Area Forecast Discussion
Issued by NWS Honolulu, HI

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105
FXHW60 PHFO 170215
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
415 PM HST Thu Oct 16 2025

.SYNOPSIS...
A relatively unstable moderate to locally breezy trade wind
weather pattern will continue into Saturday. An upper low centered
just NW of Kauai, along with low level convergent cloud bands
riding in on easterly trade winds, bring periods of showers to all
islands. Some of these showers will be locally heavy at times,
with a slight chance of thunderstorms mainly over the western half
of the state through Saturday. Enhanced showers will linger
through next week as another upper low moves in from the northeast
and lingers over the area.

&&

.DISCUSSION...
Radar and satellite show isolated to scattered showers over the
islands this afternoon. The heaviest showers have been over Kauai.
Thunderstorms have remained outside the coastal waters so far,
but there is a slight chance we could see some lightning close to,
or even on, the islands tonight. And this slight chance will
continue through Saturday.

As the upper low drifts slowly southwest and weakens over the next
few days, several rounds of increased low-level moisture will move
in from the east as trade winds continue. The latest model
guidance shows the most significant moist pushes coming in Friday
night and again Monday night. But even without these enhanced
periods, windward areas will see numerous showers over the next
few days. The best chance for thunderstorms near or on land will
be over the western islands, as they will be closer to the coldest
air aloft. Moderate to heavy rain is expected with the stronger
showers and any thunderstorms that manage to form, but conditions
are not especially favorable for flooding, and although we
continue to watch for potential changes, a flood watch is not
warranted at this time.

The first upper low will be replaced by a second one late Monday.
This next one will stall to the northeast of the state, then
weaken and move off to the east. An upper trough connecting the
remnants of the first low to our SW and the second one to the NE
will remain over the area. However, the coldest air aloft will
have moved off well to the NE, and what gets left near us will not
be cold enough to continue the threat of thunderstorms past
Saturday.

Trade winds will continue at 15 to 20 kts through at least the
middle of next week, keeping showers focused on typical windward
and mauka areas.

&&

.AVIATION...
Moderate to locally breezy trades will persist through Friday and
deliver periods of low level clouds and showers to windward and
mountain areas. The presence of an upper level low centered near
Kauai will allow some of these showers to become enhanced and
bring periods of heavy rain and possibly isolated thunderstorms.
Isolated showers can be seen moving into windward and mountain
areas this afternoon, with clouds and showers also building up
over leeward portions of the Big Island. Upstream, a band of
moisture can be seen just to the east of the island chain on
visible satellite imagery and is expected to move through this
evening into the overnight hours. As it moves through, trade wind
showers will increase in coverage and intensity and isolated
thunderstorms will be possible. Additional bands of moisture will
filter in on the trades on Friday, prolonging the unsettled
pattern. Heavier shower and storm activity will be capable of
producing MVFR and isolated IFR ceilings and visibility.

AIRMET SIERRA for tempo mountain obscuration will likely be needed
later this evening as clouds and showers increase in coverage.

AIRMET TANGO is in effect for across the island chain for tempo
moderate turbulence between FL300 and FL380. This is expected to
continue through the day.

&&

.MARINE...
Moderate to locally strong trades will remain in place over the
Hawaiian coastal waters through the forecast period. An upper low
north of Kauai is drifting southwestward today and will keep
isolated thunderstorms in the forecast over the waters into the
weekend.

Moderate, long period NW swell maintains near to above average
surf along N and W facing shores through the end of the week. A
brief moderate, long period NNW swell advances through the area on
Friday in maintenance of elevated surf and then tapers off
Saturday. Surf along N and W shores then trends down through the
weekend. A hurricane force low is forecast to develop east of
Japan later today and could bring another round of moderate, long
period northwest swell early next week.

A series of small, medium to long period south to southwest
swells filter into the area into the weekend, keeping S shores
from going flat. Short period surf along E shores picks up today
into the weekend as trades strengthen.

&&

.FIRE WEATHER...
Wind speeds and afternoon minimum humidity levels will remain
below critical fire weather thresholds this week. Unstable
conditions will produce increasing wet weather trends across the
state into Saturday. Locally heavy rain and thunderstorms are
possible during this time period. Temperature inversion heights
near Maui and the Big Island will range from the 7,500 to 9,000
feet MSL into the weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

&&

$$

DISCUSSION...Parker
AVIATION...Farris
MARINE...JVC
FIRE WEATHER...Parker