825
FXHW60 PHFO 170106
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
306 PM HST Sun Nov 16 2025

.SYNOPSIS...
Moderate easterly trade winds will focus showers across windward
slopes through Monday, while a developing upper level low just
southwest of the islands gradually pulls a swath of high clouds
overhead. The upper level low will strengthen mid to late Tuesday
into Wednesday and bring an increased threat of heavy showers and
isolated thunderstorms on increasing trade winds, with flood
potential increasing over the eastern end of the island chain.
Chances of heavy rainfall will diminish late Wednesday and
Thursday, though breezy and somewhat wet trade wind weather is
expected. Another round of unsettled weather is possible next
weekend.

&&

.DISCUSSION...
Moderate easterly trade winds will continue to focus showers
across windward slopes through Monday. A sharp upper level trough
bisecting the state this afternoon will develop into an upper
level low centered just southwest of the island chain tonight. The
upper low will pull a shield of high clouds over the area from
the south and also erode the mid level ridge overhead, leading to
the elimination of the inversion and a slight destabilization of
the atmosphere. This could produce some enhancement of the showers
in the trade wind flow, mainly within a diffuse band of moisture
moving across the western half of the island chain tonight.

Trade winds will briefly diminish Monday night and early Tuesday
as the atmosphere further destabilizes. Trades will ease as a cold
front advances to within 200 miles northwest of Kauai and pushes
the weakened subtropical ridge generating the trades to far
northeast of Hawaii. The upper level trough driving the front will
begin to absorb the upper level low just southwest of the state.
The resulting negatively titled upper level trough will produce
difluence aloft within a narrow jet stream over the islands. The
greatest forcing associated with this jet stream will likely be
just south of the Big Island, where an area of deep tropical
moisture will be drawn northward. At this time, GFS and ECMWF
ensemble guidance suggest that the deepest moisture and greatest
threat of heavy rainfall will remain south of the islands through
at least midday, with chances for rainfall along southeast and
windward Big Island increasing during the afternoon. Meanwhile,
closer to the colder temperatures aloft along the upper level
trough axis, an isolated thunderstorm or heavy shower cannot be
ruled out across other islands. In addition, a shield of thick
high clouds will cover the entire island chain.

The highest chances for heavy rainfall favors late Tuesday
afternoon or early evening into Wednesday, though differences in
model guidance are producing some uncertainty. The wetter GFS is
maintaining a more persistent upper level trough with somewhat
strong difluence aloft, while the latest run of the ECMWF depicts
a weaker upper level trough being absorbed more quickly into the
large upper trough to the west. Both models suggest that the front
will dissipate just north of the islands and that trade winds
will ramp up as strong surface high pressure passes far to the
north. Under this breezy, moist, and unstable trade wind flow,
windward areas will be the focus for heavy rainfall, while leeward
communities experience briefly heavy and potentially frequent
passing showers. The greatest threat for flooding continues to
point toward the eastern end of the island chain, mainly on Big
Island, where difluence aloft may produce precipitable water
values in excess of 2 inches. With trade winds blowing and thick
high clouds limiting convection, the greatest flood potential
appears to be over windward and southeast Big Island, where the
12Z GFS Ensemble 90th percentile solution shows 24 hour rainfall
totals of around 5 inches. Given the model differences regarding
potential rainfall totals, confidence is not high enough to issue
a Flood Watch at this time. Along with the flood threat, the high
summits of the Big Island could experience periods of heavy snow
and strong winds, but the big question will be the snow level,
which will be hovering close to summit elevation. We will hold
off on any winter weather headlines for now due to uncertainty.

The threat for heavy rainfall will decrease during the day on
Wednesday as high clouds diminish, but breezy and wet conditions
are expected into Thursday. The heavy rainfall threat will drop as
the upper level trough near Hawaii gets absorbed by the deeper
upper level trough to the west, greatly diminishing difluence
aloft. The strong surface high passing to the north will maintain
breezy trade winds, and even though precipitable water will be
decreasing, the GFS and ECMWF keep abundant moisture around the
islands, suggesting a rather wet pattern.

