Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 05/19/2026 11:28:00 AM UTC

                        
316
FXHW60 PHFO 190128
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
328 PM HST Mon May 18 2026

.SYNOPSIS...
An unstable and somewhat wet trade wind pattern will continue
through Tuesday night, with brief downpours possible. From
Wednesday into early next week, an area of high pressure north of
the islands will push drier air the region and strengthen winds.
The result will be a moderate to breezy trade wind pattern.

&&

.DISCUSSION...
Showers across windward and mauka areas, along with the Kona
Districts on Big Island, were noted on radar this afternoon. Some
showers have been producing moderate to briefly heavy rain, and
this has resulted in the issuance of flood advisories on Kauai and
on Big Island. These showers will trend down around sunset. Winds
were averaging 10 to 20 mph with gusts 20 to 30 mph.

Conditions remain on the humid side this afternoon as we await
drier air that should arrive from Tuesday night into Wednesday
night. Until that arrives, we will continue to see rather wet
trades, meaning we will continue to have the chance for moderate
to briefly heavy rain from showers. From late Wednesday onward, we
will see noticeably lower PW values (down around 1 inch) going
all the way into next week. Aloft, an upper level ridge will
become established to our north, even as weak troughing will
extend off the southwest coast of the mainland toward Hawaii. This
troughing will have little to no impact on our surface weather,
as the upper ridging will help keep relatively dry trades
established over the region. Dewpoints will fall several degrees
as the dry air comes in, allowing a little more cooling overnight
for wind-sheltered areas.

&&

.AVIATION...
Moderate to locally breezy trades expected hold for the next
couple days. Low cigs and SHRA will primarily impact windward and
mauka locations with some limited spillover to leeward areas. Kona
slopes of the Big Island will see low cigs and SHRA in the
afternoon with some clearing overnight. MVFR conds possible in
heavier SHRA, otherwise VFR prevails.

AIRMET Sierra is in effect for mtn obsc for windward Kauai, Oahu,
Maui and the entire area of the Big Island.

Weak inversion heights are have kept moderate low level turbulence
from developing this afternoon. Thus will hold off issuing AIRMET
TANGO, but will continue to monitor over the next day or so as
the atmosphere become more stable.

&&

.MARINE...
A surface high centered far northeast of the state will generate
moderate to locally strong trades over the next few days. This
anchored high will strengthen and expand during the second half of
the week and will cause the trade winds to strengthen to
widespread strong speeds with near gales over the windier zones
around Maui County and the Big Island. A Small Craft Advisory
(SCA) is currently in effect for the windier zones around Maui
County and the Big Island. The SCA will expand in area later this
week as the trades strengthen.

A small size, short to medium period north northwest is expected on
Tuesday. A Gale low developing in the North Pacific on Tuesday
should send a small northwest to north northwest bump over the
weekend.

A series of small long-period south-southwest swells will provide
surf near the summer average along south facing shores throughout the
week. Strengthening trades later this week will bring an increase of
short-period energy and will bring elevated surf along east
facing shores by Thursday or Friday.

Water levels peaking between 2.5 to 3.0 ft MLLW during today`s high
tides may result in some minor overwash within low lying coastal
areas this afternoon.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Wednesday for Alenuihaha
Channel-Big Island Leeward Waters-Big Island Southeast Waters-
Maalaea Bay-Pailolo Channel.


&&

$$

DISCUSSION...Parker
AVIATION...Almanza
MARINE...Kino