waters.

For the long range portion of the forecast...the latest GFS shows gales over the srn CA waters developing later and persisting longer than in the previous run. Gales are now forecast to develop Mon rather than late sun...and persist through the end of the forecast period rather than into early Mon. Given that this is at the tail end of the forecast...will wait to check all available 00z guidance before making any changes.

The ww3 initialized well compared to the 00z obs...so will generally follow its output.

Previous discussion follows ----------------------------------------------

At 22/1800z low pres 1010 mb 90 nm N of the region with gale force winds has a trof that xtnds NW along the Canada coast while another trof stretches se then curves SW into the nrn wtrs. Inland low pres 998 mb ovr AZ/NV xtnds a trof acrs CA state. Hgh pres 1036 mb cntred 500 nm due W of the oreg/cal wtrs xtnds a ridge into the Gulf of AK and has another ridge into the cntrl and srn wtrs. A tight pres grdnt exits btwn the hgh and the trof along CA. Gale force winds are confined to the ern edge of the srn wtrs nr the inland trof. The latst asct pass at 1700z only covered the far srn parts of the region. The previous pass at 06z had gale force winds NW of the nrn wtrs. The glbl mdls are in gud agrmnt. The hgh pres to the W of the region will keep moving S as it weakens. The inland low pres trof will persist acrs CA but the pres grdnt will slacken as the hgh moves S. Gale force winds wil be confined to the ern edge of the cntrl wtrs thru Thu then will diminish to below gale force thru most of the preiod. The hgh pres will strengthen hwn it gets S and become nrly stnry just before end of fcst prd. The oinland low pres trof will deepen and that may force a tight pres grdnt ovr the srn wtrs to hve winds elevated to gale force. Will stay with GFS for this pckge.

Seas...the hgst seas are ovr the nrn wtrs peaking at 19 ft with another peak of 17 ft ovr the ern edge of the cntrl wtrs. The nww3 multi grid fits well with the curr seas pattern and seem quite reasonable with the fcst.

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...none. .Pt Arena to pt Conception...Gale overnight into Thu...hi condnc. .pt Conception to Guadalupe island...gale overnight into Thu..hi condnc. Gale sun...low confdc.

$$

.Forecaster Bell/musonda. Ocean prediction center.