305
FXHW60 PHFO 160156
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
356 PM HST Sat Nov 15 2025

.SYNOPSIS...
High pressure to the northeast will move to the east over the
coming days, and moderate trades will weaken. Increased shower
activity is expected Monday through Wednesday as a front
approaches from the northwest, and an upper level trough develops
near the islands.

&&

.DISCUSSION...
There have been some changes to the forecast with the afternoon
package to refine various aspects. Through tomorrow night, the
PoPs were adjusted towards the latest run of the National Blend of
Models (NBM), with the exception of the Big Island were a blend of
the GFS and ECMWF was used as the NBM seemed to be a little wet.
For Monday and Tuesday, the NBM was heavily used for PoPs, with
some nudging near the Big Island towards the GFS solution.
Thunderstorm areas were reduced, following the previous trend of
using the coldest 500 mb temperatures, however confidence is low
for any thunderstorm development. Snow chances for the Big Island summits
remains for Monday afternoon through much of Tuesday night, with
summit temperatures reduced to be better aligned with that
possibility. Monday night through Wednesday afternoon, the Big
Island winds were adjusted upwards utilizing the GFS winds. More
details on these changes below.

High pressure to the northeast will maintain a trade wind flow
through the remainder of the weekend. A front far to the northwest
will continue to move to the east, pushing the high to the east.
This will in general weaken the trade winds for the start of the
week, with the winds turning a bit south of east. The ECMWF keeps
the front to the northwest of the islands, while the GFS would
usher it closer to the islands Tuesday. Both models develop an
upper level low over the western islands Monday, which merges with
the upper level trough associated with the approaching front to
the northwest Tuesday night. On the east side of the upper level
low, winds will draw moisture towards the islands, with most of
that moisture focused over the Big Island. The colder temperatures
aloft will then bring the possibility for some wintry weather for
the Big Island summits. This isn`t an organized frontal system
moving over the Big Island, so not expecting a significant winter
event, but certainly can`t rule out some snow showers.

The upper level low will bring colder temperatures to the islands,
with the ECMWF and GFS both showing pockets of -10C, or slightly
colder, Monday afternoon through Tuesday night. While this is on
the colder side of normal for this time of year, its generally
within 1 standard deviation. Additionally, the precipitable water
values remain near normal in the areas with the coldest 500 mb
temperatures. This would suggest not all parameters are lining up
for the development of thunderstorms. While winds are weakening
Monday, believe there will be enough of a trade wind component to
inhibit thunderstorm development, but that could change as we head
into Tuesday with winds weakening a bit more. That being said, at
that time the question will remain as to whether or not the cold
temperatures and precipitable water will line up.

That all being said, there remains a possibility, so have left
slight chance of thunderstorms in the forecast. Anticipate that as
the forecast period starts to be covered by the high resolution
guidance (Sunday afternoon`s run), we should get a better idea for
how things will pan out. At this time, suspect the rain focus
will be on the Big Island.

The second half of the week will have whatever remains of the
front moving to the the east, and a new upper level low that
develops along the frontal upper level trough moving to the west.
A new high building in behind the front will bring returning
trades to the region, which will carry some of the residual
showers from the front into the islands.


&&

.AVIATION...

Moderate trades are on the decline for the next few days. Low cigs
and SHRA should be focused mainly over windward and mauka
locations. MVFR conds possible in any SHRA, otherwise VFR
prevails.

No AIRMETs in effect.


&&

.MARINE...
Moderate to locally strong E trades persist today then gradually
weaken as high pressure to the NE drifts SE and weakens. An upper
level trough forms SE of the coastal waters Monday causing
moderate trades to then veer to ESE and slowly weaken through
Tuesday. Additionally, a front will advance into the offshore
waters by Tuesday afternoon bringing locally strong ENE winds
behind it before weakening over the coastal waters midweek. There
is the slight chance for thunderstorms Monday through Wednesday.

Surf along N facing shores remains small early this afternoon, but
a small to moderate, medium to long period NW swell will fill in
this evening into tonight in maintenance of elevated surf through
the weekend. Small long period forerunners are evident on the
NDBC buoys 51101 and 51001 early this afternoon. A moderate long
period NW swell is then expected to arrive late Tuesday and peak
Wednesday near High Surf Advisory thresholds before declining by
the end of next week.

Surf along E facing shores will decline through the weekend due
to the weakening of the local and upstream trade winds. Large
choppy short period surf for N and exposed E shores is possible
by the middle of next week depending on the evolution of the
approaching cold front. For S shores, tiny background southerly
swell remains through the forecast period.


&&

.FIRE WEATHER...
Weakening winds, combined with higher relative humidity due to the
increased moisture near the islands will maintain the low fire
weather threat over the next several days. Inversion heights
around 6K feet will continue tonight but could raise to 7-9K feet
Sunday/Monday.


&&

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

&&

$$


DISCUSSION...M Ballard
AVIATION...Walsh
MARINE...JVC
FIRE WEATHER...M Ballard