Surf Discussion
Issued by NWS Honolulu, HI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3
000
FXHW52 PHFO 270057
SRDHFO

Collaborative Nearshore Swell and Wind Forecast for Oahu
NWS/NCEI Honolulu HI
257 PM HST Tue May 26 2020

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

FORECAST  SWL  DMNT DMNT  H    H     HGT          WIND   WIND   SPD
DATE      HGT  DIR  PD    1/3  1/10  TEND   PROB  SPD    DIR    TEND
1 PM        2  NNW   11     3     4  DOWN          8-12     E   SAME
05/26       2  SSE   13     3     5  SAME
            2  SSW   15     3     5  SAME

WED         3  NNW   11     4     6    UP   LOW    9-14     E     UP
05/27       2  SSE   13     3     5  DOWN   LOW
            2  SSW   13     3     5  DOWN   LOW

THU         3  NNW   10     3     5  DOWN   LOW   11-16   ENE     UP
05/28       2  SSE   12     2     4  DOWN   LOW
            1   SW   20     3     4    UP   LOW

FRI         2  NNW   10     1     3  DOWN   LOW   11-16   ENE   SAME
05/29       2  SSW   17     3     5    UP   LOW

SAT         3  NNE   13     4     6    UP   LOW   11-16   ENE   SAME
05/30       2  SSW   16     3     5  SAME   LOW
            2  SSE   11     3     4    UP   LOW

SUN         3  NNE   11     3     5  DOWN   LOW   11-16   ENE   SAME
05/31       2  SSW   14     3     5  DOWN   LOW
            2  SSE   11     3     4  SAME   LOW


LEGEND:
SWL HGT    Open ocean swell height measured from trough to crest
           in feet located 20 nautical miles offshore
DMNT DIR   Dominant direction typically +/-10 degrees in 16 compass
           points
DMNT PD    Dominant period in seconds
H1/3       Significant wave height in the surf zone
H1/10      Average height in the highest one-tenth waves in the surf
           zone
HGT TEND   Height tendency of swell (valid values: UP/DOWN/SAME)
PROB       Probability of occurrence (valid values: HIGH/MED/LOW)
WIND SPD   Open water wind speed measured in knots located
           20 nautical miles offshore
WIND DIR   Wind direction in 16 compass points
SPD TEND   Wind speed tendency (valid values: UP/DOWN/SAME)

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

DISCUSSION:
SUMMARY...Surf from N and S to continue at typical seasonal size.

DETAILED...
Mid Tuesday on northern shores has declining breakers from 320-340
degrees at levels below the May average. The present event is
predicted to fade into Wednesday as a new episode fills in mid
Wednesday.

The N Pacific has had an active cyclonic pattern for April and May
giving an overall above average surf pattern for Hawaii out of WNW to
NNE.  Another unfolding low pressure pattern is on tap to finish off
the month with more surf near average.

A compact, fast-moving low pressure formed NNW of Hawaii 5/25 and is
tracking NE as it intensifies. JASON altimeter showed seas within
10-15 feet within 32-28N to the immediate NNW of Hawaii Monday night.
With the head of the fetch over the 315-330 degree band within 900
nm, proximity should give Hawaii a small NW to NNW event building mid
day Wednesday with 10-14s wave periods, peaking Wednesday night, and
dropping Thursday.

The models show the fast-moving system reaching near 50N, 145W in the
Gulf of Alaska by Wednesday 5/27. During the tracking phase away from
Hawaii, generation of seas and swell towards Hawaii was limited. This
should result in a minimum for this event on Friday 5/29 locally. But
models show the center remaining stationary 5/27-29 allowing time to
generate swell towards Hawaii. It is expected to have a weakening
trend with the head of the fetch about 1800 nm away. Thus, only a
small event is likely. It should trend upward with moderate period
surf of 12-15s from 000-020 degrees Saturday morning 5/30, peaking
Saturday night, then dropping Sunday.

Mid Tuesday on eastern shores has breakers from 30-90 degrees near an
east side minimum.  Low conditions should hold on Wednesday.

See the latest NWS State Forecast Discussion regarding the increasing
trade wind pattern mid week.

The new trade wind event is expected to have too low of magnitude and
too short of fetch to bring surf from wind swell out of 40-90 degrees
beyond low-end, east side levels. The aforementioned NNE event for
the weekend of May 30-31 should top the heights for more northerly
exposures.

Mid Tuesday on southern shores has steady breakers near the summer
average from a mix of SSE and SSW sources.  Heights are expected to
hold about the same into Wednesday 5/29 with a slow downward trend.

The SSE component from 150-170 degrees arriving 5/26 was generated by
a compact gale in the subtropics south of French Polynesia 5/18-20.
It tracked slowly east along 35S.  This event should last a few days
at levels near to a notch below the summer average.


The SSW component arriving 5/26 was from a low pressure with zonal
surface winds, or west to east, south of 55S, aimed seas over 40 feet
at the Americas 5/16-17.  This event had a long-lived spell of
long-period swell giving near to a notch over average surf during the
long weekend locally. Southern Hawaii NOAA buoys still show energy in
the 12-16s band into midday 5/26. This event should slowly trend down
Wednesday into Thursday.

Another strong austral low pressure system with central pressure
below 950 mb tracked east along 60S 5/20-22. It filled the southern
Tasman Sea with seas over 30 feet 5/20. Long period swell from this
direction should have slow onset locally starting Thursday 5/28 from
208-220 degrees. This component be filled in by Friday and drop on
Saturday.

Seas over 35 feet were just S to SE of New Zealand 5/21-22. This
portion has better odds for reaching Hawaii. Seas were lower than the
source that gave the Memorial day weekend swell locally but the new
source was about 600 nm closer. The new source forerunner,
long-period swell trains have rolled under the PacIOOS/CDIP American
Samoa buoy 5/25-26. It shows energy levels in the 18-22s band similar
to a notch under the first event. This suggest another long-period
event locally with onset Friday 5/29, filled in by 5/30, then holding
about the same near average into Sunday from 180-200 degrees.

Strong trades east of the Tuamotu Islands 5/23-26 could add some
southern hemisphere wind swell of 10-12s out of 140-160 degrees
locally starting Saturday 5/30. It should last about 4 days.

Into the long range, at the jet stream level, a mid-latitude,
long-wave pattern has set up with the ridge near New Zealand and a
trough south of French Polynesia. A severe-gale to storm-force system
is modelled to set up a captured fetch at the eastern edge of the
Hawaii 5/26-28. Wave models show Hawaii within aim of the high seas
over 30 feet. This suggests above average surf locally with onset
within mid Monday 6/1 to mid Tuesday 6/2. It should be filled in late
6/2 above average, peak Wednesday 6/3 potentially well above average
from 175-190 degrees, then slowly drop into 6/5.

In the north Pacific, models show a marginal gale tracking east from
the Kuril Islands 5/28 along the Aleutians reaching the Date Line
5/30. This could give a small NW to NNW event locally within 6/3-4.
East side is modelled to slowly increase within 6/1-3 though remain
below average from 40-90 degrees.

Long range forecasts are subject to major revisions.

The next Collaborative Forecast will be updated Friday, May 29.


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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.