PAT CALDWELL

Hazards

HIGH SURF ADVISORY FOR NORTH FACING SHORES

Forecast

Surf along north facing shores will be 12 to 18 feet tonight. Surf will become 10 to 15 feet Tuesday morning, lowering to 8 to 12 feet Tuesday afternoon. Surf along west facing shores will be 3 to 5 feet tonight, lowering to 2 to 4 feet Tuesday. Surf along east facing shores will be 4 to 6 feet tonight with locally higher sets along shores exposed to the north swell. Surf will be 3 to 5 feet Tuesday. Surf along south facing shores will be 1 to 3 feet tonight, and 2 to 4 feet Tuesday.

Outlook

Outlook through Monday November 27: The current north swell will diminish Tuesday. Another large north swell is expected to reach our northern shores Wednesday, peak Thursday, then slowly decline Friday and into the weekend. A High Surf Warning is likely with this swell for all islands with a northern exposure. Another large north swell is forecast to arrive Sunday. Locally generated swell from the strong gusty trade winds during the second half of the work week may warrant a high surf advisory for the east facing shores as well. Waters will turn dangerously very rough and choppy along with the elevated surf. A series of small but long period swells will keep surf from going flat along the south facing shores this 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
11/20
10N121420SAME11-16NSAME
8N968SAME
1SSW1313SAME
TUE
11/21
9NNE111216DOWNMED11-16NNESAME
7NNE957DOWNLOW
1SSW1523UPLOW
WED
11/22
7NNE1068DOWNMED13-19NEUP
6NE624UPLOW
1S1423SAMELOW
11N162230UPLOW
THU
11/23
13NNE142632SAMEMED22-27ENEUP
8NNE968UPLOW
9NE868UPLOW
1S1313SAMELOW
FRI
11/24
11NNE132026DOWNLOW22-27ENESAME
10NE868UPLOW
1S1313SAMELOW
SAT
11/25
7NNE1169DOWNLOW22-27ENESAME
10ENE868SAMELOW
1SSW1834UPLOW

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:. Overlapping N to NNE events. DETAILED:. Mid Monday on has breakers above the Fall seasonal average from 355-010 degrees. Heights should remain above average on Tuesday with a downward trend. The Gulf of Alaska source continues to dominate the surf for Hawaii with N to NNE swell as a blocking ridge near the Date Line keeps WNW to NNW surf near nil. More of the same through the week with hints of a change next week. The rough swell that peaked Sunday was from remote gales and nearby near gales that sent short- to moderate-period swell arriving simultaneously. The moderate period energy of 13-15 seconds is dropping 11/20 while the shorter period swell of 10-12 seconds remains steady, both from the same direction. A strong high pressure just east of the Dateline in combination with the low pressure mostly meridionally-stretched to longitudes east of Hawaii set up a long fetch with strongest winds near the low center near 30N 11/18-20. Fresh to strong breezes have nosed within a few hundred miles of Hawaii and is keeping an active windswell of 6-10 second energy from 350-010 degrees 11/19-20. It should hold into 11/21. The nearby occluded low pressure system moved slowly east 11/18-20. ASCAT satellite Sunday night still showed a large area of near gales aimed at Hawaii over the 000-020 degree band north of 30N that should keep similar surf of 11-13 second periods into Monday night. The Monday morning ASCAT reading showed winds had weakened to within fresh to strong levels, spelling the end of this source. The event should drop below the Fall average by Wednesday with a new long period event due late in the afternoon. The next in the series of low pressure systems in the Gulf of Alaska is much broader and stronger than the pattern that produced the 11/19-20 event locally. The new pattern is similar with the low strongest as it moved SSE from the eastern Aleutians and digging southward fairly close to Hawaii, resulting in both a remote long-period and nearby short- to moderate-period wave energy simultaneously. ASCAT satellite Sunday night showed a wide fetch of severe gales to storm- force winds centered on 160W from the eastern Aleutians southward 800 nm. Models show the dominant wind speed slowly decreasing as gales reach to near 35N on Tuesday. Long-period period swell from the remote source is expected to ramp up sharply late Wednesday afternoon from 355-010 degrees into extra-large levels, meaning high enough for outer reefs. As with the previous system, near gales are modelled to reach to at least 30N into Wednesday morning. This will add to the long- period swell more shorter-period energy from 000-020 degrees locally by Thursday, making for disorganized breakers. The event is expected to peak on Thursday and remain extra- large with a wide wave period band from 000-020 degrees into Friday morning. Models show the low pressure system weakening sharply as it lifts out to the east 11/22-23. This should mean a steady decline to the locally surf from 000-030 degrees Friday with heights below average by Saturday. Mid Monday on has minimal energy from 45-90 degrees. More northerly exposures should have active breakers and should trend aforementioned. The magnitude and NNE direction is allowing breakers to refract and diffract it to more pure easterly exposures. See the latest NWS State Forecast Discussion regarding the trend in local winds and weather. Strong surface high pressure is modelled to sit NNW to N of Hawaii 11/23-25 producing strong trades from 050-070 degrees. The upstream fetch is expected to be short, not more than about 600 nm long, so the dominant wave period should not grow as much. The wind magnitude should be enough to bring breakers from windswell above the trade windswell average starting Thursday and holding into the weekend. But the size of the breakers would be lower than expected given the local wind speed. Mid Monday on has a slither of moderate-period swell from 180-200 degrees making inconsistent, small breakers at zones of high refraction, while mostly flat for most exposures. Similar surf is expected on Tuesday A long-lived area of marginal gales SE of New Zealand 11/13-16 could keep similar low surf for the high refraction zones through the week. A stronger system with seas to 25 feet tracked zonally along 60S to the SE of New Zealand 11/17-19. It could give longer period swell starting Saturday from 190-200 degrees, which in turn would give higher breakers. , the low, long-period SSW should peak 11/26 then fade out by 11/28. Southerly surf should return to the seasonal near nil within 11/29-12/1. Models show another storm-force system in the Gulf of Alaska starting Thursday night. Forerunners are due Sunday morning from 010-020 degrees with breakers climbing above average in the afternoon. It should peak 11/27 then slowly drop below average by 11/28. Models suggest the jet stream block at the Date Line near the Aleutians to break down and allow a series of jet level short-wave troughs and their associated surface low pressures to track east from the Kuril Islands to north of Hawaii. It is too early for specifics, but in general, a return to seasonal NW swell within 11/29-12/4. Above average windswell should continue 11/26-27 from 60-90 degrees. Long range forecasts are subject to major revisions. This collaborative forecast will resume on Wednesday, November 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 http://www.prh.noaa.gov/hnl/pages/marine.php

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NWS Forecaster and NCEI Pat Caldwell

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