Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 05/21/2026 05:04:00 AM UTC

                        
144
FXHW60 PHFO 201904
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
904 AM HST Wed May 20 2026

.SYNOPSIS...
Trade winds will steadily strengthen through Thursday and could
produce advisory level winds by Thursday afternoon, especially
over Maui County and the Big Island. Passing showers will continue
to ride in with the breezy to windy trade winds through early
next week, primarily during the nights and early morning hours
across windward and mauka areas.

&&

.SHORT TERM UPDATE...
Trade wind showers were seen in the usual locations this morning,
meaning mainly windward and mauka, with precipitation amounts
ranging from a few hundredths up to around 3/4 of an inch in some
higher elevations. Skies were partly to mostly cloudy. Today
should play out like a typical trade wind day, with a slight
increase of winds as the day progresses. This is well-handled by
the current forecast and no changes are planned at this time.

&&

.PREV DISCUSSION...
Issued at 343 AM HST Wed May 20 2026
This morning`s radar and satellite imagery shows scattered showers
riding in with the breezy trade winds mainly over windward and
mauka areas. As we go through the day today and into tonight,
trade winds will steadily strengthen and a drier air mass will
move over the state. With the drier air mass in place by Thursday,
showers will remain on the lighter side, but we should continue to
see scattered showers over windward and mauka areas.

As the drier air mass moves in on Thursday, the inversion will
lower and strengthen, which will result in some gusty winds over
and lee side of terrain. Winds are expected to reach advisory
thresholds on Thursday for the windier areas around Maui County
and the Big Island, where gusts of up to 50 mph will be possible.
For Oahu, wind gusts should be slightly weaker but gusts of at
least 40 mph should be expected for areas downwind of terrain by
late Thursday.

For the weekend, windy conditions will likely continue through
Saturday. Trade winds could drop a notch on Sunday, but
nonetheless breezy to strong trades will likely continue through
early next week. Passing showers will continue to ride in with the
strong trades from time to time and will mainly be focused over
windward and mauka areas.

&&

.AVIATION...
Fresh to strong trades will increase over the next 24 hours,
becoming locally windy by Thursday as the atmosphere stabilizes.
AIRMET Sierra is in effect for mountain obscuration across most
windward areas due to MVFR conditions produced by a narrow band
of showers moving across the state this morning. Expect
improvement this afternoon. AIRMET Tango is in place for low level
turbulence over and downwind of terrain. With winds building and
stability increasing, this AIRMET will remain in place for at
least the next couple of days.


&&

.MARINE...

The high pressure ridge north of the Hawaiian Islands will
strengthen over the next few days, resulting in trade winds
increasing into the strong to gale range from Thursday into early
Friday morning. A Gale Watch remains in effect for the Alenuihaha
and Pailolo Channels. A Small Craft Advisory (SCA) remains in
effect and will expand to all island waters by Thursday. Expect
SCA to continue into the first half of next week.

Small, short- to medium-period north-northwest (330 degree) swell
energy will decline through Thursday. The next small north-
northwest (330 degree) swell will move into the Hawaii region on
Saturday increasing surf heights along north- and west-facing
shores through the weekend.

A series of small, long-period south swell energy supports near-
average surf along south-facing shores over the next seven days.
Meanwhile, strengthening trades maintain elevated surf along
east-facing shores into next week.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory from 6 PM this evening to 6 AM HST Friday
for Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-
Kauai Windward Waters-Oahu Windward Waters.

Small Craft Advisory until 6 AM HST Friday for Big Island
Leeward Waters-Big Island Southeast Waters-Big Island Windward
Waters-Kaiwi Channel-Maalaea Bay-Maui County Leeward Waters-Maui
County Windward Waters-Oahu Leeward Waters.

Small Craft Advisory until 6 AM HST Thursday for Alenuihaha
Channel-Pailolo Channel.

Gale Watch from Thursday morning through late Thursday night for
Alenuihaha Channel-Pailolo Channel.


&&

$$

DISCUSSION...Kino
AVIATION...Wroe
MARINE...Farris