A brief period of stable and drier trade wind conditions is
expected on Friday, followed by another round of potentially
active weather next weekend.

&&

.AVIATION...
Gentle to breezy easterly trade winds will hold through tonight
and veer slightly east southeast Monday while weakening over the
western half of the state. VFR conditions prevail across the state
with a few spots briefly reaching MVFR conditions due to passing
CLD and SHRA as an area of moisture continues to move through Oahu
and Kauai this afternoon into evening hours. High CLD will build
in from south around Big Island and Maui tonight into Monday. MVFR
conditions are then possible across all windward and mauka areas
overnight and during the early morning hours along windward and
mauka areas as another band of moisture trapped with the trade
flow moves east to west. Weaker winds Monday suggest that local
land/sea breezes will become more dominant with possible CLD and
SHRA building along the more sheltered leeward coasts and interior
during the afternoon hours before clearing overnight with the
land breeze, especially for Kauai and Oahu. Overcast conditions
will be possible for the eastern half of the state Monday as high
clouds continue to build overhead.

No AIRMETs are currently in effect but could be necessary
overnight and early morning Monday as the next band of moisture
moves through.

&&

.MARINE...
Trade wind speeds will continue to decrease and veer from a more
E to SE direction from Monday to Tuesday as the high pressure
ridge north of the Hawaiian Islands drifts E in response to an
approaching cold front far NW of the state and a surface trough
forming over the islands. Additionally, the cold front will
advance into the offshore waters by Tuesday evening, bringing
near-gale-force winds in its wake before the front diminishes over
the NW coastal waters on Wednesday. Expect Small Craft Advisories
to be issued for most of the Hawaiian coastal waters from at
least Wednesday into Friday due to a combination of strengthening
winds and rising seas. Isolated thunderstorms are possible over
the Hawaiian waters through much of this week.

Expect multiple overlapping NW swells this week. This will keep
surf heights boosted along exposed N and W facing shores. The
challenge with this pattern will be in tracking the multiple swell
energies from similar directions and similar periods. Wave height
model guidance has trended towards combining these different
swells for the Monday through Friday time period. Continued to
decrease the NW swell heights from model output by a few feet
with this forecast package to account for this discrepancy.

A small medium period NW (310-320 degree) swell peaked this
afternoon and is expected to slowly decline into Monday. The next
moderate, medium to long period NNW (320-340 degree) swell will
then arrive late Tuesday, peaking Wednesday near High Surf
Advisory thresholds along exposed N and W facing shores before
gradually declining through the end of the week. Another
overlapping small, medium period NNE (010-020 degree) swell
arrives from Thursday into Friday. Then another small, long period
NW (320-330 degree) swell arrives in Hawaiian waters by Friday,
then holds through the weekend.

Surf along E facing shores will decline into Monday due to the
weakening of the local and upstream trade winds, though there may
be a brief uptick late tonight into Monday morning as a small
medium period NE (040 degree) swell arrives. As the high pressure
ridge moves east later this week, the combination of a long
easterly fetch of 15 to 20 kt winds upstream of the islands from
Tuesday through Thursday, along with strengthening local winds
along the cold front, will produce moderate and choppy surf along
E shores. For S shores, periods of tiny background south swell
energy will linger.

&&

.FIRE WEATHER...
Moderate trade winds and seasonably higher humidity will maintain
conditions well short of critical fire weather thresholds through
Monday as the inversion gradually weakens. Wet conditions are
expected Tuesday into Thursday, with heavy rainfall possible over
recent burn areas on the Big Island.

&&

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

&&

$$

DISCUSSION...Wroe
AVIATION...Almanza
MARINE...Farris
FIRE WEATHER...Wroe