PAT CALDWELL

Hazards

HIGH SURF ADVISORY FOR NORTH FACING SHORES

Forecast

Surf along north facing shores will be 10 to 15 feet this evening, decreasing to 9 to 12 feet later tonight, then building back to 10 to 15 feet Tuesday. Surf along west facing shores will be 6 to 10 feet this evening, decreasing to 4 to 6 feet later tonight, then building to 6 to 10 feet Tuesday. Surf along south facing shores will be 3 to 5 feet through Tuesday. Surf along east facing shores will be 1 to 3 feet tonight through Tuesday.

Outlook

Outlook through Monday October 30: The current northwest swell will decline tonight, with a larger northwest swell expected to build Tuesday producing surf around advisory level along north facing shores through Wednesday. An even bigger and long-period northwest swell near the end of the week may produce warning level surf. The south swell will decline over the next few days. 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
10/23
7NW151216DOWN9-13SUP
2ENE812SAME
2SSW1736UP
TUE
10/24
10NNW121016UPLOW13-19NUP
2E812SAMELOW
2SSW1535SAMEMED
WED
10/25
10NNW121016SAMELOW9-13NNEUP
2E923UPLOW
2SE1535UPLOW
2SSW1334SAMELOW
2W2046UPLOW
THU
10/26
7N11610DOWNLOW11-16NNESAME
2E923DOWNLOW
2SE1435SAMELOW
2SSW1224DOWNLOW
2WNW1835SAMELOW
FRI
10/27
11NNW202634UPLOW11-16NESAME
5N1058SAMELOW
5NE724UPLOW
2SE1224DOWNLOW
3WNW1746UPLOW
SAT
10/28
10NNW172028DOWNLOW11-16ENESAME
5NE724SAMELOW
2WNW1535DOWNLOW

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:. Active Fall surf mode. DETAILED:. Mid Monday on has breakers from 310-330 degrees at levels above the active season, October to April, average. Heights are expected to remain elevated on Tuesday. A storm-force low pressure system tracked east along the Aleutians from Kamchatka to the Gulf of Alaska 10/18-21. The long-period swell climbed above average locally by Sunday afternoon. It likely peaked Monday morning. A new, shorter-period event is on its heels. The zonal jet stream pattern across the north Pacific 10/16-20 gave way to a meridional pattern 10/22-23. A sharp trough has formed near 160W. Models show the low pinching off an eddy, which is then forecast to move slowly N to the immediate north of Hawaii. At the surface, a strong high pressure near the Date Line and a surface low below the upper level trough has set up a long, wide fetch of strong to near gale winds, with pockets to low-end gales, nosing to within 500 nm of Hawaii by 10/23. Near gales are expected to continue on the W side of the surface low N of Hawaii 10/24-25. Shorter-period swell of 6-14 seconds should ramp up fast on Tuesday morning from 325-360 degrees. It should remain above average through Wednesday under onshore winds then slowly decline below average by Friday morning, when an exceptionally long- period event should be filled in. Super typhoon Lan became extra-tropical east of the Kuril Islands 10/23. Models show the center moving rapidly NNE to near the western Aleutians late Monday with central pressure dropping below 940 mb on Tuesday. The low is then predicted to track east along the Aleutians, east of the Date Line Wednesday and NE of the Hawaii swell window as it weakens by Thursday. A long fetch of storm- to hurricane-force winds are modelled to set up from near Kamchatka to near the Date Line north of 40N with seas building above 40 feet. As the pattern approaches the Date Line, the more west-to-east surface winds would aim less towards Hawaii. The head of the fetch should reach about 1800 nm away on Wednesday. Wave Watch III model, WW3, shows rare, extra-long-period forerunners greater than 25 seconds filling near dusk Thursday. The event should be filled in by Friday morning from 315-330 degrees with continued exceptionally long wave periods of 18-23 seconds. Wave energy is proportional to wave period, thus the surf is expected to be powerful. Fine-tuning on the explicit surf heights can be made once the event unfolds and satellites for ocean surface winds and waves provides guidance. The event of Friday should reach extra-large levels, which refers to breakers high enough to trip on deep outer reefs, which tend to hold the maximum size. Heights should trend down below extra- large yet remain above average on Saturday from 315-330 degrees. Mid Monday on has breakers from 60-90 degrees at levels below the trade windswell average. Similar surf is expected for Tuesday with rougher, higher conditions for more northerly exposures. ASCAT satellite late Sunday into Monday morning showed an area of fresh to strong trades east of 145W. WW3 picks up the dominant wave period for Wednesday into Thursday, which could mean a pinch more size to the breakers, though less than average. More northerly-component trades are expected to return Thursday into Friday and veer to common ENE by Saturday. Windswell should remain below average from 30-70 degrees Friday into Saturday. Mid Monday on has rising surf at levels above the summer average from 185-200 degrees. Similar surf is likely for Tuesday. A storm-force system sat a bit too close to New Zealand at its maximum of wind strength 10/14-15. The long period swell slowly filled in Sunday into Monday 10/22-23. Once further away from the New Zealand shadow, ocean surface winds weakened to lower end gales, though covered a long, wide fetch 10/16-17. This could keep surf near or a notch below the summer average into Thursday from 180-200 degrees. A compact upper-end gale SE of Easter Island should add surf Weds-Friday from 140-160 degrees to levels near the summer average. Super typhoon Lan while S to E of Japan had a short fetch aimed towards Hawaii. WW3 shows long-period swell starting late Tuesday and holding into Thursday from 280 degrees, then turning more to 290-300 into the weekend. Shadowing by Niihau and Kauai on Oahu increases lessens surf potential. , another typhoon is expected to form in the WPAC this week then turning back to the NE off Japan early next week. That spells odds for more extra-long-period surf going into somewhere in the first few days of November. Before that event, models show a deepening low Saturday near the Dateline, that could bring above average WNW to NNW surf near 10/31. A series of gale low pressure systems tracking east along 60S to the SE of New Zealand within 10/21-27 should make for off and on small, long-period events locally within 10/29-11/4. Peak moments should touch the summer average. Trade windswell is expected to remain below average 10/29-31. Long range forecasts are subject to major revisions. This collaborative forecast will resume on Wednesday, October 25. 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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