National Weather Service United States Department of Commerce

Surf Forecast for Oahu  Issued: 08/21/2019 03:35:58 AM HST

Surf Discussion for Oahu  Issued: 08/19/2019 02:59:53 PM HST


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SURF ZONE FORECAST
NATIONAL WEATHER SERVICE HONOLULU HI
335 AM HST WED AUG 21 2019

OAHU-
335 AM HST WED AUG 21 2019

HIGH SURF ADVISORY FOR SOUTH FACING SHORES

Surf along south facing shores will be 6 to 10 feet today, lowering to 5 to 8 feet tonight, then lowering to 4 to 6 feet Thursday.

Surf along west facing shores will be 4 to 7 feet today, lowering to 3 to 5 feet tonight, then lowering to 2 to 4 feet Thursday.

Surf along east facing shores will be 2 to 4 feet today and tonight, lowering to 2 to 3 feet Thursday.

Surf along north facing shores will be 1 to 3 feet today, rising to 2 to 4 feet tonight and Thursday.

Outlook through Wednesday August 28: The current long-period south swell will hold steady today, then gradually lower tonight into the weekend. A series of small long- period south and southwest swells will move through Sunday through early next week. A larger southwest swell is possible Tuesday through the middle of next week. Small northwest swells will linger over the next few days providing some out of season surf along north facing shores. Strengthening trade winds will give a boost in short period choppy surf along east facing shores through tonight and again over the weekend.

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.


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COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
NWS/NCDDC HONOLULU HI
259 PM HST MON AUG 19 2019

This collaborative forecast will be updated Monday through Friday at 300 PM when Pat Caldwell is available.

FORECAST
DATE
SWL
HGT
DMNT
DIR
DMNT
PD
H
1/3
H
1/10
HGT
TEND

PROB
WIND
SPD
WIND
DIR
SPD
TEND
1PM
08/19
2WNW1123DOWN9-13NESAME
2SW1224SAME
TUE
08/20
2WNW1013DOWNLOW11-16ENEUP
5ENE613UPLOW
5SSW181015UPLOW
WED
08/21
5ENE724SAMELOW11-16ENESAME
5SSW17815DOWNLOW
THU
08/22
4ENE712DOWNLOW9-13NEDOWN
4SSW1468DOWNLOW
2NW1334UPLOW
FRI
08/23
3NW1135SAMELOW11-16EUP
5E613UPLOW
2SSW1334DOWNLOW
SAT
08/24
2NW1023DOWNLOW13-19EUP
5E724UPLOW
2S1224SAMELOW

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)

Compass & Swell Shadow Lines for Hawaii

Oahu Surf Climatology

Surf heights will vary between different beaches and at the same beach at different break areas.

DISCUSSION: SUMMARY:. Large south swell.

DETAILED:. Mid Monday on southern shores has breakers from 140-220 degrees at levels below the seasonal average. An increase is due late Monday above average.

A low pressure system SE of New Zealand near 60S, 180E 8/13 tracked NE to near 45S, 170W into 8/14. Storm-force winds were validate by satellite to track NE as a captured fetch within the 185-200 degree band aimed at Hawaii. Maximum seas to near 40 feet were confirmed by an altimeter. The system moved steadily east 8/15-16 out of the Hawaii swell window.

The PacIOOS/CDIP American Samoa buoy showed energy in the 16-22s bands starting late 8/16 into 8/17 at levels higher than the event that caused the high surf locally July 13-14, 2019. The mid July source had a wider fetch, which allows less swell decay with distance. Thus, the net result should be events locally of similar magnitude.

As of noon 8/19, the NOAA southern buoys do not show much more than a slither of energy in the 18-22+s bands. The PacIOOS/CDIP Barber's Point does show a trickle upward in the same long-period band Monday morning. The Lanai buoy is rising faster. It is common for New Zealand source events to be larger eastward along the Hawaiian archipelago.

The onset stage locally should occur into dawn Tuesday, with a steady rise in consistency and size during the day from 185-200 degrees. It should peak Tuesday night with elevated heights through Wednesday. Heights should trend down more rapidly on Thursday, to levels below average by Friday from 180-200 degrees. Background level conditions should be the rule by Saturday.

Keep in mind the large spread in breaker sizes that can occur from remote systems, since the sets can be spaced further apart by dispersion during the long travel. This can lead to a false sense of security during the lower spells, with the larger spells arriving fast and furious.

Mid Monday on western shores has tiny to small breakers from 270-300 degrees. Heights should decline from this direction on Tuesday as southerly exposures rise aforementioned.

The long-lived typhoon Krosa swell is still being registered at the PacIOOS nearshore buoys off Hanalei, Kauai and Oahu's north and south shores. Krosa weakened as it tracked NE toward Japan 8/11-14. Tiny to small breakers could hold on for another day for exposures to 270-300 degrees into Tuesday 8/20.

Mid Monday on northern shores has tiny to small breakers for select western exposures from the Krosa source. Heights should favor tiny levels on Tuesday.

A mid latitude low pressure system occluded 8/19 near 42N, 175E or about 1700 nm away from Hawaii. Models have downgraded the surf potential locally since the system is predicted to remain stationary longer than earlier expected and not maintain enough surface wind magnitude as it lifts off the the NE 8/21-22. It is still more active than typical for an extra-tropical system in mid August.

Small surf is expected to build Thursday PM from 310-320 degrees. It should peak early Friday then trend down to tiny levels on Saturday.

Mid Monday on eastern shores has breakers at a minimum. A slight increase is possible on Tuesday.

See the latest NWS State Forecast Discussion for an explanation of the weather features driving the local trades and skies this week.

The breakers from windswell should climb a notch from 50-70 degrees 8/20-21 though to levels below the trade windswell average. Another mild increase is predicted for Saturday from 70-90 degrees.

Into the long range, breakers from windswell could reach average levels within 8/25-27 from 70-90 degrees.

Northern shores are expected to return to typical summer levels near nil.

Southern shores are estimated to rise within 8/27-28 out of 208-220 degrees from a Tasman Sea Source. The pattern expected to unfold east of Australia 8/20-23 has about as good as it gets for surf potential in Hawaii from the Tasman, since the high seas are modelled to reach into the sub-tropics, closer to Hawaii. This could bring surf locally above average 8/28-29.

Long range forecasts are subject to major revisions.

This collaborative forecast will resume on Wednesday, August 21.

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

NWS Forecaster and NCEI Pat Caldwell

Additional Resources:

Waimea Buoy Mokapu Point Buoy Kaumalapau SW Lanai Buoy Barbers Point, Kalaeloa Buoy Pauwela, Maui Hilo Bay Buoy Kaneohe Bay Buoy Hanalei Kauai Buoy Pearl Harbor Entrance
Buoy 51001 Buoy 51101 Buoy 51000 Buoy 51100 Buoy 51002 Buoy 51003 Buoy 51004

Latest North Pacific Surface Analysis

Upcoming tides for select Hawaii locations

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