PAT CALDWELL

Hazards

No high surf advisory or warnings.

Forecast

Surf along south facing shores will be 2 to 4 feet through tonight, then will increase to 3 to 5 feet Friday. Surf along east facing shores will be 3 to 5 feet through early Friday, then will decrease to 2 to 4 feet late Friday. Surf along north facing shores will be 2 feet or less through Friday. Surf along west facing shores will be 3 feet or less through Friday.

Outlook

Outlook through Thursday August 24: Surf is expected to trend down along east facing shores this weekend as the trades weaken slightly. A small south-southeast swell is expected to peak late Friday, and then gradually subside this weekend. A small, long-period southwest swell is forecast to arrive Saturday, and continue into early next week. Surf will likely remain below the High Surf Advisory criteria along all shores through the middle of 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.

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 08/16	6	ENE	8	3	5	SAME		13-19	ENE	DOWN
	1	S	16	2	3	SAME
THU 08/17	5	ENE	8	3	4	DOWN	LOW	12-18	ENE	DOWN
	1	S	14	2	3	DOWN	LOW
	1	SSE	17	2	4	UP	LOW
FRI 08/18	4	ENE	8	2	3	DOWN	LOW	11-16	ENE	DOWN
	2	SSE	15	3	5	UP	LOW
SAT 08/19	4	E	7	1	2	DOWN	LOW	11-16	E	SAME
	2	SSE	14	3	5	DOWN	LOW
SUN 08/20	4	E	7	1	2	SAME	LOW	11-16	E	SAME
	2	SSE	12	2	4	DOWN	LOW
MON 08/21	5	E	8	2	4	UP	LOW	11-16	E	SAME
	2	SE	10	2	3	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:. Summer surf from E and S. DETAILED:. Mid Wednesday on has breakers from 50-90 degrees at levels near the trade windswell average. A decrease is predicted for Thursday. Surface high pressure near 40N, 140W is weakening and drifting east. ASCAT satellite still showed some pockets to fresh trades well ENE of Hawaii into Tuesday night. This should keep the dominant wave period near the 8 second mark, which is elevated enough to allow declining surf into Friday from within 50-90 degrees. Breakers should be near a trade windswell minimum by Saturday. See the latest NWS State Forecast Discussion regarding the trend in trades. An area of enhanced tropical convection SE of the Big Island is being monitored for influence on local wind, weather, and waves for Sunday into Monday. A nominal local wind estimate is given in the table above for 8/20-21. Stay tuned for updates. Mid Wednesday on has near nil surf except for locations susceptible to trade windswell. Similar conditions are expected for Thursday. No surf is expected in Hawaii from tropical cyclone Banyan in the NW Pacific. Mid Wednesday on has infrequent breakers from 170-190 degrees at levels below the summer average. Similar surf is likely for Thursday. The austral polar jet stream steered a low pressure system hugging Antarctica eastward across the Hawaii SSW to S swell window 8/7-8. Buoys 51004 to the SE of Hawaii is showing the most energy in the 15-16 second band relative to 51002 and 51003, indicating the event mostly missing Hawaii to the east. Since the dominant wave periods are still elevated, there should be one more day of similar or slightly less surf from this source. This same low pressure tracked NE 8/9 and occluded 8/10 to the SE of French Polynesia. A compact area of severe gales to storm-force winds aimed at Hawaii over the 155-165 degree band. The system weakened 8/11-12. The swell source had French Polynesia on its path to Hawaii. These islands cause partial shadowing and increase error bars for the local surf estimate. Long-period forerunners are due on Oahu Thursday 8/17 from 155-170 degrees. It should be filled in by Friday...peaking late Friday near the summer average, and dropping slowly into Sunday. Surf should return to the southern hemisphere trade windswell as the dominant source by Monday. Into the long range, a strong high pressure south and a subtropical low ESE of French Polynesia has set up strong trades within 20-30S, 135-150W 8/14-16. It is expected to last another few days. This should be the dominant background surf next week 8/22-25 from 140-160 degrees. This event should be a notch larger than the typical austral trade windswell. Models show an increase in trades E to NE of Hawaii 8/21-23, that should trend up breakers from windswell out of 50-90 degrees at the same time. This collaborative forecast will resume on Friday, August 18. 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