055
FXHW60 PHFO 141345
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
345 AM HST Sat Sep 14 2024

.SYNOPSIS...
Locally breezy trade winds will continue into next week, delivering
passing showers that will favor windward areas. Deeper moisture will
move over the islands Sunday night and Monday, likely bringing
increased shower coverage, especially over the Big Island, where
some heavy showers may develop.

&&

.DISCUSSION...
A lingering low-level trough about 700 miles NNW of the islands will
move W and finally dissipate this weekend, allowing consolidating
surface high pressure along 40N to drive breezy and locally gusty
trade winds into next week. The returning trade wind flow has been
gradually moistening the last couple of days, and radar this morning
shows scattered showers moving ashore over windward areas, with a
few small heavy rain cores noted. This gradual moistening is likely
to continue through the weekend, leading to passing showers over
windward areas occasionally bringing a few sprinkles to leeward
areas through Sunday, especially night and morning.

Model guidance indicates that a sharp 700 mb trough currently about
700 miles SE of the Big Island (from 11N to 18N along ~146W) will
move W and bring increased low- and mid-level moisture over the
islands from Sunday night through Monday. Although low-level winds
may only veer slightly to the ESE, the 700 mb flow will become
southerly as the trough passes, leading to moisture extending as
high as 12-15 kft, mainly over the Big Island. With PWAT expected to
exceed 2", the forecast includes mention of heavy showers over the
Big Island Sunday night into Monday. While the moisture increase
over the smaller islands is not expected to be as deep, an increase
in windward showers is likely, with low-level dew points in the low-
to mid-70s making it feel muggy statewide.

After the trough moves W of the islands Tuesday and Wednesday, a
fairly typical trade wind weather pattern is expected. As we
approach the end of the dry season however, we anticipate increased
interruptions to the trade wind flow as the N Pacific storm track
begins to get started. Though confidence is low, guidance has been
trending toward a solution that would lead to decreasing and veering
winds for a short period around the the end of next week, with trade
winds increasing again in about 7-8 days.

&&

.AVIATION...
Moderate to locally breezy trades expected through the weekend. SHRA
and low cigs with periods of MVFR conds should be focused over
windward and mauka areas. VFR conds should prevail elsewhere.

AIRMET Sierra is in effect for mtn obsc for windward Big Island.

&&

.MARINE...
Moderate to locally strong trades continue into next week as broad
high pressure develops over the NE Pacific. A Small Craft Advisory
(SCA) remains posted for the typical windier waters of Maui County
and the Big Island through Sunday night. The SCA may eventually
require an extension through the first half of next week as the high
remains nearly stationary.

Choppy surf along east facing shores will hold through the first
half of next week due to persistent trades locally and upstream. A
small, long period south- southwest swell will peak today generating
small surf then hold into Sunday before declining Monday. Background
southeast and south swells will then keep tiny surf along south
facing shores through much of next week. North facing shore surf
will remain nearly flat through much of next week. Models show a
gale low developing and tracking along the Aleutian Islands early
next week that may send a small northwest swell locally toward the
end of next week.

Water levels at local tide gauges are running over half a foot above
predicted and are expected to reach above the 1 foot Mean Higher
High Water threshold this afternoon due to above normal water levels
coinciding with the spring tides. This may result in nuisance
coastal flooding around the peak high tide each afternoon through
Monday. A Coastal Flood Statement has been issued to highlight this
threat.

&&

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

&&

$$

DISCUSSION...Birchard
AVIATION...Walsh
MARINE...Almanza