043
FXHW60 PHFO 300132
AFDHFO

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

.SYNOPSIS...
Surface high pressure far northeast of the state will maintain
breezy to locally windy trade winds for the remainder of the
week. Occasional shower activity will primarily be focused along
windward slopes and coastlines, becoming more prevalent during the
nocturnal hours. Upper level troughing northeast of the region will
move over the islands from Friday into early next week. This set
up will likely produce more frequent periods of increased trade
showers in both coverage and intensity.


&&

.DISCUSSION...
A weak low within surface troughing are located approximately 700
nautical miles west-northwest of Kauai, along with a near 1034 mb
surface high centered about 1,300 nautical miles northeast of
Oahu. These are supporting a breezy to locally strong regional
trade wind regime. The regional atmosphere was fairly moist with
morning sounding pwats between 1.4 to 1.6 inches pushing the
upper percentile of the late May climatological range. This
relatively higher moisture within this breezy trade flow is mainly
producing mainly scattered to broken mid level clouds, with
occasional overcast windward mauka conditions, within a warmed
inland air mass in the lower 80s. A quiet afternoon radar-wise
with just isolated spotty showers. Other than Mt. Waialeale`s half
of an inch today, the highest six hour rainfall of just a couple
of tenths of an inch have been confined to the higher windward
elevations. Better organized, deeper showers may drift over into
the smaller island leeward communities. The main short to mid term
forecast theme will center around daily rain chances and trade
wind trends.

A relatively mid to upper level drier air mass will travel across
the state from the northeast through the weekend. This scenario
will create a shallow near 5k ft inversion that will produce
light windward slope and coastal showers that will become more
frequent overnight. High pressure will slightly strengthen
northeast of the state and settle more south-southeast as the
trough of low pressure west of the area slowly lifts northward the
next couple of days. This will provide a minor uptick of wind
magnitudes as winds remain breezy to locally windy into early
June. The trough will wash out through the weekend as high
pressure northeast of the state inches a bit southwestward and
closer to the island chain early to mid next week. This may
provide a slight boost to trades the first few days of June.

Heights will lower over the state from Friday into the weekend
although extended NWP guidance is a little out of phase on the
location of this troughing. The EC solution keeps upper troughing
out west, upper ridging building in from east = basic trade wind
weather pattern. The GFS is more bullish in keeping the upper
low/weakness over the islands longer = more wet trade wind
pattern. Regardless of these minor model nuances, there is
moderate confidence that next week`s upper troughing scenario will
increase areal shower coverage and intensity as lower to mid
layer relative humidity increases over the state.


&&

.AVIATION...
Moderate to breezy easterly trades will continue for the next
several days. Clouds and showers will favor wind ward slopes,
where periods of MVFR CIGs/VSBYs will move through especially in
the overnight and early morning hours. VFR conditions will
prevail over most leeward areas, with the exception of afternoon
and evening MVFR conditions over leeward Big Island.

A 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, though we will continue to monitor.


&&

.MARINE...
A trough northwest of the area 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 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 below the
summer average (5 feet) through Friday. A series of south swells
will move in over the weekend into next week and will likely bring
a prolonged period of above average surf along south facing
shores. Forerunners from the first swell could arrive as early as
Friday, but should steadily fill in throughout the day Saturday
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...Blood
AVIATION...Wroe
MARINE...Kino