Pat Caldwell

Outlook
Outlook through Tuesday December 23: a moderate to large northwest swell arriving Thursday afternoon will produce surf just near advisory level along north facing shores into Friday morning. A much larger northwest swell arriving Sunday is expected to produce low end warning level surf Sunday and Monday along north and west facing shores. 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.
Hazards
No high surf advisory or warnings.
Forecast
Surf along north facing shores will be 4 to 6 feet into Thursday morning then rise to 10 to 14 feet late Thursday afternoon. Surf along west facing shores will be 2 to 4 feet into Thursday morning then rise to 6 to 10 feet late Thursday afternoon. Surf along east facing shores will be 2 to 4 feet this afternoon and 3 to 5 feet Thursday. Surf along south facing shores will be 1 to 3 feet this afternoon and 2 to 4 feet Thursday.
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About Collaborative Surf
This collaborative forecast will be updated Monday through Friday at 300 pm when Pat Caldwell is available.
Collaborative Surf Discussion
SURF HEIGHTS WILL VARY BETWEEN DIFFERENT BEACHES AND AT THE SAME BEACH AT DIFFERENT BREAK AREAS. DISCUSSION: Summary: surf from around the compass. Detailed: mid Wednesday on northern shores has well below seasonal average surf from a mix of sources and directions. Two new events are modelled for Thursday. The pacioos/cdip buoy off Waimea, Oahu mid day 12/17 showed remnant short-period surf from 330-020 degrees and low moderate period surf from 300-320 degrees. The NOAA buoy 51101, 270 nm WNW of Oahu 12/17 shows a downward trend in the 12-16 second bands. A quasi-zonal jet west of the dateline 12/12-15 made for a series of fast-moving, extra-compact surface low pressure cells tracking from near Japan to south of the central Aleutians. Wave model predictions for a deep water swell to 3 feet off Oahu from one of those sources for Wednesday 12/17 was incorrect. With the severe fetch length and duration limitations of the sources combined with the long travel over 1600 nm, odds were low. The last in the series of the extra-compact low cells was the strongest and penetrated further east, passing the dateline near 40°N 12/15. Wave models bring in this short-lived, small event in the wee hours Thursday off Oahu centered on 320 degrees. A larger event is on its heels. The zonal jet west of the dateline gave way to an amplifying trough on 12/14. At the surface, a low pressure cell tracked east from Japan approaching 175°E late Monday with gales over the 290-310 degree band. Seas were near 20 feet. The head of the fetch was about 1500 nm. Small to medium surf from this WNW direction with 14-15 second wave periods should fill in Thursday night and peak early Friday. More northwesterly swell should arrive sooner and get bigger. The system deepened sharply Tuesday night as the low cell crossed the dateline. A compact area of storm to hurricane force winds and a wider area of gales set up over the 310-330 degree band. The low center dropped below 960 mb on Tuesday as it raced NE, passing east of the Hawaii swell window by early Wednesday. The longest fetch was within 315-330 degrees with length and duration limitations due to the fast track across the great circle rays relative to Hawaii. The extreme winds allow long wave periods to develop. Low forerunners with 17-21 second periods are expected to arrive locally near sunrise on Thursday though surf levels should remain below average through the morning. Mid Tuesday 12/16 the head of the fetch with 20-25 feet seas was 1200 nm away, which would bring more significant rising wave energy with 15-17 seconds wave periods near noon on Thursday. Heights are expected to rise above average by the mid afternoon from 315-330 degrees. The fast-moving system should make for a short-lived event for the maximum surf levels, peaking before sunrise Friday. Heights should slow decline on Friday centered near 320 degrees, though with a wide directional swath from 290-320, which was generated by the early stages of the weather pattern west of the dateline 12/14-15, and from 320-350 degrees with the added energy due to angular spreading of the largest swath of seas missing Hawaii to the NE 12/16-17. Heights should fall below average by Saturday dawn from a continued wide directional swath though favoring 320-345 degrees. A new WNW event is due on Sunday. A large surface low pressure deepened rapidly near Japan Tuesday 12/16 with central pressure dipping below 955 mb. A wide fetch of severe gales to hurricane-force winds set up over the 280-300 degree band 12/16-17. Models show the pattern shifting east and maintaining at least storm force with the fetch over the 290-310 degree band reaching the dateline on Friday. Extra-long wave periods of 19-23 seconds from this source should arrive locally overnight Saturday night. This more westerly component swell has greater error bars for the expected surf heights due to shadowing by Kauai on Oahu. The wave energy from 280-310 degrees should peak locally on Sunday at extra-large levels, meaning breakers on outer reefs. Wnw swell should steadily fall Monday into Tuesday, then to below the seasonal average by Wednesday. Additional swell from the eastward-moving weather pattern is expected from NW to N. Models show the large low pressure system with severe gale to storm force strength, tracking ENE across the dateline late Friday. This would add a long fetch over the 310-330 degree band, reaching to near 1000 nm away by mid Saturday. The system is modelled to slow down in track speed as surface winds slowly subside 12/20-22. Proximity makes for large surf. Surf from 310-330 degrees is predicted to fill in early Monday, keeping extra-large surf. It should remain at similar levels into Tuesday. With the mix of swell direction and growing short-period northerly swell, Monday into Tuesday should see extra-rough conditions. Mid Wednesday on eastern shores has declining windswell from 60-90 degrees under moderate trades of similar direction. An increase in both is expected for Thursday. Models show a surface high pressure moving rapidly east, passing north of Oahu near sundown Thursday. This should bring trades back within the fresh to strong bracket. Since existing seas from the previous trade wind event are available, surf should build steadily Thursday to above the trade windswell average from 60-80 degrees. The wind direction should already have more common trade direction of 60-80 degrees on Thursday as the center moves NE of the state, and veer to 70-90 degrees by Friday. Winds are modelled to slowly subside Friday into early Saturday. Surf from windswell should fall below average by Saturday afternoon, and towards small levels on Sunday. See the latest NWS state forecast discussion regarding the changing weather pattern for early next week. Models are suggesting strong breezes from 000-030 degrees behind a front due Monday. This should lead to rough conditions for northerly-facing shores of the east side. Mid Wednesday on southern shores has surf above the December average. Heights are trending down though could remain tiny to small on Thursday from 170-190 degrees. The southern hemisphere SE to E of New Zealand has been in an active austral spring cyclonic mode giving way to above average surf locally. The first event peaked locally 12/15. This event may linger a notch above nil for Friday into Saturday morning from 170-190 degrees as a new event arrives. A severe gale SE of New Zealand 12/12-14 had an eastward track and a weakening trend. The pacioos/cdip buoy off american samoa showed an increase in the 15-17 second energy 12/17. With the 2100 nm distance from this buoy location, that brings forerunners for the surf in locally on Saturday. It should peak on Sunday 12/21 from 180-200 degrees and remain about the same on Monday 12/22. Into the long range, the system east of New Zealand stalled 12/15-17 with marginal gales aimed best at targets SE of Hawaii. It could keep tiny to small breakers locally 12/24-26 from 170-180 degrees. North shores are modelled to remain at extra-large heights on Tuesday 12/23 from 300-350 degrees and slowly drop from 315-350 degrees Wednesday into Thursday 12/24-25 though at levels above the seasonal average. Shorter-period northerly surf is possible 12/23-26 to levels near the seasonal average. The next WNW to NW event is suggested to arrive for the weekend of 12/27 at least near the seasonal average. Long range forecasts are subject to major revisions. This collaborative forecast will resume on Friday, December 19. 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.
Collaborative Surf Table
FORECAST
DATE
SWL
HGT
DMNT
DIR
DMNT
PD
H
1/3
H
1/10
HGT
TEND

