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FXHW60 PHFO 010101
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
301 PM HST Sun Aug 31 2025

.SYNOPSIS...
Beneath a persistent blanket of high clouds, moderate trades
deliver limited low clouds and showers to windward and mauka areas
for the remainder of the week.

&&

.DISCUSSION...

Afternoon water vapor imagery clearly shows a closed upper low
parked NW Kauai drawing north a plume of moisture from the deep
tropics. In response, deep layer SW flow extends down to around
700mb and PWATs have spiked to about 1.7" per this afternoon`s
sounding out of Lihue. Saturation with respect to ice in the 20-
25kft layer is indicative of the partially transparent band of
high clouds that will be a fixture over the islands through most
of the coming week. A weakened trade wind inversion around 8kft is
observed which matches well with radar-indicated shower tops
penetrating to 10kft or so. Interior showers developed over the
islands this afternoon in response to daytime heating with the
resident envelope of low-level moisture, but they have largely
been disorganized. This is likely a consequence of high clouds
short-circuting the sea breeze which only briefly manifested over
Oahu where winds have already backed to the ENE at HNL. The lack
of organized surface convergence has therefore translated into a
lack of shower organization. Interior areas will clear this
evening giving way to clear skies in the lower levels and high
clouds aloft with light to moderate trades delivering pockets of
showers windward and mauka through the night.

The latest modeling suggests today will represent the minimum in
winds for the week, though not by much, as the trade wind belt
rebounds slightly northward and the upper low NW of Kauai gradually
lifts north away from the islands. Moderate, stable trades are
forecast to prevail through the end of the forecast period. Rainfall
remains limited as drier air returns early this week and dewpoints
fall to typical values in the upper 60s.

&&

.AVIATION...

Light to moderate trade winds will allow local sea breezes to
continue in sheltered leeward locations through this evening,
with clouds and showers over some leeward and interior areas.
Tropical moisture moving across the islands combined with some
weak instability aloft may bring some enhanced showers through
tonight, with periods of MVFR possible. Otherwise, VFR should
prevail.

No AIRMETs are currently in effect, but AIRMET Sierra may be
needed over portions of the islands if showers become more
widespread.

&&

.MARINE...

A ridge of high pressure north of the state will remain displaced
to the south in response to large low far to the north. This will
maintain moderate trades through most of the forecast period, with
some localized sea breezes, especially across leeward waters.

Surf along south facing shores will continue to decline through
Monday as the swell fades, returning to background levels for most
of the coming week. Surf along north facing shores will see a
boost on Monday due to a small, short- to medium-period swell.
This swell will quickly be overshadowed by longer period energy
out of the northwest starting Monday night and peaking on Tuesday.
Surf will increase again from the influence of this swell, but
remain below advisory levels. A reinforcing pulse out of the north
should arrive around the same time the northwest swell arrives. A
mix of north and northwest swells are expected to continue through
Thursday. Below average surf is expected to continue along east
facing shores persisting through early next week.

Peak monthly high tides, combined with water levels running higher
than predicted, may lead to minor flooding along the shoreline and
in low-lying coastal areas toward the end of next week. Coastal
flooding may be possible around the daily afternoon peak tide.

&&

.FIRE WEATHER...

Moderate trades prevail for the remainder of week delivering
limited showers windward and mauka. Modest drying commences during
Monday as the resident area of low-level moisture exits to the
west and dewpoints return to typical values in the upper 60s.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$


DISCUSSION...JVC
AVIATION...Ahue
MARINE...TS
FIRE WEATHER...JVC