PAT CALDWELL

Hazards

HIGH SURF WARNING FOR NORTH AND EAST FACING SHORES

Forecast

Surf along north facing shores will rise rapidly, reaching heights of 25 to 30 feet tonight with occasional sets to 35 feet on outer reefs. Surf will continue at these heights through Thanksgiving Day. Surf along west facing shores will be 3 to 5 feet tonight through Thanksgiving Day. Surf along east facing shores will be 10 to 15 feet through Thanksgiving Day. Surf along south facing shores will be 1 to 3 feet through Thanksgiving Day.

Outlook

Outlook through Wednesday November 29: The large north swell will decline slowly Thursday night and Friday. Increasing, strong trades will result in rough conditions along east facing shores. Another large north swell may arrive Sunday and continue into early next week. 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, at the locations of the largest breakers. 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.

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R Ballard

About Collaborative Surf

This collaborative forecast will be updated Monday through Friday at 300 PM when Pat Caldwell is available.

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
11/22
9N111014SAME13-19NEUP
7NNE846SAME
THU
11/23
14N142836SAMEMED22-27NESAME
10NNE868SAMEMED
FRI
11/24
12NNE132228DOWNLOW22-27NESAME
10NE868SAMEMED
SAT
11/25
8NNE111216DOWNLOW19-23ENEDOWN
10NE868DOWNLOW
1SSW1824UPLOW
SUN
11/26
5N17812UPLOW19-23ESAME
9ENE968SAMELOW
1S1624SAMELOW
MON
11/27
8NNE141418DOWNLOW17-21EDOWN
9E968DOWNLOW
1S1413DOWNLOW

Collaborative Surf Table Legend

LEGEND:

SWL HGTOpen ocean swell height measured from trough to crestin feet located 20 nautical miles offshore
DMNT DIRDominant direction typically +/-10 degrees in 16 compasspoints
DMNT PDDominant period in seconds
H1/3Significant wave height in the surf zone
H1/10Average height in the highest one-tenth waves in the surfzone
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 located20 nautical miles offshore
WIND DIRWind direction in 16 compass points
SPD TENDWind speed tendency (valid values: UP/DOWN/SAME)

Disclaimer

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

Collaborative Surf Discussion

DISCUSSION: SUMMARY:. Steady N to NE above-average surf. DETAILED:. Mid Wednesday on has breakers above the Fall average from 355-030 degrees. An sharp increase is expected late Wednesday. The north Pacific jet stream has maintained a blocking ridge near the Date Line over the Aleutians and troughs or cut-off lows in the Gulf of Alaska for a few weeks. This has kept dominant N to NNE surf for most of November. The next rise in surf is due late Wednesday 11/22. It is expected to rapidly build to extra-large levels, meaning high enough to break on outer reefs. With this magnitude, refraction and diffraction into western and eastern facing shores is expected during the larger portions of the event. It was generated by a storm-force low pressure system that dug SSE from SW of Anchorage, Alaska, 11/19 setting up a captured fetch over the 000-020 degree band. As the fetch stretched southward, the wind speeds slowly decreased with severe gales to near 45N and gales to 35N by 11/21. Models show the low weakening 11/22 it moves towards the west coast of the USA. The JASON altimeter validated well the Wave Watch III model output for the seas of 20-25 feet in the region 35-45N to the NNE of Hawaii. Even when the wave model validates well at the remote source, the model tends to bias low for the output point at the Waimea buoy; hence the numbers above are nudged up a notch or two. Long-period swell of 14-17 seconds is slowly climbing mid to late morning 11/22 at the NOAA NW Hawaii buoys and the PacIOOS Hanalei buoy. It should climb into extra-large levels on Oahu within sundown to midnight 11/22 from 355-020 degrees. Short- to moderate-period wave energy from 000-030 degrees generated by near gales that nosed to 30N on 11/21 and increasing strong breezes to 23N 11/22, respectively, both N to NNE of Hawaii, should also arrive on Thursday, making for disorganized breakers. Extra-large surf conditions are expected to hold into Friday morning with a downward trend to near average by mid Saturday, and below average late Saturday. By early Sunday, forerunners from a new N event are due to arrive. Models show a new storm-force system tracking SSE from the eastern Aleutians early Thursday 11/23. It is expected to occlude in the Gulf of Alaska and keep a nearly stationary surface low pressure to severe gale strength through Friday, slowly weaken to gale Saturday, then lift out to the east on Sunday. It should make for a long-lived surf event locally. The surf should build Sunday morning from 000-020 degrees, reaching the Fall average by Sunday afternoon, peak morning, and remain above average through Monday from the same direction. Mid Wednesday on has above average breakers for more northerly exposures. The longer period N to NNE swell should keep active breakers through the period with trends aforementioned. See the latest NWS State Forecast Discussion for an explanation of the weather features affecting the local winds and weather through the period. The local windswell is expected to veer on the compass through the period with more NNE direction 11/22 into 23, NE 11/23-24, NE to ENE 11/24-25, and ENE to E 11/26-27. Rough breakers at levels above the trade windswell average are expected through the period. Mid Wednesday on has mostly flat conditions with tiny to small breakers at zones of high refraction. Similar conditions are predicted 11/23-24. A severe-gale grew seas to 25 feet as a system tracked east along 60S to the SE of New Zealand 11/17-19. Angular spreading could bring in low, long-period swell from 180-190 degrees making for small breakers at high refraction zones late Saturday into Monday. Most areas should remain flat to tiny. , back to seasonal near nil for southern hemisphere swell 11/28-30 with dominant breakers refracting E windswell with size depending on exposure. In the north Pacific, the long-lived Date Line jet stream block is predicted to give way to a zonal pattern embedded with fast- moving short-wave troughs. At the surface, gales to storm-force systems are modelled to track east just south of the Aleutians with about a 2-3 day spacing. The first one is predicted to intensify near the Date Line Saturday night and bring an above average NNW event filling in late 11/28 and peaking 11/29. The second one is suggested to be larger and fill in 11/30, peaking 12/1, also mostly NNW. Easterly windswell should remain near or above average from 60-90 degrees within 11/28-30. Long range forecasts are subject to low confidence. This collaborative forecast will resume on Friday, November 24. This forecast was produced through the collaborative efforts of NWS and NCEI. Please send suggestions to w-hfo.webmaster@noaa.gov or call the Warning Coordination Meteorologist at 808-973-5275. ADDITIONAL RESOURCES: See http://www.prh.noaa.gov/hnl/pages/marine.php

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NWS Forecaster and NCEI Pat Caldwell

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