PROB
WIND
SPD
WIND
DIR
SPD
TEND
1PM
12/17
3NNW1135DOWN11-16EDOWN
7ENE724DOWN
2S1324DOWN
THU
12/18
4NW1468UPLOW18-22ENEUP
6NW171216UPMED
8ENE846UPMED
2S1223DOWNLOW
FRI
12/19
8NNW141418DOWNHIGH17-21EDOWN
8ENE846DOWNMED
2S1223SAMELOW
SAT
12/20
4NNW1268DOWNLOW7-10ESEDOWN
5E835DOWNLOW
2SSW1735UPLOW
SUN
12/21
11WNW182432UPLOW7-10ESESAME
3E813DOWNLOW
3SSW1546UPLOW
MON
12/22
13NW162836UPLOW22-27NNEUP
8NNE735UPLOW
3SSW1446DOWNLOW
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Collaborative Surf Table Legend

LEGEND:

SWL HGTOPEN OCEAN SWELL HEIGHT MEASURED FROM TROUGH TO CREST IN FEET LOCATED 20 NAUTICAL MILES OFFSHORE
DMNT DIRDOMINANT DIRECTION TYPICALLY +/-10 DEGREES IN 16 COMPASS POINTS
DMNT PDDOMINANT PERIOD IN SECONDS
H1/3SIGNIFICANT WAVE HEIGHT IN THE SURF ZONE
H1/10AVERAGE HEIGHT OF THE HIGHEST ONE-TENTH WAVES IN THE SURF ZONE
HGT TENDHEIGHT TENDENCY OF SWELL (VALID VALUES: UP/DOWN/SAME)
PROBPROBABILITY OF OCCURRENCE (VALID VALUES: HIGH/MED/LOW)
WIND SPDOPEN WATER WIND SPEED MEASURED IN KNOTS LOCATED 20 NAUTICAL MILES OFFSHORE
WIND DIRWIND DIRECTION IN 16 COMPASS POINTS
SPD TENDWIND SPEED TENDENCY (VALID VALUES: UP/DOWN/SAME)
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NWS FORECASTER AND NCDDC PAT CALDWELL

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