469
FXHW60 PHFO 260659
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
859 PM HST Tue Jun 25 2024

.SYNOPSIS...
A stable trade wind pattern will persist through much of the week
with breezy to locally windy trades. Periodic light showers will
focus over windward and mauka areas during this time. An increase
in shower activity and isolated thunderstorms will be possible
over portions of the state from Friday into the weekend as an
upper-level disturbance approaches and moves over the region.

&&

.DISCUSSION...
This afternoon, surface high pressure remains centered far north
of the main Hawaiian Islands. The 00z sounding from Hilo
continues to show a strong inversion around 4500 feet with little
moisture trapped below the inversion. This is supported by
regional satellite imagery, which shows only a few clouds over
windward areas of Maui County and the Big Island. Meanwhile, the
western end of the state has experienced a few more showers and
windward clouds today as the band of moisture that was near Kauai
this morning has continued to move through (although it is
dissipating this afternoon).

High pressure to the north is expected to weaken slightly over
the next couple of days. This should relax our local pressure
gradient a bit, but winds will still remain breezy through much
of the week. Impulses of moisture embedded in the trade wind flow
will continue to favor windward and mauka areas, though rainfall
accumulation will be limited. Aside from some brief afternoon/evening
showers over Kona slopes of the Big Island, leeward areas will
remain mostly dry.

Conditions start to change near the end of this week and into the
weekend as guidance continues to show a disturbance aloft moving
across the islands from east to west. Looking back at the past
several model runs, they have been very consistent in bringing a
low aloft near the islands on Friday, and then have it passing
over the islands from the east this weekend. This feature will
increase instability as it moves near the western end of the
state. This instability could enhance trade wind showers,
particularly on Saturday night. Isolated thunderstorms are also a
possibility, both over the western end of the island chain closer
to the upper low and over the slopes of the Big Island Friday and
Saturday afternoons. With this afternoon`s forecast updates,
thunderstorms have been added for these areas given the increasing
confidence. With that said, precipitable water values may be a
limiting factor, preventing showers and thunderstorms from
reaching their full potential. Therefore, expect further refinements
to the forecast for the Friday through Sunday period as details
become more clear this week.

&&

.AVIATION...
Breezy trade winds will persist across the island chain through
the next 24 to 48 hours. Showers and low clouds riding in on these
trades will bring brief periods of MVFR conditions over windward
and mauka locations. Otherwise, VFR conditions will prevail.

AIRMET Tango remains in effect for moderate low-level turbulence
over and downwind of island terrain due to breezy trade winds
under the tradewind inversion.

AIRMET Sierra for tempo mountain obscuration across windward
Kauai will be cancelled but may be needed again later if shower
coverage increases.

&&

.MARINE...
High pressure will remain present over the Central North Pacific
through the weekend and possibly into next week. Moderate to
locally strong easterly trades will persist through Thursday. The
high will weaken slightly toward the end of the week into the
weekend easing trades to gentle to fresh range. The Small Craft
Advisory (SCA) for the typically windier waters around Maui County
and the Big Island has been expanded through Thursday afternoon.
An upper level low may bring isolated thunderstorms which could
imply locally higher winds and seas.

Surf along east-facing shores will gradually ease through the week
as the winds locally and upstream trends down through the week.

A small, medium-period, south swell has peaked and will trend
down into Wednesday. Another small, medium- to long- period south
swell will fill in Wednesday night, peak Thursday night before
gradually easing into the weekend.

Surf along north facing shores will be minimal through tonight
into Wednesday. A small, medium period, northwest swell could
fill in late Wednesday, peaking Thursday night providing a small
bump along north facing shores through the rest of the week.

&&

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

&&

$$

DISCUSSION...Thomas
AVIATION...Shigesato/Powell
MARINE...Almanza