442
FXHW60 PHFO 241303
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
303 AM HST Sat May 24 2025

.SYNOPSIS...
High pressure far to our northwest will keep breezy trades blowing
through Sunday, with the trades gradually easing next week as the
high weakens. An upper low moving to the northeast away from the
islands over the holiday weekend will bring drier and more stable
air to the region, with fewer showers and lots of sunshine expected.

&&

.DISCUSSION...
The forecast has been updated to reflect the latest trends,
following the National Blend of Models (NBM). That being said,
very little was changed with little change with the latest runs of
the NBM.

A relatively strong and large high pressure system remains far to
the northwest of Kauai. This high has been bringing breezy trade
winds to the region. A mid to upper level low remains about 250
miles north of Maui, and is expected to slowly move to the
northeast. Showers continue to be carried in on the trades, with
the mid to upper level low still helping to enhance some of the
showers. As the upper level feature moves further from the
islands, a more stable airmass is expected to move over the
islands. That will in turn lead to fewer showers across the
islands.

A band of moisture upstream of the islands overnight is being
carried in on the trade wind flow, but has also been being eroded
as it moves closer to the islands. While the band has been
thinning, it could still interact with the mountains to bring a
little uptick in showers over the windward sides of the islands as
it reaches the islands in a few hours.

Otherwise, a more stable airmass is expected to move over the
islands later today as the above mentioned upper level system
moves away. Lower than normal precipitable water (PW) is expected
Saturday night, with an increase in PW expected midweek. That
increase could mean an uptick in showers, however it looks like
most of that increase PW could be tied to mid to high level
moisture being drawn northward over the islands. That likely is
more indicative of increased high clouds over the islands, with
little change in the shower activity.

Trade winds should remain breezy through Sunday, then start
trending downward on Memorial Day as the high gradually shifts
south, weakens, and elongates across most of the eastern Pacific
becoming a rather weak subtropical ridge by about Wednesday or
Thursday when gentle trades are expected, staying locally breezy
only in the normal windiest spots.

&&

.AVIATION...
The upper low that had been enhancing trade wind showers near the
islands will continue to move to the northeast away from the
region this weekend. A batch of moisture just northeast of the
islands will be carried in on the trade wind flow this morning.
While this moisture area has eroded some overnight, interaction
with the mountainous terrain could bring an increase in showers,
mainly over the windward areas of the islands. No AIRMETs are
currently in effect, but AIRMET Sierra may needed for mountain
obscuration if the moisture band remains thick enough.

An overall drying trend is expected later this afternoon, with
more lighter trade wind showers expected by tomorrow. Moderate to
locally breezy trade winds will continue to persist through the
weekend.


&&

.MARINE...
High pressure off to the distant north-northwest will maintain
moderate to fresh trade winds today. A brief stint of moderate to
locally strong trades is expected tonight before the high
continues to weaken. By Monday, the ridge to the north weakens
keeping gentle to locally fresh trade winds through the first half
of next week. A Small Craft Advisory for the windier waters and
channels around Maui County and the Big Island has been cancelled
this morning and may need to be reissued this afternoon for
tonight as it may be just near the criteria tonight through early
Sunday.

A small long period south-southwest swell has begun to fill in
overnight and will peak today before gradually declining through
early next week. A similarly-sized long- period south- southwest
swell is expected to arrive next Wednesday into Thursday,
bringing another boost to south shore surf.

East shore surf will remain near seasonal average through the weekend
as trade winds persist, then gradually decline into midweek as the
trades weaken slightly. Surf along north facing shores will
remain tiny through early next week. Guidance suggest the north
Pacific getting active over the weekend, which will result in an
uptick to the surf as a small medium period north -northwest swell
is expected during the later half of next week.

Starting today and lasting into Wednesday, we can expect higher
than normal tides, which could lead to some coastal flooding
during the peak of high tides in the early afternoon hours. As
this elevated tide is expected between the aforementioned south
swells, this event will likely have minimal impact.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$


DISCUSSION...M Ballard
AVIATION...M Ballard
MARINE...Shigesato