664
FXHW60 PHFO 280651
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
851 PM HST Sun Sep 27 2026

.SYNOPSIS...
Strong trades will diminish during the next 24 hours and turn
southeasterly Monday night into Tuesday. Showers increase over and
around Kauai during midweek.

&&

.SHORT TERM UPDATE...
Radar images this evening are showing trade wind showers moving
quickly mainly across Maui and north of Molokai. Rest of the state
has remained dry but breezy. Quite night with pleasant weather
conditions expected to prevail through Monday evening. Other than
the aviation section, no updates are needed to forecast package
tonight. Trade wind showers will continue to move from time to
time overnight into Monday morning.

&&

.PREV DISCUSSION...
Issued at 305 PM HST Sun Sep 27 2026

Regional satellite shows Hurricane Nolo advancing westward well
south of the Hawaiian Islands. Veered SE mid-level flow is piling up
clouds over the SE-facing slopes of the Big Island, but moisture
quality is rapidly diminishing as drier air works into the area.
Widespread light to moderate showers this morning have diminished in
coverage and mixed upslope and will eventually clear out tonight. A
band of showery low clouds aligned parallel to the trades is taking
aim on Kauai this afternoon where some enhanced coverage of showers
late this evening. However, veering mid-level winds will eventually
steer this moisture northwestward and away from the island.

Winds are diminishing as the pressure gradient over the islands
gradually eases. Select zones in Maui County and on the Big Island
are still experiencing gusts in excess of 50 mph, so the HWW has
been transitioned to a Wind Advisory that will run through tonight.
For remaining zones, wind headlines have been allowed to expire.

Attention for mid-week focuses on rainfall potential over Kauai,
particularly the south and southeast facing slopes. A band of
moisture presently on the NE side of Nolo extends southeastward into
the deep tropics per visible imagery. This band will be drawn over
Kauai Tuesday through Friday. Elevated moisture initially moves over
the island on Monday, but dry low-levels and lack of ascent preclude
an increase in pops as this likely amounts to nothing more than
increased cloud cover.

PWATs are then poised to rise from around 1" tonight to 2+" by
Monday night as rich low-level moisture characterized by dewpoints
firmly in the low 70s becomes established over the island. Weak but
deep cyclonic flow coupled with gentle ascent caused by moisture
advection will support increased showers over and around Kauai on
Tuesday. Model cross-sections indicate rapidly diminishing boundary
layer stability by late Tuesday which, combined with enhanced SE
flow around the eastern periphery of Nolo should maximize orographic
assistance. Coverage and persistence of rain is subject to some
uncertainty, but given the broad/weak ascent field and lack of low-
level forcing mechanism, suspect this will likely manifest as an
enhanced coverage of quick-moving showers from the south and
southeast. Waves of moisture advection then maintain some degree of
enhanced shower activity over Kauai through Friday, but peak forcing
and moisture depth will be late Tuesday through Wednesday with
diminishing coverage likely thereafter.

Worth noting that this moisture will lift over the remainder of
state by Wednesday perhaps supporting some increase in showers,
though taken at face value decreased SE winds in the shadow of the
Big Island and Maui may set the stage for some afternoon convection
over Oahu Wednesday through Friday, becoming more likely each day as
the gradient continues its weakening trend.

Guidance indicates the first cold front of the season reaching the
western islands early next week. Southward progress of such fronts
are generally overestimated by the models this early in the season,
but indications are that it could be rather strongly forced, so it
may nonetheless work into the area bringing with it decreased
dewpoints and a modest increase in showers.

&&

.AVIATION...
Gusty winds will continue tonight but will gradually decrease
Monday as Hurricane Nolo moves further away. Shower activity has
significantly decreased statewide, and only a few light showers
embedded within the gusty trades remain. These will favor windward
and mountain areas, but VFR conditions will prevail at most
locations.

AIRMET Tango remains in effect for moderate to isolated severe
turbulence below 9,000 feet over and immediately downwind of
island terrain.

AIRMET Tango also remains in effect for sustained surface winds
of 30 kt or greater across Maui County and the Big Island. This
AIRMET will likely be on Monday as winds decrease.


&&

.MARINE...
Issued at 305 PM HST Sun Sep 27 2026

Strong to near gale force trade winds and large, rough seas will
gradually diminish tonight and Monday as the center of Hurricane
Nolo moves northwestward roughly 275 to 325 nm south and southwest
of Kauai. During this time, high pressure far north of the state
will erode, and as Nolo moves farther west, the pressure gradient
over the islands between the ridge and Nolo will weaken and allow
the trades to ease. As a result, the Gale Warning that was in
place for all waters has been downgraded to a Small Craft
Advisory (SCA). Monday night through Tuesday night, the official
National Hurricane Center forecast calls for Nolo to move toward
the north-northwest and remain over 200 nm west of Kauai. Expect
moderate to locally strong winds to veer out of the east-
southeast to southeast during this time, requiring a SCA for
exposed waters near some islands. Winds will gradually ease and
back more easterly Wednesday and Thursday as Nolo moves westward
away from the islands.

The broad area of strong to near gale force trade winds north of
Hurricane Nolo has generated large and rough seas across the
region. This fetch of winds and east swell/seas is weakening from
east to west, and seas at the PacIOOS Hilo buoy, which have been
dropping rapidly since midnight, fell below 10 feet at midday. A
similar steep decline is anticipated at the Pauwela buoy north of
Maui this afternoon, followed by Oahu and Kauai overnight. As a
result, the High Surf Advisory (HSA) for east-facing shores of Big
Island and Maui County has been cancelled, and the HSA remains in
place for Oahu and Kauai through tonight. East shore surf will
slowly decline Monday through Wednesday, though small, medium-
period swells from distant east Pacific hurricanes will maintain
moderate surf during the remainder of the week.

A mix of long to medium period south-southwest swell and building
short to medium period south swell from Hurricane Nolo will keep
surf along south facing shores elevated during the next couple of
days. The longer period swell alone would produce surf near
seasonal average, but the hurricane swell may push heights to the
HSA level Monday. Given uncertainty, we will have held off on
issuing an advisory for now, even though we are forecasting HSA
level surf Monday. As Nolo makes a turn toward the north-
northwest, the likelihood of advisory level surf from the shifting
southwest swell will increase late Monday and Tuesday, especially
across Kauai and Oahu. By Wednesday, the swell will switch out of
the west.

On north facing shores, a small medium period swell will maintain
small surf through Monday, followed by a decline Tuesday. Some
wrapping west swell from Hurricane Nolo is possible by Wednesday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 AM HST Monday for Big Island North-Central
Oahu-East Honolulu-Honolulu Metro-Kipahulu-Kohala-Koolau Leeward-
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-Oahu North Shore-
South Haleakala.

High Surf Advisory until 6 AM HST Monday for Kauai East-Kauai
South-Koolau Windward-Olomana.

Small Craft Advisory until 6 PM HST Monday for Alenuihaha
Channel-Big Island Leeward Waters-Big Island Southeast Waters-
Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai
Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters-Maui
County Leeward Waters-Maui County Windward Waters-Oahu Leeward
Waters-Oahu Windward Waters-Pailolo Channel.


&&

$$

DISCUSSION...Castro
AVIATION...Vaughan
MARINE...Quesada