Surf Forecast for O`ahu

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SRFHFO

SURF ZONE FORECAST
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST SUN SEP 24 2017

OAHU-
330 AM HST SUN SEP 24 2017

Surf along south facing shores will be 2 to 4 feet through Monday.

Surf along west facing shores will be 2 to 4 feet through Monday.

Surf along east facing shores will be 1 to 3 feet through Monday.

Surf along north facing shores will be 3 to 5 feet through Monday.

Outlook through Sunday October 01: A small northwest swell will hold before easing Monday, followed by a small reinforcement through midweek. Small surf will persist along south facing shores due to a mix of small southeast and southwest swells. Surf along east facing shores will slowly trend down as the trades weaken.

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
250 PM HST FRI SEP 22 2017

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
09/22
3WNW1135SAME11-16ENEDOWN
5ENE834SAME
2SE913SAME
SAT
09/23
3NW1135SAMELOW9-13ENEDOWN
4ENE824DOWNLOW
2SE913SAMELOW
SUN
09/24
3NNW1135UPLOW7-10ENESAME
3ENE712DOWNLOW
2SW1434UPLOW
MON
09/25
3NNW1035DOWNLOW7-10ESAME
2SW1434SAMELOW
TUE
09/26
3NW1135UPLOW7-10ESAME
2SW1224DOWNLOW
WED
09/27
3NNW1035DOWNLOW9-13ENEUP
2SE913SAMELOW

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:. Low spell.

DETAILED:. Mid Friday on southern shores has near flat breakers with dominant surf from trade windswell out of both hemispheres. Similar surf is likely for Saturday.

The summer season ended without a single significant event from the primary quadrant of 185-200 degrees, which is the New Zealand source and climatologically, the dominant southerly swell direction. There were 3 significant events late April, late May, and last week of Spring from SSW. The few events that did arrive during the summer were from within 150-185 or 208-220 degrees.

More of the same this period with small surf from SE and SW. Trade windswell from the southern hemisphere is expected to hold into the long range.

A low pressure system in the Tasman Sea 9/15-16 had gales over a compact area west of New Zealand. With the smaller source size and the shadowing by islands of the SW Pacific and New Zealand, slim odds for a small event locally. The PacIOOS American Samoa buoy did register low swell 9/20-21. This minor event should fill in starting late Saturday, peak late Sunday, and drop into Tuesday from 208-220 degrees.

Mid Friday on eastern shores has breakers from 60-90 degrees at levels just below the trade windswell average. Heights should slowly decline on Saturday.

See the latest NWS State Forecast Discussion for an explanation of the weather features driving the local winds.

ASCAT satellite starting 9/20 showed a large area to the immediate E to NE of Hawaii with light to gentle breezes. It is associated with an upper level low pressure system that has created a weak inverted trough near 150W. On the east side of the trough beyond 800 nm starting 9/20, there have been ribbons of fresh to strong trades aimed at Hawaii. This upstream source could keep low windswell locally out of 45-90 degrees for the weekend with a downward trend.

Windswell should be at a minimum Monday to Wednesday.

Mid Friday on northern shores has breakers from 310-325 degrees at levels below the September average. Similar size is likely for Saturday.

Two low centers associated with an upper level trough near the Dateline formed 9/19. Both were sub-gale. They should keep similar short-period surf over the weekend.

One was near 35N, 175W 9/19 with fresh to strong breezes, and pockets to near gale to near 1200 nm away. The low center moved NNE 9/20-21 and weakened.

NOAA NW Hawaii buoys show an increase late morning in the 10-12 second band. This mild reinforcement should keep surf about the same for Saturday out of 310-325 degrees.

The second low center 9/19 was just south of the Aleutians. It was stronger but aimed more north to south with weaker winds aimed at Hawaii. The fetch was broad and stretched to near 1500 nm away. It held about the same into 9/21 then weakened rapidly.

Small surf from 315-330 degrees should pick up Sunday and drop on Monday.

A zonal jet stream in the north central Pacific is steering a weak low pressure slowly eastward along 40N. It is expected to cross the Dateline late Friday and sit north of Hawaii Monday. Central pressure is not expected to drop below 1000 mb. The fresh to strong breezes with small pockets of near gales could make for similar shorter-period surf building Tuesday and holding Wednesday from 310-330 degrees.

Into the long range, models show a stronger low occluding near 35N, 170W 9/28-29, that could trend the NW to NNW surf up for the weekend of 10/1. It is too early for size specifics.

Trade windswell should remain below average 9/28-30.

Southern shores should remain at a seasonal minimum 9/28-30.

Long range forecasts are subject to low confidence.

This collaborative forecast will resume on Monday, September 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

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

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