339
FXHW60 PHFO 081346
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
346 AM HST Wed Oct 8 2025

.SYNOPSIS...
A decaying trough of low pressure laying across the state will
maintain light east-southeast or variable breezes through
Thursday. Moisture pooled along the trough will keep moderate to
high rain chances alive in the short term with the highest
probabilities of precipitation focused along the western half of
the island chain. Trades will return Friday as this weak trough
washes out and surface high pressure northeast of the state re-
establishes a tight downstream gradient over the region.

&&

.DISCUSSION...
A wet Wednesday morning for the majority of the state under weak
southern steering flow. Many sites over the island of Oahu and
Maui County picked up around a quarter of an inch to nearly two
inches the past 12 hours from streamer showers moving up from the
south. The highest rainfall has fallen over western central Oahu
where the Waianae Mountains picked up over an inch since yesterday
afternoon. Central Oahu has received the most overnight rain with
Mililani measuring over an inch and a half of rain. Pukalani and
Lahaina on the isle of Maui as well as central Molokai and Lanai,
have also received their fair share of rain at around an inch
since Tuesday`s sunset. A welcome wetting has occurred over many
areas that have been suffering through moderate to severe drought.

While showers will become less frequent the next couple of days,
this unsettled weather pattern will hold through Friday. The main
cause to this wet pattern has been the presence of higher moisture
residing in a lower height field. Central Pacific lower mid to
upper level heights within an above normal precipitable water air
mass of around 1.4 inches (1.3 inch median for early October), in
tandem with a diffuse low level boundary shutting off trade flow,
have allowed localized breezes to interact with terrain and weak
background southerly flow to provide sufficient lift in producing
frequent showers. Much of the rain is traveling in from the ocean
within well organized bands/cells of warm low clouds and maintaining
their structure as they pass north across Hawaii. This morning`s
balloon soundings again confirm the existence of a deep near 8k
ft moistened boundary layer. This is a depth that is certainly
capable of creating thicker clouds and higher shower probabilities,
even up in higher Maui and Big Island elevations, the next couple
of days. The decaying broad low level boundary laying northeast-
to-southwest has disrupted trade flow and the benign gradient over
the state has allowed localized breezes to play more of a role.
Periods of sun warming the surface under partly cloudy conditions
will enhance late morning into early afternoon sea breezes. Lift
generated by these breezes will build clouds that will ultimately
lead to more precipitation within better wind-sheltered leeward/
southern-facing areas. As the boundary lifts north through Thursday,
the general southeast-south flow will tap into a more moisture
rich southern air mass and produce solid moderate precipitation
probabilities. Higher rain chances within lower clouds will likely
occur along the western half of the state and focus along more
southern coasts and upslope (leeward) mauka. The weakness in the
pressure field over the state will fade away by Friday. Once this
occurs, surface high pressure off the U.S. Pacific Northwest Coast
will exert more of an influence and re-establish a gradient that
will produce light to moderate trades this weekend. More overcast
and rain will regulate maximum low to mid 80 temperatures while
overnight drainage breezes will compensate for insulating clouds
as near sunrise temperatures dip into the low to mid 70s.

Mid to upper level ridging, as well as an associated drier air
mass, will begin to expand up from the southeast and envelope the
state. This will provide a bit more regional stability and
possibly peg Friday and Saturday as the driest days of the week.
Lobes of more humid air may rotate in around the southern
periphery of mid-level ridging positioned northeast of the state
early next week. The second week of October may not be as
unsettled as this week but it appears that a more wet trade
pattern sets up Sunday through mid next week as rounds of showers
move in from the east on this re-established trade flow.


&&

.AVIATION...
A weak trough orientated southwest-to-northeast across the state
has weakened regional (surface) winds and allowed pooled moisture
to initiate widely scattered showers within weak southerly low to
mid layer steering flow. Due to the lack of trades, microscale
breezes will remain the dominant near surface wind pattern across
many terminals. Higher resolution models are focusing the highest
morning rain in and around Oahu and Kauai. The boundary is
forecast to lift north through the day and this will align
statewide winds to a south or southeast direction. Tempo MVFR
decks and visibilities within more moderate showers while short
lived, isolated IFR conditions are possible within pockets of
heavier rain.

AIRMET Sierra for mountain obscuration is in place over Maui,
Molokai, Lanai, Oahu, and Kauai early this morning due to
occasional low cloud decks decreasing visibilities within
showers. Conditions should improve around sunrise.


&&

.MARINE...
A trough draped over the coastal waters will continue to slowly
drift northwest during the next several days and bring light
south or southeast flow across all zones. This flow should also
give way to land and sea breezes that will be observed over the
nearshore waters. Gentle to moderate easterly trades will return
by this weekend and continue into early next week as high pressure
builds far northeast of the state.

The current small, medium period, north northwest swell will be
down from previous days and continue to fade through the weeks
end. Thus, surf along north-facing shores will remain near or
below the October average through most of the week. Forerunners
from the next, more significant moderate, long period northwest
swell are progged to arrive by mid day Sunday, with the event
lasting through early to mid next week. During its peak, surf
along north-facing shores may approach High Surf Advisory
criteria.

Background south southwest swell energy will bring tiny to small
surf along south-facing shores today. A small, long period south
southwest (190-200 degree) swell will fill in Thursday morning and
bring a slight increase to surf along south-facing shores through
late Friday.

Below average surf along east-facing shores is expected for the
remainder of this week as weak flow prevails. There will be a
little boost by this weekend as trades return. In addition, a
small, medium to long period, easterly swell from Tropical Cyclone
Priscilla in the East Pacific is forecast to arrive late Saturday
into Sunday.

Peak high tides associated with the lunar cycle will lead to
minor coastal flooding along shorelines and low lying coastal
areas through this weekend. Coastal flooding will coincide with
the daily peak tide each morning. A Coastal Flood Statement
remains in effect for all coastal areas through Friday, but will
likely need to be extended.

&&

.FIRE WEATHER...
Weak localized and/or variable breezes and a higher frequency of
showers will help maintain below critical fire weather thresholds
the next several days. Inversion heights across the state will
range from as low as 5,000 to as high as 9,000 feet.

&&

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

&&

$$


DISCUSSION...Blood
AVIATION...Blood
MARINE...Thomas
FIRE WEATHER...Blood