Waianae, Hawaii Weather Forecast Discussion

111
FXHW60 PHFO 280137
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
337 PM HST Sat Sep 27 2025
.SYNOPSIS...
Trade winds will build tonight and will be locally breezy Sunday
and Monday. The increasingly stable trades will focus showers
across windward areas, with afternoon showers developing along
leeward slopes of the Big Island. Winds may ease by Friday.
&&
.DISCUSSION...
Trade winds are spreading westward across the island chain as
slight instability lingers. The compact surface low that cut off
the trades during past couple of days weakened to a trough
northwest of Kauai today, allowing deep high pressure far north of
the islands to push resurgent trade winds in from the east. The
upper-level low associated with the trough is meandering to the
north of Kauai. This feature is triggering thunderstorms directly
underneath, along the outer fringes of the coastal waters to the
south and southwest of Kauai and Oahu in a pool of lingering
moisture, and over the heated high terrain of the Big Island. As
trade winds continue to build westward overnight, expect
thunderstorms to dissipate over interior Big Island while spotty
heavy showers linger through the evening over leeward slopes.
Elsewhere, modest shower activity will be focused along windward
slopes, and thunderstorms should persist near or just outside of
the Kauai coastal waters.
Locally breezy trade winds will become established on Sunday as
the trough moves away from the islands and surface high pressure
settles far to the north. Upper-level ridging building in from the
east will bring increasingly stable conditions that will suppress
thunderstorms over interior Big Island and allow for only
scattered afternoon showers over the Kona slopes. The building
ridge aloft will push the upper-level low westward, keeping
thunderstorms outside of the Kauai coastal waters. Otherwise,
expect typical trade wind weather with limited showers windward
and mostly dry conditions leeward.
Moderate to locally breezy trade winds and stable conditions will
prevail through much of the work week. A band of moisture is
expected to provide a boost in shower activity Tuesday night and
Wednesday. The surface high to the north will begin to weaken
during this time, likely leading to a very gradual easing of the
trade winds. Recent guidance has been a bit inconsistent, but the
overall trend favors trades dropping into light to moderate
strength by Friday.
&&
.AVIATION...
A low pressure north of Kauai is causing some SHRA around Kauai
and Oahu and a few isol TSTMs across waters southwest of the
coastal waters. MVFR conds can be expected in any SHRA but VFR
should prevail elsewhere. Trades continue to fill in through
tomorrow, focusing SHRA and MVFR conds back to typical windward
and mauka areas.
No AIRMETs are in effect.
&&
.MARINE...
A surface trough just west of the offshore waters will continue
to drift west and weaken through Sunday. Lingering instability
will keep isolated thunderstorms over the western offshore waters
through early next week. Moderate to locally fresh easterly trade
winds will continue to build in from the east tonight into Sunday
and gradually strengthen to locally strong by Sunday afternoon,
with a Small Craft Advisory (SCA) for the windier waters and
channels around Maui County and the Big Island possible Sunday
afternoon/evening through early next week.
Surf along south facing shores will hold through the weekend as a
small to moderate medium- to long-period south swell continues. A
series of small medium-period south swells will keep surf from
going flat through the middle of next week.
Fading energy from the north-northeast swell will continue to fall
through tonight. A small medium- to long-period northwest swell
will continue to fill in this evening before falling on Sunday. A
series of tiny to small swells from the north and northwest will
trickle in through the middle of next week.
Surf along east facing shores should start to increase on Sunday
as trade winds return, along side a tiny medium-period easterly
swell generated from Hurricane Narda far to the east.
&&
.FIRE WEATHER...
Conditions will remain below the critical fire weather threshold,
even as locally breezy trade winds bring drier conditions Sunday
through Tuesday. A brief period of wetter trade wind weather is
expected on Wednesday, followed by decreasing winds later in the
week.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Wroe
AVIATION...Walsh
MARINE...Ahue
FIRE WEATHER...Wroe

NWS HFO Office Area Forecast Discussion