PAT CALDWELL

Hazards

No high surf advisory or warnings.

Forecast

Surf along north facing shores will be 3 to 5 feet tonight, building to 5 to 7 feet Saturday. Surf along west facing shores will be 2 to 3 feet tonight, building to 3 to 5 feet Saturday. Surf along east facing shores will be 3 to 5 feet through Saturday. Surf along south facing shores will be 3 to 5 feet through Saturday.

Outlook

Outlook through Friday April 27: The current northwest swell will boost surf along north and west facing shores Saturday. A slightly larger swell will peak Sunday and another moderate swell is possible next Thursday. A series of small swells from the southern hemisphere will maintain modest surf along south facing shores chain through this weekend. Lows in the southern hemisphere may strengthen and shift east enough to produce some bigger surf along south facing shores by the end of next week. Rough surf will persist along east facing shores through Sunday night due to the locally strong trade winds, but heights will remain moderate through the weekend. As trade winds strengthen early next week, surf may approach the High Surf Advisory threshold along east 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, 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
04/20
2NNW1424UP13-19ENESAME
7ENE846SAME
2SSW1324DOWN
SAT
04/21
4NNW1268SAMELOW13-19ENESAME
6ENE835DOWNLOW
2SSW1534UPLOW
SUN
04/22
3NNW1135DOWNLOW17-21ENEUP
3NW1758UPLOW
7ENE735UPLOW
2SSW1434SAMELOW
MON
04/23
5NNW15810SAMELOW17-21ENESAME
7ENE846UPLOW
2SW1634UPLOW
TUE
04/24
4NNW1268DOWNLOW19-23ENEUP
8ENE857UPLOW
2SW1534SAMELOW
WED
04/25
3NNW1046DOWNLOW19-23ENESAME
9ENE868UPLOW
2SW1534SAMELOW

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:. Spring conditions. DETAILED:. Mid Friday on has small breakers from 315-330 degrees. An increase is expected late Friday. The longer wave period phase of the new episode arrived 4/19-20 slower and smaller than modelled by the Wave Watch III. The source was to storm force as it approached the Date Line south of the Aleutians 4/16, though surface winds were west to east, not well aimed at Hawaii. The system was slow-moving with a wide area of low-end gales 4/17-18 within 40-50N, 160-180W. The shorter to moderate wave period phase of this event has better odds of matching model output since it had more direct aim at Hawaii. The head of the fetch was over 1500 nm away, so the size should remain below the April average as it peaks on Saturday centered near 320 degrees. It should slowly decline into Sunday as a new event arrives. The next low pressure deepened east of the Kuril Island 4/19, reaching storm force as it arrived at 40N, 170E, or about 2000 nm away from Hawaii. It maintained strength 4/20 as the head of the fetch pushed east of the Date Line north of 40N. Models show it moving east of the Hawaii swell window 4/21. Long-period swell should arrive locally near sundown Sunday with a steady increase to above the April average overnight. It should peak on Monday above average from 305-330 degrees. It should slowly drop below average by Tuesday and fade out Wednesday from the same direction. Mid Friday on has breakers from 60-90 degrees at levels above the trade windswell average. Heights are expected to drop slightly to near the average on Saturday. Surface high pressure has held the zonal band from west of the Date Line to the NE Pacific with 30-40N over the past week. More of the same is predicted this period. Steady easterly swell is expected to hold with heights near the average over the weekend from 60-90 degrees and trending up early next week. The center of a strong high pressure cell is modelled to settle NNE of Hawaii Monday into Tuesday with a increase in local and upstream trade winds to the E to NE. This should increase breakers from windswell Monday into Wednesday above average from 40-90 degrees. Mid Friday on has background conditions with small breakers from 180-220 degrees for high refraction zones and near flat conditions every where else. A slight increase is predicted for Saturday. Select exposures to the trade windswell should remain active through the period. A severe gale just north of Antarctica to the SE of New Zealand 4/12-14 has potential to bring in a low, long-period swell for the weekend of 4/21-22 locally from 180-190 degrees. Heights should remain at background levels. Active mid latitude cyclones in the southern Tasman Sea starting 4/15 should be the dominant background surf for Monday to Wednesday 4/23-25 from 200-220 degrees. , models show the low pressure area that has hovered over and been shadowed for waves by New Zealand this week to shift eastward. This should place gales over the 190-200 degree band late 4/20 into 4/22. This increases odd for surf near the summer average building late 4/28 locally and peaking 4/29. Models suggest a similar pattern E to SE of New Zealand 4/24-25 to make a similar SSW event locally around 5/1-3. In the north Pacific, models show a broad area of gales south of the Aleutians moving slowly near the Date Line 4/23-25. This should trend surf up to near the April average by 4/27 locally, holding into the weekend of 4/28 from 315-330 degrees. Above average easterly windswell is predicted for 4/26 though models suggest a downward trend from 60-90 degrees into the weekend of 4/28. Long range forecasts are subject to low confidence. This collaborative forecast will resume on Monday, April 23. 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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