Oahu-
300 am HST Thu Nov 26 2009

...High surf warning for north and west facing shores...

Surf along north facing shores will be 15 to 25 feet lowering to 12 
to 18 feet this afternoon.

Surf along west facing shores will be 10 to 20 feet lowering to 7 
to 12 feet this afternoon.

Surf along east facing shores will remain 3 to 5 feet through 
Thursday.

Surf along south facing shores will continue at 1 to 3 feet through 
Thursday.

Outlook through Tuesday Dec 1:
surf is expected to drop below advisory levels Friday morning but a 
new north northwest swell will arrive Saturday...boosting surf back 
to near advisory levels. 

Surf heights are forecast heights of the face or front of waves. The
surf forecast is based on the significant wave height...the average
height of the one third largest waves...in the zone of maximum 
refraction. Some waves may be more than twice as high as the 
significant wave height. Expect to encounter rip currents in or near
any surf zone.

&&

Collaborative nearshore swell and wind forecast for Oahu
NWS/ncddc Honolulu HI
300 PM HST Wed Nov 25 2009

This collaborative forecast will be updated Monday through Friday at
300 PM when pat Caldwell is available. When pat Caldwell is not
available...the latest collaborative forecast will remain posted for 
4 days. 

Forecast  swl  dmnt dmnt  h    h     hgt          wind   wind   spd
date      hgt  dir  pd    1/3  1/10  tend   prob  spd    dir    tend

1 PM       11  NNW   15    22    28  up           17-21   ENE   up  
11/25       6  E      7     2     4  up  
            2  S     13     2     4  down

Thu         9  NNW   14    16    22  down   high  22-27   ENE   up  
11/26       5  NNE   10     6     8  up     Med 
            9  ENE    8     6     8  up     Med 

Fri         7  NNW   13    12    14  down   Med   22-27   ENE   same
11/27       5  NNE   10     6     8  down   low 
            9  ENE    8     6     8  same   Med 

Sat         7  NNW   16    12    16  up     Med   17-21   ENE   down
11/28       9  ENE    8     6     8  down   low 

Sun         6  NNW   14    10    12  down   Med   17-21   ENE   same
11/29       7  ENE    8     4     6  down   low 

Mon         7  NNW   15    12    16  up     low   17-21   ENE   same
11/30       7  ENE    8     4     6  same   low 
            2  SSW   15     2     4  up     low 

Legend:
swl hgt    open ocean swell height measured from trough to crest
           in feet located 20 nautical miles offshore
dmnt dir   dominant direction typically +/-10 degrees in 16 Compass
           points
dmnt pd    dominant period in seconds
h1/3       significant wave height in the surf zone
h1/10      average height of the highest one-tenth waves in the surf
           zone
hgt tend   height tendency of swell (valid values: up/down/same)
prob       probability of occurrence (valid values: high/Med/low)
wind spd   open water wind speed measured in knots located
           20 nautical miles offshore
wind dir   wind direction in 16 Compass points
spd tend   wind speed tendency (valid values: up/down/same)

Surf heights will vary between different beaches and at the same 
beach at different break areas.

Discussion:
summary...
active late fall pattern for North Shore surf.

Detailed...
mid-Wednesday on northern shores has extra-large heights...meaning 
significant breakers on outer reefs...from 315-330 degrees with 
14-17 second periods. This episode is expected to remain high on 
Thursday.

After an extended period with a blocking ridge near the dateline 
during mid November...giving below average surf locally...the jet 
stream has shifted southward since last weekend over the northwest 
and central North Pacific...bringing the wave sources closer and 
making the local surf higher. Surface low pressure systems are 
spaced a few days apart...making overlapping episodes locally.

A low pressure system...or extratropical cyclone...formed east of 
the Kuril Islands last Saturday. Gales to severe gales in the 
315-330 degree band were allowed to reach fully developed seas due 
to the captured fetch...meaning the growing seas traveling at about 
the same speed as the advancing low pressure center. The head of the 
fetch reached to within 1000 nm of Hawaii by early Monday. 

Surf from this source rose abruptly Wednesday morning to extra-large 
heights. Buoy 51001 was not available after 10 PM Tuesday...though 
the backup buoy 51101 kept measuring. It showed a peak to the 
episode around 7 am...equating to a local peak for around 3-5 PM 
Wednesday. 

With the long fetch of the source centered on 320 degrees...this 
episode should hold for a few more days as the surf heights slowly 
fade...dropping below the high level on Friday morning.

The extratropical cyclone associated with this episode raced NE to 
the Gulf of Alaska on Tuesday...with too short a duration for surf 
beyond moderate levels. On Friday...the directional swath should be 
wide...from 315-360 degrees...centered on about 345 degrees. A 
larger episode will override this event on Saturday.

An extratropical cyclone tracked from Kamchatka starting early 
Tuesday to east of the dateline just south of the Aleutians on 
Wednesday. Gales to severe gales...with a small area of storm-force 
winds...filled a fetch in the 320-330 degree band...with the head of 
the fetch about 1800 nm away mid Wednesday. Models show the system 
moving east out of the Hawaii swell window on Thursday.

Surf should build on Saturday morning...reaching marginally high 
levels Saturday afternoon...and favoring moderate levels on 
Sunday...all from 315-340 degrees...with some of the more northward 
component a result of angular spreading from swell trains missing 
Hawaii to the immediate NE.

Models show a new low pressure gaining gale status near the dateline 
late Thursday...tracking south of the Aleutians well north of Hawaii 
with storm-force to hurricane force winds on Saturday. This could 
give way to another high episode on Monday from 320-345 
degrees.

Strong to near gale winds on the backside of a front about 400 to 
800 nm NNE of Hawaii late Tuesday into Wednesday could make for a 
short-period episode from 010-030 degrees...building Thursday 
afternoon...peaking early Friday...and dropping quickly early 
Saturday.

Mid-Wednesday on windward shores has small breakers under moderate 
to fresh breezes. Models show trades increasing to fresh to strong 
levels on Thursday into Friday...with rough surf building to 
marginally high levels...especially for more northerly exposures for 
the short-period episode mentioned above. Fresh trades over the 
weekend should keep moderate breakers into early next week.

Mid-Wednesday on Southern Shores has small...inconsistent southern 
hemisphere energy...as validated by the kilo nalu buoy. This episode 
should fade away later today. Refracting windswell from the east 
could make for small breakers through the period for select 
locations.

A fast-moving...compact...storm-force system to the se of New 
Zealand last Saturday into Sunday could make for a small episode 
locally starting late Sunday into Monday from 180-200 degrees.

Into the long range...more gales are expected se of New Zealand over 
the next 48 hours...making for another round of small...long-period 
surf locally later next week.

In the northern hemisphere...models keep an active jet stream from 
the Kurils to the dateline...with troughs dipping toward Hawaii... 
making for both remote and nearby sources. This should keep 
overlapping episodes through next week with most episodes topping 
out near the high mark though potential for extra-large heights are 
reasonable considering the proximity of the track to Hawaii. With 
the closer track...winds likely to vary greatly from day to day... 
from any point on the Compass.

Long range forecasts are subject to low confidence. 

This collaborative forecast will resume on Friday...November 27.

This forecast was produced through the collaborative efforts of
NWS and ncddc. Please send suggestions to W-hfo.Webmaster@noaa.Gov
or call the warning coordination meteorologist at 808-973-5275.

Additional resources:
see /in lowercase/  http://www.Prh.NOAA.Gov/hnl/pages/marine.Php