Surf Discussion
Issued by NWS Honolulu, HI

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817
FXHW52 PHFO 120044
SRDHFO

Collaborative Nearshore Swell and Wind Forecast for Oahu
NWS/NCEI Honolulu HI
244 PM HST Fri Oct 11 2019

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        5  E      7     2     4  SAME           4-6   VRB   SAME
10/11       2  SSW   13     2     4  SAME

SAT         2  NNW   11     2     4  UP     LOW   17-21   E     UP
10/12       6  E      7     3     4  UP     LOW
            1  SSW   20     2     5  UP     LOW

SUN         2  NNW   10     1     3  DOWN   LOW   17-21   E     SAME
10/13       6  E      8     3     5  SAME   LOW
            2  SSW   16     3     5  UP     LOW

MON         5  E      8     3     4  DOWN   LOW   13-19   E     DOWN
10/14       2  S     14     3     4  DOWN   LOW
            2  W     17     3     5  UP     LOW

TUE         5  E      8     3     4  SAME   LOW   11-16   NE    SAME
10/15       2  S     14     3     4  UP     LOW
            2  W     15     3     5  SAME   LOW

WED         5  ENE    7     2     4  DOWN   LOW   11-16   NE    SAME
10/16       2  S     14     3     4  SAME   LOW
            2  W     14     3     4  DOWN   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...
Low spell holding.

DETAILED...
Mid Friday on northern shores has breakers at summer levels of
near nil. Heights should remain well below the seasonal average on
Saturday.

Strong breezes aimed west of Hawaii from north of 40N along 160W
10/9-10 could give tiny to small breakers from 325-345 degrees
Saturday into Sunday.

The primary north Pacific jet remains in summer mode well north
and of weaker strength in a zonal pattern that is leading to the
slow start of the Fall surf season.

Mid Friday on eastern shores has breakers from 70-100 degrees at
levels a notch under the trade windswell average. A slight
increase is possible for Saturday.

Surface high pressure 10/11 of 1025 mb near 35N, 145W has a large
area of fresh trades with pockets to strong from near 140-155W
within 20-22N. Models show fresh easterly trades filling into Oahu
late Friday into Saturday. This should lead to a notch greater
surf into Saturday from the upstream and local trades. Heights
should peak on Sunday near the trade windswell average.

Models show the upstream trades holding into Sunday 10/13 then
dropping sharply. This should keep active breakers from windswell
from 70-90 degrees into Tuesday. It should drop well below average
by Wednesday 10/16.

Mid Friday on southern shores has breakers from 180-210 degrees at
levels within background to average. Surf should continue similar
on Saturday with an upward trend.

A storm-force system tracked rapidly east along 60S to the S to SE
of New Zealand 10/4-6. Seas over a wide fetch grew above 30 feet
with aim at the Americas. Angular spreading should bring in surf
locally.

The onset stage is Saturday 10/12 with inconsistent sets out of
180-200 degrees. The event should be filled in and peak on Sunday
10/13, then slowly drop into Monday 10/14 from the same
direction.

A compact gale due south of Hawaii near 35S 10/7 tracked southward
as it intensified. The track away from Hawaii reduces the fetch
length and duration. It should be enough to keep surf within
background to average Tuesday into Wednesday 10/15-16 out of
170-185 degrees.

Mid Friday on western shores has below average surf. Similar
conditions are predicted for Saturday.

Super typhoon Hagibis began tracking north from 20N, 140E 10/9-10.
Low, long-period swell from 270-290 degrees is expected locally
starting Monday 10/14 for westerly exposures. Shadowing by Niihau
and Kauai add greater error bars to the surf height estimate. The
event should hold into Wednesday 10/16.

Into the long range, Hagibis is modelled to become extratropical
near Hokkaido, Japan 10/12-13, then get caught in the north
Pacific zonal jet stream and race rapidly towards the Gulf of
Alaska. The fast track from the 300 to 360 great circle rays to
Hawaii limits fetch duration and lowers surf potential. Wave Watch
III estimates based on the GFS model show only 2` deep water,
long-period swell for late Wednesday to Friday centered from 310
degrees. The European model suggests slightly more. In general,
the event is expected to be below the October average.

Trade windswell is predicted to be average or less 10/17-19.

In the southern hemisphere, a storm-force system at 60S, 170W
10/11 is moving rapidly east. It could bring low, long-period S
swell locally for the weekend of 10/19-20.

Long range forecasts are subject to major revisions.

This collaborative forecast will resume on Tuesday, October 15.

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



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