PAT CALDWELL

Hazards

No high surf advisory or warnings.

Forecast

Surf along north facing shores will be 3 to 5 feet tonight, and 2 to 4 feet Sunday. Surf along west facing shores will be 1 to 3 feet tonight, and 2 feet or less Sunday. Surf along east facing shores will be 3 to 5 feet through Sunday. Surf along south facing shores will be 1 to 3 feet through Sunday.

Outlook

Outlook through Saturday April 27: A small, long-period west-northwest swell is expected Monday through Wednesday. Surf is expected to increase a bit along south facing shores Monday, and hold steady through midweek. Surf along east facing shores will remain up into the early part of next week due to the trades. 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.

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 04/19	4	NNW	13	6	8	UP		13-19	E	UP
	7	E	6	2	4	UP
SAT 04/20	3	NNW	11	4	6	DOWN	MED	17-21	E	SAME
	7	E	7	3	4	UP	LOW
SUN 04/21	2	NNW	10	1	3	DOWN	LOW	13-19	E	DOWN
	7	E	7	3	4	DOWN	LOW
MON 04/22	2	NNW	10	1	3	SAME	LOW	13-16	E	SAME
	6	E	7	2	4	SAME	LOW
	2	S	16	3	5	UP	LOW
TUE 04/23	2	NW	10	1	3	SAME	LOW	13-19	E	SAME
	6	E	7	2	4	SAME	LOW
	2	S	15	3	5	SAME	LOW
WED 04/24	2	NNW	10	1	3	SAME	LOW	13-19	E	SAME
	6	E	7	2	4	SAME	LOW
	2	S	14	3	4	SAME	LOW

Collaborative Surf Table Legend

LEGEND:

SWL HGT	Open ocean swell height measured from trough to crestin feet located 20 nautical miles offshore
DMNT DIR	Dominant direction typically +/-10 degrees in 16 compasspoints
DMNT PD	Dominant period in seconds
H1/3	Significant wave height in the surf zone
H1/10	Average height in the highest one-tenth waves in the surfzone
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 located20 nautical miles offshore
WIND DIR	Wind direction in 16 compass points
SPD TEND	Wind 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... Low Spring mode. DETAILED:. Mid Friday on has breakers from 325-345 degrees at levels a notch below the April average. Heights are predicted to trend down late Friday into Saturday. A wide, long fetch of strong to near gale breezes followed a SE- pushing front from near the Date Line on the Aleutians Sunday 4/14 to about 1000 nm away from Hawaii late 2/16. The system moved east of the Hawaii swell window Wednesday 4/17. NOAA NW Hawaii buoys 51001 and 51101 showed a sharp rise to a maximum in the 12-14 second band Thursday evening 4/18. The wave energy has been trending down towards noon 4/19. The PacIOOS/CDIP Hanalei, Kauai buoy reached 6 feet deep water swell Friday morning though peak heights at the Waimea, Oahu buoy have been lower within 3-4 feet 4/19 AM. With the large generation area, the event should linger at small levels Saturday from 325-345 degrees then drop to tiny to small levels by Sunday. A weak, zonal jet stream within 30-45N across the central north Pacific became established 4/17. A weak low pressure near 40N, 170W 4/18-19 could keep tiny to small NNW breakers on Monday 4/22. Another weak low pressure area west of the Date Line near 35N, 170E 4/18-19 is tracking NE. It should keep a tiny to small WNW to NNW event locally 4/23-24. Mid Friday on has breakers from 70-90 degrees at levels below the trade windswell average. Heights are expected to rise slightly on Saturday. The fetch of trades aimed at Hawaii stretches well to the east of the islands beyond 1000 nm with strong breezes south the latitudes of the islands, fresh breezes along the zonal band within the islands, and gentle to moderate breezes just north of the latitude of the islands. This is narrowing the fetch aimed at Oahu for the fresh breezes necessary for making windswell. Wind models suggest a slight maximum to the trades on Oahu for Saturday 4/20 that should coincide with a notch more size in the breakers. Heights should hold near to below average 4/21-23 from 70-90 degrees. Mid Friday on has wave energy from the southern hemisphere at a minimum. Low conditions are expected to continue on Saturday. Weak low pressure systems S to SE and E of New Zealand 4/11-13 did not have sufficient strength to send surf beyond background to Hawaii. Wave Watch III does show the dominant background swell direction turning into the New Zealand window near 190 degrees by Saturday 4/20 into 4/21. Better odds for surf building Monday. The jet stream formed a large meridional, or north to south, loop east of New Zealand 4/14-17. At the surface, low pressure areas filled 35-70S south of French Polynesia while high pressure set up over New Zealand. This long, wide fetch had direct aim at Hawaii over the 175-185 degree band. The limiting factor was the wind magnitude, which was mostly strong to near gale winds with pockets to marginal gales. The PacIOOS/CDIP American Samoa buoy picked up the new swell 4/18-19 with deep water swell 6-7 feet with 12-16 second energy. Since this is at the short end of the swell spectrum, and shorter wave period energy loses height more rapidly with travel distance due to greater angular spreading, the potential for surf in Hawaii is lower. A similar reading at Samoa with 16-20 second energy would mean a significant, above average event in Hawaii. The event is predicted to fill in Monday 4/22 to levels near the seasonal average. It should hold about the same on Tuesday with a downward trend Wednesday. , there was a second fetch area of near gales 4/17-18 that should keep surf at upper-end background levels locally Thursday 4/24 into 4/25. The overall long-wave trough pattern shifted east south of French Polynesia 4/17-19 with sources better aimed at the Americas. Angular spreading should keep upper-end background surf rolling into the weekend of 4/27 locally out of 170-180 degrees. On the north shore, surf should remain at a seasonal minimum 4/24-25. East side should hover about the same a notch below the average. Long range forecasts are subject to high uncertainty. This collaborative forecast will resume on Monday, April 22. 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 https://www.weather.gov/hfo/marine

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NWS Forecaster and NCEI Pat Caldwell