Paauilo, Hawaii Weather Forecast Discussion

267
FXHW60 PHFO 221331
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
331 AM HST Mon Sep 22 2025
.SYNOPSIS...
Moderate to locally breezy trade winds will ease Tuesday and
Wednesday as the ridge north of the state weakens and a surface
trough develops far northeast of the islands. Showers will be
focused over windward slopes, and while most leeward areas will
experience minimal shower activity, the Kona slopes of the Big
Island will see scattered afternoon showers, some briefly heavy.
The trough will drift north of the islands on Thursday,
disrupting trade winds and leading to a land and sea breeze
pattern into the weekend.
&&
.DISCUSSION...
A slightly unstable, moderate to locally breezy trade wind flow
remains in place. Trades are being driven by a surface ridge
roughly 750 miles north of Kauai, and a broad upper-level trough
centered a couple hundred miles north of the islands is keeping
the inversion slightly weak and elevated. As a result, pockets of
moisture moving along the trade wind flow are producing rainfall
slightly heavier than normal. That said, rainfall continues to
favor windward slopes, generally less than a half an inch in the
wetter areas overnight, while a few showers briefly pass over
leeward areas. The exception is leeward Big Island, where
scattered showers that developed yesterday afternoon lingered
into the night and dropped in excess of two inches of rainfall
just north of Kailua-Kona in the evening. Expect little change
today with scattered showers windward and active rainfall on the
Kona slopes of the Big Island this afternoon.
Trade winds will gradually ease Tuesday and Wednesday. Tuesday`s
decline will be produced by the weakening of the surface ridge by
a North Pacific front. The trades will further weaken on
Wednesday as surface low pressure forms about 750 miles northeast
of the islands along the stalled front. This will relax the local
pressure gradient, even as stronger high pressure develops
farther to the north. Expect showers to continue to favor
windward slopes and the Kona Districts of the Big Island, and as
the upper-level trough supporting the surface low digs over the
islands on Wednesday, an isolated heavy shower cannot be ruled
out.
The latest runs of the GFS and ECMWF are strongly suggesting that
trade winds will become disrupted Thursday into the weekend as
the surface low stalls about 500 miles north of the state. A land
and sea breeze regime should dominate over the islands, leading to
showers favoring interior areas each afternoon. A sharp mid- to
upper-level trough supporting the surface low does not appear to
be robust, but its positioning over the island chain may produce
enough instability to trigger a few heavy showers. While there is
no clear signal of organized moisture over the region, the GFS and
ECMWF are hinting at some deeper moisture that could lead to more
shower activity over the western end of the island chain.
&&
.AVIATION...
Moderate to locally breezy trades will taper off Tuesday and
Wednesday. Low cigs and SHRA will favor windward and mauka
locations. While MVFR conds are possible in SHRA, VFR should
prevail.
No AIRMETs currently in effect.
&&
.MARINE...
Moderate to locally fresh trades prevail through Wednesday, then
a developing low pressure system northeast of the islands weakens
large scale wind speeds, and winds will become light and variable
from Thursday through Sunday.
The current south swell will slowly decline today. The next small
south swell arrives on Tuesday, peaking overnight, and then
slowly declining on Wednesday. A third, small long period south
swell will fill in starting on Thursday and last into next
weekend. Surf heights from these swells will remain near seasonal
averages along south facing shores through much of this week.
A trough northeast of Hawaii will generate a short period fresh
north swell that will reach the islands by Wednesday night, then
peaking from late Thursday into Friday, this swell may bring small
to moderate surf along exposed shorelines. Evolution of this
trough and its close proximity to the islands brings increased
uncertainty to the surf height forecast this week along north and
east facing shores.
&&
.FIRE WEATHER...
Locally breezy trade winds and minimal rainfall over most leeward
areas will produce conditions just below critical thresholds
today, followed by gradually easing trade winds Tuesday and
Wednesday. Lighter winds with afternoon sea breezes are expected
Thursday into the weekend. The inversion will hold around 6,000 to
8,000 feet today.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Wroe
AVIATION...Walsh
MARINE...Bohlin
FIRE WEATHER...Wroe

NWS HFO Office Area Forecast Discussion