331 
FXHW60 PHFO 061859
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
859 AM HST Mon Oct 6 2025

.UPDATE...
Have updated the forecast this morning to increase the chance of
showers for the remainder of today over most of Oahu, and also the
mountains of Kauai. The trough moving in has been efficient in
producing showers, and wanted to better reflect the timing in the
forecast.

&&

.SYNOPSIS...
A band of embedded showers are being escorted by a trough just
north of the Hawaiian Islands this morning, bringing periods of
showers mainly to Kauai and Oahu today. Winds will weaken and 
become more southeasterly, leading to the development of a land 
and sea breeze regime, persisting through Thursday. Thereafter, 
moderate trades return at the end of the week.

&&

.PREV DISCUSSION.../ISSUED 330 AM HST Mon Oct 6 2025/

Latest satellite imagery continues to show an unambiguous band of
embedded showers escorted by a north to south propagating trough 
just north of the Hawaiian Islands. Model guidance of the GFS and 
ECMWF has done a fairly decent job identifying this trough, 
portraying isolated shower activity descending upon Kauai early 
this morning and is progged to extend further southward into Oahu 
shortly thereafter before dissipating. An uptick in shower 
activity has been presented over Kauai and dialed down over Oahu 
as this feature passes southward, but given the quick nature of 
the trough and its weakening status, anticipated rainfall 
accumulations are expected to be minimal. That said, a clear-cut 
mid-level low near 29N 150W as of 0300 HST (13z), where towering 
cumulus and heavier showers are being observed well northeast of 
the islands are expected to keep distance away from the islands, 
and not impactful to Hawaiian weather today.

A secondary trough, slightly weaker in composition, extends
southeastward from the aforementioned mid-level low and is slowly
meandering westward. Winds across the Hawaiian Islands have 
noticeably eased in response of each passing trough, progged to
veer east-southeasterly, resulting in a more pronounced land and
sea breeze regime lasting through early Thursday. In such a
pattern where the local scale winds are virtually absent, island
heating will support sea breezes during the day, which will 
enhance leeward and interior shower activity, and overnight 
cooling will drive land breezes at night, clearing the night skies
and limiting showers. 

Light to moderate trades begin to reestablish late Thursday with
the introduction of a strong high pressure ridge axis building in
far to the northeast of the region. Latest model guidance suggests
this pressure ridge will slowly migrate southward toward the
middle of next weekend, indicative of moderate trades across much
of the state during this time. There is a bit of uncertainty in
the forecast for the latter half of the week, however, as some
deterministic model guidance is hinting at another surface trough
developing just north of the Hawaiian Islands late this week,
which would disrupt winds and increase shower activity. Confidence
remains low concerning the exact timing and placement, or whether
the feature will develop.

AVIATION...

Light to moderate northerly winds are pushing a band of low level
clouds with embedded showers over Kauai early this morning. This 
band is expected to push over Oahu during morning commute hours 
and dissipate over the island through the afternoon. AIRMET 
Sierra is currently in effect for mtn obsc over N to SE sections 
of Kauai as this band of showers drifts south generating periods 
of MVFR conditions. AIRMET Sierra may need to be expanded for Oahu
as this band continues to drift south and settle over the island 
later this morning and afternoon. 

Winds are expected to weaken a notch this afternoon and veer more
southerly as the trough weakens and retrogrades west and other
trough deepens east of the state. Expect afternoon seabreeze 
conditions will develop each afternoon generating periods of MVFR 
conditions over sheltered leeward and interior locations. Land 
breeze will develop overnight with conditions improving to mostly
VFR conditions. This pattern is expected to repeat over the next
couple of days. 

MARINE...

A trough over the northwest coastal waters is moving southeast 
and will move over Kauai this morning. As the trough moves over 
Kauai, scattered showers are expected along the trough with moderate
northeast trade winds filling in over Kauai waters, while 
elsewhere gentle to locally moderate easterly trade winds are 
expected through tonight. Another trough northeast of the offshore
waters will slowly drift west over the next few days. Tuesday 
through Thursday light to gentle southeast flow across all zones
are expected and will also give way to localized land and sea 
breezes. Moderate trades will fill in from east to west at the end
of the weak as high pressure builds far northeast and drifts 
southeast. 

The current moderate north-northwest swell that peaked well above 
High Surf Advisory (HSA) levels Sunday has begun to decline quickly
overnight and will continue to decline today. Also, a small medium
to long period northwest (320 deg) swell is expected to fill in 
this afternoon, peak tonight and slowly decline Tuesday. No significant
north swells are expected through the week except the potential 
for a moderate medium to long period northwest (320 deg) swell 
Sunday into early next week. 

A small, long-period southwest swell has started to fill in 
overnight with long period 16 second forerunners. The swell is 
expected to peak today before subsiding Tuesday. Another small 
long- period southwest (200 deg) swell is possible by the later 
half of the week. Surf along east- facing shores will remain below
average through the week except for select shorelines exposed to 
the current north swell today.

Peak high tides associated with the lunar cycle will lead to minor
coastal flooding along shorelines and low lying coastal areas
starting Tuesday through the weekend. Coastal flooding will
coincide with the daily peak tide each afternoon.

&&

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

&&

$$

UPDATE...Parker/Wroe
DISCUSSION...Pierce 
AVIATION...Almanza 
MARINE...Shigesato 
FIRE WEATHER...Pierce