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SRFHFO

SURF ZONE FORECAST
NATIONAL WEATHER SERVICE HONOLULU HI
331 AM HST SUN JUL 22 2018

OAHU-
331 AM HST SUN JUL 22 2018

HIGH SURF ADVISORY FOR SOUTH FACING SHORES

Surf along east facing shores will be 4 to 6 feet through Monday.

Surf along south facing shores will be 5 to 8 feet through Monday.

Surf along west facing shores will be 4 to 6 feet through Monday.

Surf along north facing shores will be 2 feet or less through Monday.

Outlook through Sunday July 29: The current long-period south swell will gradually lower from Monday night through Tuesday. Small south swells will maintain background surf along south facing shores from mid-week into next weekend. The trade winds will continue to produce moderate short-period choppy surf along east 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.


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SRDHFO

COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
NWS/NCDDC HONOLULU HI
302 PM HST FRI JUL 20 2018

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
07/20
5ENE834DOWN11-16ENEDOWN
2S1746SAME
SAT
07/21
5ENE724SAMELOW11-16ENESAME
2S1746SAMELOW
2SSE2247UPLOW
SUN
07/22
5ENE724SAMELOW11-16ENESAME
3S19810SAMELOW
MON
07/23
5ENE724SAMELOW11-16ENESAME
3S1768DOWNLOW
TUE
07/24
5ENE724SAMELOW11-16ENESAME
2S1535DOWNLOW
WED
07/25
2NE1124UPLOW11-16ENESAME
5ENE724SAMELOW
2SSE1324DOWNLOW

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... East side holding steady below average while south side tops the heights.

DETAILED:. Mid Friday on eastern shores has declining breakers from 60-90 degrees at levels below the trade windswell average. Conditions should remain low on Saturday.

See the latest NWS State Forecast Discussion for an explanation of the trends in the local winds and skies.

ASCAT satellite overpass in the morning 7/20 shows a large area of gentle to moderate breezes in the trade windswell source region to the E to NE of Hawaii. The moderate pattern is expected to hold other than smaller scale, transient features to fresh levels. The local windswell is predicted to remain below average through the period.

Low, longer-period windswell is due Wednesday from 40-60 degrees. It is being generated by strong to near gale winds west of northern California.

Mid Friday on southern shores has breakers from 175-190 degrees at levels a notch above average. Similar surf is predicted for Saturday.

A series of overlapping events have kept active surf locally since 7/17. Similar overlapping events are expected to continue into early next week.

The PacIOOS/CDIP Barbers Point buoy shows the dominant direction near straight south on 7/20. The source was an area of seas greater than 30 feet to the SSE of New Zealand 7/12 with aim at the Americas. A great circle line from Hawaii to the source is 190 degrees. However, the angular spreading causes the swell direction upon arrival in Hawaii to have more straight south component.

NOAA southern buoy 51002 7/20 mid morning showed the peak in this event in the 15-16 second band. This should arrive locally near near sundown as the maximum for this source.

The next austral, mid latitude low pressure 7/13-14 strengthened and gained more northward aim to the fetch as it reached the eastern edge of the Hawaii swell window south of French Polynesia. The near miss makes for greater error bars on the local surf estimate.

Buoy 51001 is showing the long-period forerunners arriving 7/20. This event should be filled in by Saturday, keeping surf about the same from 170-190 degrees.

The final austral source 7/15-17 was the strongest and had the best aim towards Hawaii at the eastern edge of the Hawaii swell window. It had a wide area of seas over 30 feet with peak seas to 40 feet. The system moved steadily east away from the Hawaii swell window.

Extra-long wave periods of 20-25 seconds are predicted to slowly fill in locally on Saturday, making for inconsistent sets. It should be filled in by Sunday from 165-185 degrees to levels above average, peak Sunday night, and slowly drop to average levels from the same direction by Tuesday. Background level conditions are expected to take over by Wednesday.

Into the long range, below average surf from southern sources is expected 7/26-28. Windswell from the east will depend on the tropical activity to the E to SE of Hawaii. Otherwise, windswell from the semi-permanent high pressure in the central to northeastern north Pacific should keep breakers near to below average from 60-90 degrees.

Long range forecasts are subject to high uncertainty.

This collaborative forecast will resume on Monday, July 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

NWS Forecaster and NCEI Pat Caldwell

Additional Resources:

Waimea Buoy Kailua Buoy Lanai Buoy Barbers Point #2 Pauwela, Maui Hilo Bay Buoy Kaneohe Bay Buoy Hanalei Kauai Buoy Kilo Nalu
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

Tides for Honolulu

Tide tables for Hawaii