392
FXHW60 PHFO 170201
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
401 PM HST Wed Sep 16 2026

.SYNOPSIS...

Breezy trades expected through the middle of next week. An upper
level trough and moisture associated with the remnants of Norbert
will fill in across the state from east to west Thursday into
Friday, increasing the chances of heavy rain, isolated
thunderstorms, and flash flooding, especially for the windward and
mauka areas. Drier air will move back in this weekend behind the
departing trough. Moisture from the remnants of Tropical
Depression 15-E may bring another round of enhanced trade showers
around next Tuesday and Wednesday.


&&

.DISCUSSION...

Afternoon satellite imagery shows an upper level low around 1400
mi north- northeast of the islands with a trough extending
southwestward. Isolated light showers continue to move westward
with the greatest coverage from Maui northward. Trade winds will
continue to strengthen through the afternoon as the upper trough
approaches.

The upper level trough will dig southwest tonight into Thursday,
pulling in remnant moisture from Norbert. Satellite imagery shows
a broad area of precipitable water in excess of 2" beginning to
move into the Big Island, and is forecast to move across the
remaining islands tonight into Thursday. Deeper moisture and
increasing instability will bring moderate to locally heavy
showers and a slight chance of thunderstorms, with the highest
threat of thunderstorms across the Big Island Thursday afternoon.
Heaviest rain is expected on the windward and mauka areas. With
soil moisture likely still high from previous heavy rain events,
there is an increased risk of flash flooding where heavier showers
and thunderstorms occur.

Moisture will decrease from east to west late Friday through the
weekend. There is the potential for another round of increasing
moisture from the remnants of tropical depression 15-E moving
into around Tuesday to Wednesday of next week. Ensembles show at
least a weak low-level wave associated with this moisture, though
further aloft only 6% of the ensemble members have some form of
troughing while the remainder keep us under a ridge, limiting the
potential for heavier showers.


&&

.AVIATION...


Moderate to locally breezy trade winds will strengthen to breezy
levels this afternoon and a trough will approach the area from
the east. Showers and low clouds associated with that trough will
increase with the trade wind flow from east to west starting
early tonight for the eastern half of the state, then spread west
late tonight into tomorrow morning. More widespread MVFR
conditions will be possible as the moisture associated with the
trough moves in, especially for windward and mountain areas.

No AIRMETs are currently in effect. There is the possibility for
AIRMET Tango during the afternoon once trade winds strengthen.
There is also potential for AIRMET SIERRA later today as clouds
increase on the windward slopes.


&&

.MARINE...

A broad trough, associated with the remnants of Tropical Storm Norbert,
will approach the state from the east tonight, allowing moderate
to locally strong northeast trades to hold through tonight. This
afternoon ASCAT pass showed borderline Small Craft Advisory (SCA)
conditions around Maui County and the Big Island leading to less
confidence that SCA conditions will hold as the trough passes over
the state Thursday, thus have not extended the SCA at this time. After
the trough moves through the state Thursday into Friday, a
surface high far northeast of the state could allow moderate to
locally strong trades to return over the weekend through the
forecast period. Above normal moisture and upper level support
will allow isolated thunderstorms with localized heavy rain and
gusty outflows to develop over the offshore waters tonight through
Saturday.

A series of long to medium period south-southwest to south swells
will continue fill tonight. Surf along south facing shores should
begin to see more consistent sets tonight into Thursday as build
to near average. A reinforcing southerly swell will fill in Friday
bumping surf near High Surf Advisory thresholds by this weekend
as swells shift more out of a south direction.

Surf along east- facing shores increases today into Thursday as
trade winds strengthen and a small, medium- period east swell from
the remnants of Norbert arrives. Flat to tiny surf along north
facing shores is expected through the forecast period.


&&

.FIRE WEATHER...
Issued at 400 PM HST Wed Sep 16 2026


Fire weather risk should remain low through the remainder of the
week due to moderate to breezy winds and increased relative
humidity and moisture from the remnants of Norbert. Showers will
dramatically increase late tonight through early Friday.
Inversion heights will be around 7,500 to 8,500 ft.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late Thursday night for Big Island East-Big
Island Interior-Big Island North-Big Island South-Big Island
Southeast-Big Island Summits-Central Oahu-East Honolulu-Ewa
Plain-Haleakala Summit-Honolulu Metro-Kahoolawe-Kauai East-Kauai
Mountains-Kauai North-Kauai South-Kauai Southwest-Kipahulu-
Kohala-Kona-Koolau Leeward-Koolau Windward-Lanai Leeward-Lanai
Mauka-Lanai South-Lanai Windward-Maui Central Valley North-Maui
Central Valley South-Maui Leeward West-Maui Windward West-
Molokai Leeward South-Molokai North-Molokai Southeast-Molokai
West-Molokai Windward-Niihau-Oahu North Shore-Olomana-South
Haleakala-South Maui/Upcountry-Waianae Coast-Waianae Mountains-
Windward Haleakala.

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


&&

$$

DISCUSSION...SS
AVIATION...Phillips
MARINE...Almanza
FIRE WEATHER...SS

NWS HFO Office Area Forecast Discussion