646 
FXHW60 PHFO 251338
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
338 AM HST Thu Sep 25 2025

.SYNOPSIS...
A low pressure system north of the Hawaiian islands moves slowly
southward, bringing an increase in shower activity especially to
the Niihau, Kauai, and portions of Oahu through Friday. The 
heaviest showers will be fixated on Kauai, where isolated 
thunderstorms will also be possible. Additional showers and
thunderstorms may trigger on the Big Island Friday and Saturday
afternoons. Trades return to the forecast under a more stable 
weather pattern by the end of the weekend.



&&

.DISCUSSION...
Latest satellite imagery continues to depict a low pressure system
and associated cold frontal passage northeast of the Hawaiian 
Islands, meandering southwestward slowly. As the low tracks toward
the state, it will begin to bring colder air aloft, destabilizing
the atmosphere today and tomorrow, increasing cloud coverage and 
shower activity. Heaviest showers will be isolated to the northern
portion of the state, namely across Niihau, Kauai and portions of
Oahu throughout the day today and into early Friday.

The aforementioned front is progged to weaken to a trough later
today. Winds veer southerly during this time, but remain light in
speed, allowing localized sea breezes to develop during the 
afternoon hours, resulting in cloud coverage and shower activity 
across interiors of all islands. Latest model guidance suggests 
Kauai will be engulfed in widespread showers throughout the latter
half of today, with northern aspects of Oahu seeing showers from 
the southern edge of the shower band, though lingering showers may
make way across Oahu at times. 

Latest model guidance suggests overall shower activity becomes
dispersed by late Friday, however, maintained lighter winds will 
continue to allow localized sea breezes during the afternoons,
still capable of producing showers on interiors of all islands. 
Meanwhile, deeper unstable tropical moisture will get pulled into 
the sea breeze pattern, triggering a brief period of enhanced 
shower activity and thunderstorms across the Big Island Friday and
Saturday. 

Toward the latter end of the weekend, the low pressure system will
begin to propagate westward and allow ridging to rebuild back over
the islands. As a result, winds will back into a more easterly 
direction, reintroducing stable trades and associated showers to 
the forecast. Expect moderate to locally breezy trades along with
brief passing showers through much of early next week, favoring 
windward and mauka areas in the overnight to early morning hours.


&&

.AVIATION...

Light and variable winds persist as a weak frontal passage 
continues to approach the islands from the north. Expect periods
of MVFR conditions due to shower activity and cloud coverage
predominately for PHLI, PHNL, and PHJR throughout the day. Isolated
thunderstorms possible. Otherwise, VFR conditions prevail 
elsewhere.

No AIRMETs are currently in effect.


&&

.MARINE...
A low pressure system about 600 nm northeast of the coastal waters
has an associated cold front that is moving into the coastal
waters near Kauai early this morning. The front and low are
expected to move south, with the front weakening to a trough,
which is expected to stall near Kauai or Oahu this afternoon. 
This system has disrupted the trade wind flow, and brought lighter
winds to the region. Trade winds are expected to build back in by
Sunday in response to a high pressure ridge moving in north of the
islands.

The ECMWF and GFS are in good agreement with an upper level low,
associated with the above mentioned surface feature, moving south
today, and being north of Kauai tonight and tomorrow. This will
provide some instability that could lead to a few thunderstorms
over the coastal and offshore waters. 

This low pressure system is sending a moderate medium period 
N-NNE swell to N facing shores that will peak this afternoon. 
There is also a small NW swell that will be filling in through 
the weekend, helping to keep surf heights slightly elevated. A 
small medium period NW swell is then expected to fill in Monday 
and decline slowly through next week. Tiny to small background N 
and NW pules will keep north shores from going completely flat for
the remainder of next week.

Surf for south facing shores will remain small today, before a 
small long period south swell arrives on Friday and peaks over the
weekend at, or slightly above, the September average (5 ft).

Surf for east facing shores will likely see an increase from the 
N-NNE swell today and Friday. The islands to see the greatest 
increase would be Kauai and Oahu, as these islands are most 
directly within the fetch area of the low to the north. This swell
will fade out by the weekend. Trade wind chop could increase by 
Sunday as trade winds return.


&&

.FIRE WEATHER...
Light and variable winds with increasing humidity values across 
the state through the weekend will help maintain below critical 
fire weather thresholds over the next several days. Moderate 
trades and drier conditions expected by next week. Temperature 
inversion heights near Maui and the Big Island today will range 
from 7,000 to 8,000 feet elevation.


&&

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

&&

$$


DISCUSSION...Pierce
AVIATION...Pierce
MARINE...M Ballard
FIRE WEATHER...Pierce