977
FXHW60 PHFO 190219
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
419 PM HST Tue Nov 18 2025

.SYNOPSIS...
Deep tropical moisture will continue to stream over the eastern
end of the state through Wednesday. This moisture will interact
with a surface trough to bring periods of heavy showers through
Wednesday, especially for windward portions of Maui and the Big
Island. The chance of heavy rainfall diminishes late Wednesday
into Thursday, but breezy and showery trades will persist. A brief
period of stable and drier trade wind conditions is expected on
Friday, followed by more showery weather into the weekend as a
cold front advances toward the island chain.

&&

.DISCUSSION...
Visible satellite imagery continues to show thick mid to upper
level clouds streaming in from the southwest over the Big Island
this afternoon, with PWATs near 2.0 inches. Meanwhile, the latest
surface analysis depicts a surface trough southeast of the Big
Island moving towards the west. Guidance also continues to show
an upper level trough northwest of the island deepening tonight as
it moves east which will keep unstable conditions across the area.
Expect these troughs to continue to interact with the deep
tropical moisture moving across the Big Island to bring periods
of heavy showers to the area. The latest guidance continues to
show the potential for heavy rain across the Big Island will
continue through Wednesday, but total accumulations are now on the
lower side as guidance has started to back off. Nonetheless, some
locally heavy rain remains possible and could produce nuisance
flooding in the typical areas with 1 to 2 inches of rain expected
across windward areas of the Big Island. Any potential threat for
heavy rain will decrease late Wednesday.

The thick clouds over the Big Island summits produced some light
snow accumulations last night, with precipitation quickly
transitioning to rain this afternoon. Expect precipitation to
become a mix of rain and snow overnight as snow levels fall to
around 12,000 feet. Guidance doesn`t show much change in summit
conditions on Wednesday with an additional 1 to 2 inches of snow
possible so decided to extend the current Winter Weather Advisory
through Wednesday evening.

As for the rest of the state, water vapor imagery shows a small
dry air slot filling in which explains the lack of clouds over
the smaller islands. Radar imagery this afternoon show mainly
scattered windward and mauka showers moving across the smaller
islands. Moderate trades will continue across these areas as high
pressure builds far north of the region.

Breezy and wet conditions are expected into Thursday. The strong
surface high passing to the north will maintain breezy trade
winds, and even though PWATs will be decreasing, both the GFS and
ECMWF keep abundant moisture around the islands, pointing to a
rather wet pattern.

A brief period of stable and drier trade wind conditions is
expected on Friday, followed by the potential for more showery
weather into the weekend and early next week as a cold front
approaches the island chain. Once again models vary on timing and
location so please pay attention for further updates.

&&

.AVIATION...
Trade winds expected to strengthen by Wednesday. Layered clouds
over the Big Island will bring light icing from 140-FL260 into
Wednesday. AIRMET Tango posted for tempo moderate turbulence
between FL250 and FL400 all islands. AIRMET Tango will likely be
dropped tonight as guidance suggest a decrease in turbulence.

Showers expected to increase tonight into Wednesday as trades
build. AIRMET Sierra likely to be issued for tempo mountain
obscurations later tonight for some windward areas, particularly
the eastern half of the state.

&&

.MARINE...
Moderate trade winds will steadily increase over the next 24
hours. Local trade winds are near a minimum this afternoon as a
front, currently just beyond the offshore waters 240 nm northwest
of Kauai, has eroded and pushed the subtropical ridge to the east.
The weakening front is not expected to push much farther east,
and northeast winds are already beginning to increase at NOAA buoy
51001 as robust surface high pressure behind the front is
starting to exert influence. As the front dissipates and the
surface high moves north of the state tonight and Wednesday,
expect trade winds to ramp up, eventually reaching near gale
strength in the Alenuihaha Channel. A Small Craft Advisory (SCA)
has been issued for the typically windy waters around the Big
Island and Maui tonight and expands to cover all waters for
Wednesday and Thursday as trades rapidly build. The high will be
pushed to the east by a North Pacific front late Thursday and
Friday, leading to a gradual decline in the trades. Trades may
decline further this weekend as the front passes north of the
islands.

A small northwest swell peaking this evening will be overwhelmed
by a larger northwest tonight and Wednesday. The first swell is
up to 2 to 3 feet at 17 seconds at the PacIOOS Waimea Bay buoy
this afternoon, while NOAA buoy 51001 is measuring the larger
swell around 5 to 6 feet at 14 to 15 seconds. The larger swell
will produce increasing surf tonight along exposed north and west
showers from Kauai to Maui, with waves peaking around High Surf
Advisory levels on Wednesday as the swell shifts out of the north-
northwest (330 degrees). We have held off on issuing an advisory
for now and will wait for additional data from buoy 51001. The
northwest swell will be accompanied by a small to moderate short
period north swell aimed primarily west of Kauai, while building
trades produce increased wind waves. The combined seas from all of
these sources will be in excess of 10 feet that will contribute
to the need for the SCA. The north-northwest swell will gradually
decline Thursday and Friday, with another northwest swell pushing
surf back near the advisory level Saturday.

East shore surf will be on the rise Wednesday and Thursday,
primarily from increased short period trade wind swell, though
the western end of the island chain could also experience a brief
short period north (350-010 degrees) swell of 3 to 6 feet at 10
seconds. As mentioned above, this north swell will be primarily
aimed west of Kauai, but some wrapping energy could push east
shores of Kauai near the High Surf Advisory level Wednesday. The
north swell will rapidly fade on Thursday, when peaking trade
wind swell will produce surf just below the advisory level on
east shores of all islands. East shore surf will decline through
the weekend as trades weaken over and upstream of the islands.

For south shores, tiny background south swell energy will
persist.

&&

.FIRE WEATHER...
Critical fire weather conditions not expected through the forecast
period. Gusty trades continue through Wednesday, with moderate
trades expected thereafter. Incoming moisture will keep relative
humidities above critical thresholds. Periods of heavy rain
remain possible over the Big Island through Wednesday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM HST Wednesday for Big Island
Summits.

Small Craft Advisory from 6 AM Wednesday to 6 PM HST Thursday
for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-
Kaiwi Channel-Maui County Windward Waters-Maui County Leeward
Waters-Big Island Windward Waters.

Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

&&

$$

DISCUSSION...Ahue
AVIATION...Foster
MARINE...Wroe
FIRE WEATHER...Ahue