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SRFHFO

SURF ZONE FORECAST
NATIONAL WEATHER SERVICE HONOLULU HI
531 AM HST MON MAY 21 2018

OAHU-
531 AM HST MON MAY 21 2018

Surf along north facing shores will be 2 to 4 feet through Tuesday.

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

Surf along east facing shores will be 3 to 5 feet today, lowering to 2 to 4 feet Tuesday.

Surf along south facing shores will be 3 to 5 feet this morning, lowering to 2 to 4 feet this afternoon through Tuesday.

Outlook through Monday May 28: Surf along east facing shores will remain rough through the week. A new south swell is expected for the second half of the week. A small northwest swell is possible Wednesday.

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
305 PM HST FRI MAY 18 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
05/18
4NNW1268SAME17-21EUP
6E613UP
2S1323DOWN
SAT
05/19
3NNW1146DOWNMED19-23EUP
8E746UPMED
2SSW1946UPLOW
SUN
05/20
2N1013DOWNLOW17-21EDOWN
8E857DOWNLOW
2SSW1746SAMELOW
MON
05/21
2NW1223UPLOW13-19EDOWN
6E835DOWNLOW
2SSW1524DOWNLOW
TUE
05/22
2NNW1013DOWNLOW13-19NEUP
6ENE724DOWNLOW
2S1323DOWNLOW
WED
05/23
3NNW1146UPLOW17-21NEUP
7NE735UPLOW
1SW2024UPLOW

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:. Spring conditions.

DETAILED:. Mid Friday on northern shores has breakers from 325-355 degrees at levels above the May average. Heights are expected to drop near the average on Saturday.

A long fetch of strong to near gale winds north of 35N to north of Hawaii 5/15-16 generated the shorter-period swell that arrived Friday morning 5/18. Drifting NOAA buoy 51101 to the NNE of Oahu suggests the peak of the energy in the 11-13 second band passed by in the early morning 5/18. The PacIOOS/CDIP Waimea, Oahu buoy 5/18 was still rising late morning in the 10-14 second band. This event will likely peak on Oahu Friday PM.

The tail of the fetch was near the Aleutians 5/16. This should keep some shorter-period wave energy through the weekend with a slow downward trend below average by Saturday night.

The jet stream over the western to central north Pacific this week has been zonal, or west to east, with embedded short-wave troughs, which in turn are associated with weak low pressure systems and fronts. The centers of low pressure are well north near the Aleutians. Zonal patterns zip the systems eastward. With marginal strength, long distance, and fast track, most events are likely average or less.

This series of of surface low pressure systems formed off the Kuril Islands with gales, but weakened rapidly as they moved east. Wave Watch III brought in swell to Oahu 5/17 from one such source, but it was lower than expected. The next series are subject to the same limitations given the remote source beyond 2500 nm.

Better odds from these sources from the weak low pressure once east of the Date Line. The fresh to strong breezes should bring in shorter-period events. The next one due is Monday and another Wednesday, both from within 320-350 degrees. Models suggest the latter to be larger.

Mid Friday on eastern shores has choppy breakers at levels below the trade windswell average. An increase is predicted for Saturday.

A zonal axis of high pressure stretches across the breadth of the central north Pacific near 30N. Models keep it in place through the weekend. ASCAT morning satellite 5/18 showed fresh trades with small pockets to strong E to ENE of Oahu out 800 nm. The long fetch should bring up the dominant wave period of the windswell by Saturday as breakers climb above average from 70-90 degrees.

The next mid latitude trough well north of Hawaii is modelled to pass east of the longitude of Hawaii 5/21-22. This should lower trades a notch locally at this time. In turn, breakers from windswell should decline Sunday to Tuesday from 70-90 degrees to levels below average.

A new high pressure center is modelled NNW of Hawaii 5/22-23, that should add more NE-component to the local winds and upstream fetch of trades, and in turn, the dominant windswell direction should back on the compass to near 60 degrees by 5/23 as it builds back to average levels.

Mid Friday on southern shores has background level surf. An increase is due on Saturday.

A pair of austral winter-caliber low pressure systems tracked SW to SE of New Zealand within 5/10-13. Both were fast-moving with ocean surface winds mostly zonal. Angular spreading should bring in swell locally.

The slow onset is expected locally late Friday into Saturday. It should be filled in by late Saturday with inconsistent sets above average, peak on Sunday with more consistent sets, then slowly drop back to background levels by Tuesday, all of the above centered from 190 degrees and spread within 180-220 degrees.

Into the long range, jet level troughs favor the longitude of New Zealand with a series of winter-caliber surface low pressures spaced about a day apart in the southern Tasman Sea and south of New Zealand. As the systems move east of New Zealand, the fetch is modelled to become too zonal. With the shadowing by SW Pacific Islands and New Zealand, this leaves Hawaii with most likely peak days near the average and other days at background levels within 5/23-28 out of 180-220 degrees centered near 210 degrees.

In the northern hemisphere, more weak sources near the Aleutians could bring in tiny to small NNW breakers for top days and lower days near flat within 5/24-28.

Trade windswell from 50-70 degrees should decrease 5/25-26.

Long range forecasts are subject to high uncertainty.

This collaborative forecast will resume on Monday, May 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 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