957 
FXHW52 PHFO 140106
SRDHFO

Collaborative Nearshore Swell and Wind Forecast for Oahu
NWS/NCEI Honolulu HI
306 PM HST Mon Jan 13 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        3  NW    14     4     6  DOWN         22-27   E     SAME
01/13      12  ENE   11     8    12  SAME

TUE        11  ENE   11     8    10  DOWN   MED   19-23   E     DOWN
01/14

WED        10  ENE   10     7     9  DOWN   LOW   17-21   E     DOWN
01/15

THU         7  ENE    9     4     6  DOWN   LOW   11-16   E     DOWN
01/16

FRI         5  E      8     3     5  DOWN   LOW   13-19   NE    UP  
01/17

SAT         5  NNW   10     6     8  UP     LOW   17-21   ENE   UP  
01/18       7  ENE    7     2     4  UP     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... Winter minimum for northern shores with east side
remain above average into Thursday.

DETAILED...
Mid Monday on northern shores has breakers from 300-320 degrees at
levels below the seasonal average. Heights should be near the
seasonal minimum on Tuesday.

A blocking ridge of high pressure holds over most of the central N
Pacific. This has surface pressures much higher than normal for
most of the northern basin. It spells a void of WNW to NNW long-
period surf this week.

Strong to near gale breezes behind a SE advancing front NNW to N
of Hawaii 1/16-17 could bring a windswell from 330-360 degrees
locally on Saturday. Heights should remain well below average and
be short-lived.

Mid Monday on eastern shores has breakers from 60-95 degrees well
above the trade windswell average. More of the same is predicted
for Tuesday.

See the latest NWS State Forecast Discussion for details on the
weather pattern driving the trend in local winds and skies.

Strong to near gale breezes are modelled to slowly trend down
1/13-14 into the fresh to strong bracket for the upstream trade
windswell source within 600 nm of Hawaii. This should keep rough breakers
above average through Wednesday with a slow downward trend. With 
the short upstream fetch, the local windswell is predicted to fall
off steadily Thursday 1/16 down to levels near average by Friday 
from 60-90 degrees and below average Saturday.

A new surface high pressure system is modelled to become
established NNW of Hawaii by Friday into Saturday 1/17-18, which
should slowly trend up the windswell from 30-70 degrees. More
northern exposures should have higher windswell 1/18
aforementioned.

No long-period swell surpassing 1 feet is expected from the 
southern hemisphere this period. Most spots should hold near nil 
with high refraction zones at tiny to small with inconsistent sets 
from 140-220 degrees. Refracting easterly windswell should affect
select exposures into Thursday.

Into the long range, southern shores are predicted to hold at the
seasonal average of near nil 1/19-22.

In the north Pacific, a severe gale in the Kamchatka corner 2400
nm away 1/14-15 should trend longer period swell up Sunday 1/19
from 320-330 degrees to near the average. A system closer near the
Date Line at 45N 1/16-17 should bring surf up another notch from
330-340 degrees 1/20. In general, a return to more normal,
elevated surf conditions are expected from WNW to NNW 1/20-24.

Eastern shores should be near average 1/19 then trend below
average 1/20-22.

Long range forecasts are subject to major revisions.

This collaborative forecast will resume on Wednesday, January 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