153
FXHW60 PHFO 280148
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
348 PM HST Mon May 27 2024

.SYNOPSIS...
High pressure northeast of the state will maintain moderate to
locally breezy easterly trade winds through the week. Showers will
mainly favor windward and mauka areas, especially during the
overnight through early morning hours each day. A drier trade wind
pattern is expected during the second half of the week.

&&

.DISCUSSION...
Moderate to locally breezy trade winds continue across the
islands today with broad high pressure north of the state.
Meanwhile, a surface trough west of the islands and its attendant
low aloft are producing an area of enhanced showers and
thunderstorms that has now entered the offshore waters,
approximately 150 nm west of Kauai. The afternoon sounding at
Lihue has shown an increase of instability as the upper low
associated with the trough to the west rotates northeastward and a
weak shortwave advances towards Kauai. Elsewhere across the
state, mostly stable conditions are observed this afternoon with
scattered showers favoring windward and mauka locations. For the
Big Island, daytime surface convergence has increased clouds and
produced a few showers leeward as well. Rainfall totals have been
mostly unremarkable today, however, as most showers have been
light.

Tonight through Tuesday, a trough aloft will quickly pass in
close proximity to the western end of the state. This is expected
to bring the aforementioned area of showers and thunderstorms to
its closest point to the islands from tonight through Tuesday
night. Based on the latest guidance, isolated thunderstorms have
been introduced for the far northwest coastal waters just NW of
Niihau with this afternoon`s forecast updates. However, guidance
remains consistent in keeping this slightly too far northwest to
impact Kauai. Elsewhere, shallow moisture embedded within the
trades will produce some windward and mauka showers, especially
during the overnight through early morning period.

The low aloft west of the state will weaken as mid level ridging
and the surface high to the far northeast strengthen from
Wednesday onward. With the high remaining in place into the
weekend, expect continued locally breezy trade winds, increasing
stability, and a drier pattern during the second half of the week.

&&

.AVIATION...
Moderate to breezy trade winds will bring clouds and showers with
periodic MVFR conditions to windward and mauka areas, with better
coverage expected during the overnight to early morning hours.
Otherwise and elsewhere, VFR conditions will prevail.

With a weak shortwave trough passing just northwest of the state
and increased mid level clouds around Kauai, the potential exists
for light icing between 160 and FL250 and light to moderate
turbulence between FL200 and FL340 through tonight.

AIRMET Sierra is in effect for mountain obscuration for windward
Big Island and N through SE sections of Maui through Oahu. This
AIRMET may be needed for portions of the island chain through
tomorrow morning.

AIRMET Tango remains in effect for moderate low-level turbulence
downwind of island terrain and may be cancelled later this
evening if winds under the inversion fail to increase. Conditions
for moderate low-level turbulence look marginal through the next
couple of days and AIRMET Tango may be needed on and off through
the period.

&&

.MARINE...
Moderate to strong easterly trades will continue through the week
as the surface ridge remains positioned north of the state. The
strongest winds are expected over the windier waters around Maui
County and the Big Island, supporting the Small Craft Advisory.
The lightest winds are anticipated over the Kauai waters,
fluctuating between east and east-southeast over the next few days
due to a persistent surface trough to the west. A shift out of
the east-northeast is likely later in the week as the trough
weakens and drifts away from the region.

Surf along exposed south-facing shores will remain small
throughout much of the week, due to a combination of background
south-southwest and southeast swell energy. An upward trend is
expected from Friday through the first week of June due to an
active pattern setting up within our swell window near New
Zealand.

Altimeter and ASCAT passes over the past couple of days reflected
the potential for next weekend, showing a broad swath of gale-to
storm-force winds with seas up to 30 feet focused at the state
within the 190-200 degree directional bands. This will mark the
beginning of a long-lived event with additional reinforcements
expected within the same area over the next several days.

Surf along exposed east-facing shores will remain small and
choppy throughout the week as the trades persist.

Surf along north-facing shores will remain near the summertime
average each day, with only small background northwest pulses
expected today and potentially next weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Tuesday for Pailolo Channel-
Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters.

&&

$$

DISCUSSION...Vaughan
AVIATION...Farris
MARINE...JVC