879
FXHW60 PHFO 300659
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
859 PM HST Wed May 29 2024

.SYNOPSIS...
A high far northeast of the state will drive breezy to locally
windy trade winds through the remainder of the week. Showers will
favor windward areas, becoming more prevalent at night. Upper
troughing will move over the islands Friday into early next week,
setting up periods of increased trade showers coverage and
intensity.

&&

.DISCUSSION...
Surface troughing west of the main Hawaiian Islands, combined with
high pressure far to the northeast, has set up a pressure gradient
sufficiently steep to support moderate to breezy trade winds
across local waters this evening. Afternoon soundings show our
airmass is seasonally moist, with 1.3 to 1.5 inches of PW. Slight
instability is noted along with subsidence inversions near 6000
feet. Radar shows isolated to scattered light showers within trade
flow, embedded within patchy broken low clouds across windward
areas depicted in satellite loops.

Models show high pressure to our northeast will strengthen a bit
and drift south-southeast as troughing to our west slowly lifts
northward. This will provide a minor uptick in wind speeds into
the weekend. The trough will wash out through the weekend as high
pressure northeast of the state inches a bit southwestward and
closer to the islands early to mid next week, providing another
slight boost to trades for the first few days of June. Models also
show upper troughing will drift south across the islands next
week, possibly increasing trade wind shower coverage and
intensity.

&&

.AVIATION...
Moderate to breezy easterly trades will continue for the next
several days. Clouds and showers will favor windward slopes,
where periods of MVFR conditions will move through especially in
the overnight and early morning hours...with the occasional spill
over to leeward areas on the smaller islands. VFR conditions will
generally prevail over most leeward areas, with the exception of
afternoon and evening MVFR conditions over leeward Big Island.

A weak mid-level ridge will maintain stable conditions with an
inversion based between 6,000 to 8,000 ft. Easterly trade winds
at and below the inversion level will remain in the 15 to 20 kt
range, which will produce some low-level turbulence. It appears
that AIRMET Tango will not be needed for these borderline
conditions. However, model cross sections show 20 to 25 kts under
the inversion over the central part of the state tomorrow
afternoon, which may be enough to produce some moderate low-level
turbulence.

&&

.MARINE...
A trough northwest and a high centered far northeast of the area
will maintain moderate to locally strong easterly trade winds
through tonight. As the trough weakens and drifts further away,
the trade winds will slightly strengthen Thursday into Friday and
back towards the east-northeast. Fresh to strong east- northeast
trade winds should persist through the weekend as a ridge of high
pressure remains anchored far north of the state. A Small Craft
Advisory (SCA) remains in effect for majority of the waters around
Maui County and the Big Island through Friday and additional
zones around Oahu and Kauai waters will likely need to be included
by Friday.

Surf along exposed south-facing shores will remain small through
Friday. A series of south swells will bring a prolonged period of
above average surf along south facing shores through the start of
June. Forerunners from the first swell could arrive as early as
Friday, build and peak late Saturday into Sunday. A reinforcing
pulse should arrive on Monday and will likely maintain surf
heights near or just below the High Surf Advisory threshold of 10
feet. Surf heights should gradually trend down Tuesday through
Wednesday as the south- southwest (200 degree) swell declines. A
gale low currently developing just east of New Zealand, will
likely bring another south (190 degree) swell Thursday into Friday
of next week.

Surf along exposed east-facing shores will continue to remain
rough and choppy due to the windswell generated by the breezy
trade winds. As the trades slightly strengthen Thursday into the
weekend, we should see a slight increase of rough and choppy surf
by this weekend.

Surf along north-facing shores will continue to remain nearly flat
over the next few days. A developing storm force low near Kamchatka
should produce an out of season northwest swell, which should
steadily fill in Sunday night into Monday. Latest guidance is
showing 3 to 4 feet of swell from 320 degrees Monday into Tuesday.
A typhoon tracking off the coast of Japan will likely bring a
small reinforcing swell from the west-northwest to northwest
Tuesday into the middle of next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Friday for Kaiwi Channel-
Maui County Windward Waters-Maalaea Bay-Pailolo Channel-
Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters.

&&

$$

DISCUSSION...Powell
AVIATION...Farris
MARINE...Shigesato