Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 04/09/2026 12:04:00 AM UTC

                        
385
FXHW60 PHFO 081404
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
404 AM HST Wed Apr 8 2026

.SYNOPSIS...

Deepening low pressure to the west of the islands will draw up
tropical moisture from the south through the week. This will lead
to periods of heavy rainfall, thunderstorms, and an increased
flooding risk. Strong and gusty south to southeasterly winds are
also expected Thursday and Friday. Unsettled conditions could
continue through the weekend and next week as surface moisture and
instability lingers.

&&

.DISCUSSION...
Current satellite imagery this morning shows an area of low
pressure beginning to develop west of the islands. A potent upper
level trough to the northwest is currently moving southeast and
will enhance the surface trough to the west through the next few
days. Heavy showers and thunderstorms can be seen mostly around
east Maui and southeast Big Island, as well as the waters south of
Maui.

South to southeast winds will strengthen today, pulling deep
tropical moisture northward over the islands with precipitable
water values around 2". An upper level trough will also move
closer to the state and enhance large- scale lift. As a result,
widespread heavy rain is expected to gradually increase through
the day statewide. A Flood Watch is in place for all islands from
this morning through Friday afternoon. A Winter Weather Advisory
is also in effect this morning for a combination of freezing rain
and snow on the summits of the Big Island above 12,500 feet,
lasting through Friday morning.

There has been increasing focus on the need for a Wind Advisory
or a High Wind Watch beginning Wednesday night as southerly winds
begin to ramp up. These winds will be especially strong strong in
and around heavier showers and thunderstorms, and in the vicinity
of mountain ranges where downsloping gusts over northern and
windward slopes can occur. Severe wind gusts (60+ mph) look increasingly
likely with latest high resolution model runs. Late tonight
through Thursday morning could see advisory level winds over
Kauai and Oahu (30-39 mph) and then possibly high wind warning
levels (40+ mph) by Thursday afternoon through Friday morning.
Future shifts will monitor and refine the situation as the time
period approaches.

Thursday night through Friday night. Intense upper-level forcing
develops. The combination of right entrance dynamics and curved flow
will maximize upper-level divergence over the western end of the
state by Thursday evening. A mature jet-front system takes shape
west of Kauai as this forcing rapidly organizes and ramps up and
showers and thunderstorms along the frontal zone begin to
intensify. The heavy rain then surges eastward Thursday night
bringing the heaviest rainfall to Kauai late Thurs night into
early Friday, Oahu during the first half of Friday, and Maui
County and the Big Island during the second half of Friday.

High-end advisory winds are likely on the Big Island Summits and
possibly Haleakala Summit on Maui Thursday night through Friday.
Snow potential on the Big Island Summits will be limited by marginal
temperatures.

Saturday onward.
The resident band of tropical moisture will likely linger over
the islands for the foreseeable future, although a short break in
rain is anticipated by Saturday as drier air briefly moves in.
More periods of rain are possible through the remainder of the
weekend into next week as more upper level disturbances track over
the state. This may yield periods of localized heavy rain, but
that remains to be seen.

&&

.AVIATION...

Latest radar imagery continues to show rain showers affecting
mainly Maui and the Big Island early this morning. While dry
conditions prevail across the islands west of these two, some low
clouds have been observed thanks to recent rainfall and light
winds. Expect mixed conditions for most of the period as a result.
Weather models suggest another round of widespread showers is
expected to arrive around late afternoon / early evening across
the islands.

AIRMET Sierra is in effect for IFR conditions for Lanai, which has
reported ceilings as low as a couple hundred feet most of the
overnight period. This is expected to improve during the day
Wednesday, however. Mountain obscuration continues to impact
Molokai, Maui, and the southeast portions of the Big Island as
well, with some improvement expected after sunrise, before
deteriorating once again once this next round of rain arrives.

&&

.MARINE...

South to southeast winds are expected to steadily increase
late today into Thursday, as a low pressure system develops just
west of the state. A Small Craft Advisory (SCA) is now in effect
for the waters around the Big Island and the SCA will expand in
coverage tonight as the winds continue to strengthen. Showers,
some locally heavy, will be possible through Friday as a result of
the southerly winds bringing tropical moisture to the north over
the islands. As the low pressure system further deepens Thursday
into Friday, we will likely see a greater coverage of
thunderstorms and winds are expected to increase to gale force
across many coastal waters. A Gale Watch has been issued starting
Thursday for the waters around Kauai and Oahu. Depending on how
the low pressure system evolves, Gale force winds could be
possible across all Hawaiian Waters around Thursday night. Very
rough boating conditions are expected late Thursday into Friday as
seas quickly rise in response to the strong to gale force
southerly winds.

The current south-southwest swell continued to fill in overnight
and latest near-shore buoys are at around 4 feet 17 to 18 seconds
this morning. We should see this swell continue to fill in a bit
more throughout the day today and slowly drop tonight through the
rest of the week. A High Surf Advisory has is in effect for all
south facing shores of the Hawaiian Islands through tonight.

Along north facing shores, a new moderate long-period northwest
(310-320 degree) swell continues to fill in this morning and will
steadily rise throughout the day today. This swell should peak
just below advisory thresholds later today. A smaller short-period
northwest swell is expected over the weekend into early next week.

As the long-period south swell declines on Thursday, strong to
gale force southerly winds are expected to develop on Thursday
and strengthen even further Thursday night into Friday. This
increase of southerly winds will bring a rapid increase of short-
period energy Thursday into Friday and will once again bring surf
heights above the advisory thresholds for south facing shores.
Large disorganized surf is expected along many south facing shores
Thursday into Friday.

Surf along east facing shores could see an increase later this
week due to the strengthening southeasterly winds especially for
southeast exposures.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Thursday for Niihau-Kauai
Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-Kona-Kauai
South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai West-
Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central
Valley South-South Maui/Upcountry-South Haleakala-Big Island
South-Big Island Southeast.

Flood Watch through Friday afternoon for all Hawaii islands-

Winter Weather Advisory until 6 AM HST Friday for Big Island
Summits.

Small Craft Advisory from 6 PM this evening to 6 AM HST Thursday
for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Oahu Leeward Waters.

Gale Watch from Thursday morning through late Thursday night for
Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters.

Small Craft Advisory until 6 AM HST Thursday for Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Waters.


&&

$$


DISCUSSION...Tsamous
AVIATION...Evans
MARINE...Kino