592
FXHW60 PHFO 302010
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
1010 AM HST Thu May 30 2024

.SYNOPSIS...
Surface high pressure far northeast of the islands will remain the
impetus to breezy and locally windy trade winds. Drier weather
will prevail the next couple of days. Isolated showers will favor
windward areas and become more prevalent at night. Upper troughing
to the northeast of the state will move over the area from Friday
through the weekend. This will create a more unstable scenario
and, with increasing moisture through the middle of next week,
trade shower coverage and intensity will likely be on the rise.


&&

.DISCUSSION...
A 1031 mb surface high is centered approximately 1,400 miles
northeast of Oahu in tandem with surface troughing located about
1,100 miles from Kauai. This is producing a tight enough pressure
gradient back across the island chain to maintain breezy to
locally windy trade winds. A drier air mass is advecting in from
the east as evidenced in this morning`s local sounding pwats in
the 1.1 to 1.3 inch range. A dry 850-700 mb layer, along with a
stout near 5k ft inversion, will guarantee just isolated shower
activity through Friday. Precipitation that does develop within
the shallow boundary layer will be isolated in coverage and
produce measurable accumulations of no more than a few tenths of
an inch along windward-facing mauka slopes and coastlines. Mainly
clear to partly cloudy/broken low cloud skies at lower elevations
that will warm into the lower 80s (mid 60s to lower 70s at 6k ft
elevation) will be the general rule both today and tomorrow.

High pressure northeast of the state will settle more south-
southeast as the trough of low pressure west of the area slowly
lifts northward and washes out the next couple of days. This will
hold a tight pressure gradient across the region this weekend to
maintain or slightly boost breezy to locally windy (in gust)
trades. Heights will lower over the state from Friday into the
weekend. Extended NWP guidance is still a little out of phase on
the location of this troughing. The EC solution keeps upper
troughing out west as upper ridging builds in from east. This
would equate to an uneventful, but slightly more wet, trade wind
weather regime. The more bullish GFS is keeping the upper
low/weakness over the islands longer and this would result in a
more longer duration wet trade wind pattern. The emergence of the
subtropical jet over or just south of the islands this weekend
may offer more argument to a wetter early June pattern, all
dependent on its positioning. Mid levels will remain fairly dry
until Tuesday so this may weigh the forecast toward more dry.
Regardless of any these minor model nuances, there is moderate
confidence that next week`s upper troughing scenario will increase
areal shower coverage and intensity...especially going into the
middle of next week due to higher lower to mid layer moisture.


&&

.AVIATION...
Moderate to breezy trades will slightly strengthen this afternoon
and remain breezy over the next several days. Mostly dry conditions
this morning will give way to an increase of showers over the Big
Island and windward Maui this afternoon and rest of the state
tonight. Clouds and showers will favor windward slopes with brief
MVFR conditions possible with the showers. VFR conditions will
generally prevail across leeward areas.

Soundings show a strong inversion between 5000 and 6000 ft. With
the trades picking up a touch this afternoon, light to moderate
low level turbulence will be possible south through west of any
terrain. AIRMET TANGO will likely be needed this afternoon. Also
with the increase of showers over the eastern half of the state
this afternoon, AIRMET SIERRA may also be needed. With the showers
expanding toward the rest of the state tonight, AIRMET SIERRA will
be possible for other windward areas tonight.


&&

.MARINE...
High pressure centered far northeast of the area will maintain
moderate to locally strong east-northeast trade winds today.
Winds will strengthen slightly to fresh to locally strong Friday
through the weekend as the high drifts south, tightening the
gradient. The Small Craft Advisory for waters around Maui County
and the Big Island has been trimmed back to just the typical windy
waters into Friday. Additional zones around Oahu and Kauai waters
will likely need to be included late Friday as winds strengthen.

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 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
and will likely increase slightly by this weekend.

Surf along north-facing shores will continue to remain nearly flat
over the next few days. A storm force low near Kamchatka should
produce an out of season northwest swell that is expected to fill
in late Sunday night into Monday. Latest guidance is showing 3 to
4 feet of swell from 320 degrees Monday into Tuesday. A small
tropical storm tracking off the coast of Japan will transition
into a broad extra tropical gale as it tracks north then eastward
over the next couple of days. This system could 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 Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.


&&

$$


DISCUSSION...Blood
AVIATION...Kino
MARINE...Almanza