Wind Advisory 1, NWS Honolulu, HI

Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
422 AM HST Fri Jan 31 2025

.SYNOPSIS...
The main rain shield leading a front passing into the central
islands has shifted over eastern Maui and Big Island early this
morning. This shield still contains pockets of heavy showers and
isolated thunderstorms and will shift east over Big Island this
morning. There still be intense rainfall rates within the
strongest cells that are capable of producing localized flash
flooding. Strong westerlies are also still possible as this area
of rain and the trailing cold front passes across Big Island
through the day. Conditions will gradually across the state from
west-to-east as cooler, drier air fills in behind the front this
weekend. Cooler and breezy trade wind weather is expected through
the first half of next week.

&&

.DISCUSSION...
The eastern half of the state and surrounding coastal waters
remains within the warm sector of a 989 mb storm force low that is
positioned about 570 miles north of Lihue, Kauai, at 4 AM HST
this morning. Moderate layer southwesterly winds still persist
over the region as evidenced by local island radar VADs.
Communities just downstream of north and east-facing terrain will
still experience downslope accelerations, in addition to any
passing convective downdrafts, will produce breezy conditions.
The wind threat will remain unchanged for primarily Big Island
today. The High Wind Warning (HWW) remains in effect for Haleakala
and the Big Island through the afternoon. Veering weakening winds
to the west northwest over the western two thirds of the state
will lower HWW down to a Wind Advisory for the remaining lower
elevation zones and islands of Maui County. The cold front is
passing across the western third of the state (as of this
writing). The front is expected to fall apart over the eastern
third of the state (or around Big Island) in response to weakened
forcing and the influx of a drier, post frontal air mass.

Due to the progressive nature of the rain, the main near term
thunderstorm threat will be from localized wind gusts up to and in
excess of 60 mph across Big Island this morning. Recent rain
episodes of rain rates of 1 to 4" per hour rates over Oahu
induced the flooding of many roads and low-lying areas while
producing some minor flooding along various streams yesterday.
The latest deterministic, global scale guidance indicates that the
greatest mid-level instability will continue shifting east Big
Island during the day. Higher resolution modeling propagates the
highest QPF quickly eastward onto Big Island by sunrise, holding
it up there through the day. Thus, convection is still expected to
migrate eastward and will refocus heavy rain over more leeward
areas of eastern Maui and Big Island for the remainder of the
morning.

High resolution model guidance is depicting that the heaviest rain
activity will shift east of Maui and onto Big Island this morning,
but the larger scale models paint the picture of the greatest mid
layer moisture/tightest instability gradient not moving, or remaining
anchored over east Maui and vicinity the next few hours. These
inconsistencies hold onto higher chances of a slowing line near or
over Big Island that could create a prolonged flooding threat into
the early afternoon. This outcome would delay the onset of heavy
rain over Big Island and the snow over the summits until later
this morning and afternoon. The instability gradient shifts over
the Big Island late today as low pressure pulls away and overall
forcing diminishes their flash flood threat.

Pleasant, dry post-frontal air filters in over Kauai and Oahu
going into the weekend as trade winds return.

&&

.AVIATION...
Widespread heavy showers and strong thunderstorms associated with
a cold front will continue to impact the eastern end of the state
today. Expect localized strong turbulence, minimal visibility,
and low ceilings during this period. While the threat of heavy
showers and thunderstorms will diminish over the western portion
of the state behind the front, periods of MVFR ceilings and
visibilities in light to moderate showers, along with gusty
westerly winds, will be possible, particularly over Kauai.

AIRMET Sierra is in effect for IFR conditions over Maui and the
leeward side of the Big Island this morning, which may persist
through a good portion of the day. Additionally, AIRMET Sierra
remains in effect for temporary mountain obscurations above 2,000
feet over the western end of the state.

AIRMET Tango is posted for temporary moderate turbulence below
10,000 feet and from FL260 to FL400 across the entire state.
Strong sustained winds and downsloping gusts are expected along
the north and east sides of the islands, warranting an AIRMET for
sustained winds of 30 knots or greater. Light icing is anticipated
between 14,000 feet and FL240.

&&

.MARINE...
A cold front over the islands, associated with strong low
pressure passing to the N, will continue to move E through tonight
before stalling and dissipating near the Big Island Saturday.
Impactful weather, in the form of strong thunderstorms, wind
gusts near 50 kt, and zero visibility in areas of blinding rain
will affect waters around Maui and the Big Island through at least
the morning hours. A Gale Warning is posted for select waters
around the Big Island due to frequent wind gusts well over 34 kt.
A Small Craft Advisory is posted for remaining waters. T

Moderate to locally strong fresh W to NW winds with improving
weather trends will spread from NW to SE over the chain over the
next 24 hours. Moderate to locally strong NE trade winds will
develop by Sunday as high pressure builds far NW of the islands.

A medium- to long-period N swell will persist today, then
gradually diminish, and a High Surf Advisory is posted for N
facing shores of nearly all islands. Additionally, the powerful
low passing N of the islands has produced a shorter-period NW
swell that will build today, and may maintain high surf along
north facing shores into Saturday before diminishing. Locally
generated wind waves out of the S and W will gradually diminish
through tomorrow. Another N swell will arrive Sunday and peak
Monday, producing high surf along N facing shores. A couple
moderate sized WNW swells are also expected, with a smaller one
this weekend, and a slightly larger one from Monday into Wednesday.

&&

.FIRE WEATHER...
Critical fire conditions are not expected during the forecast
period.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening for Niihau-Oahu
North Shore-Olomana-Maui Windward West-Kauai North-Kauai East-
Koolau Windward-Molokai Windward-Molokai North-Maui Central
Valley North-Windward Haleakala-Big Island East-Big Island North.

Flood Watch through this afternoon for Maui Windward West-Maui
Leeward West-Haleakala Summit-Kona-Kohala-Big Island Interior-
Maui Central Valley North-Maui Central Valley South-Windward
Haleakala-Kipahulu-South Maui/Upcountry-South Haleakala-Big
Island South-Big Island Southeast-Big Island East-Big Island
North.

High Wind Advisory through Noon today for Maui Windward West-
Maui Leeward West-Maui Central Valley North-Maui Central Valley
South- Windward Haleakala-Kipahulu-South Maui/Upcountry-South
Haleakala.

High Wind Warning until 6 PM HST this evening for Haleakala
Summit.

High Wind Warning until noon HST today for Kona-Kohala-Big
Island Interior-Big Island South-Big Island Southeast-Big Island
East-Big Island North.

High Wind Warning until 6 AM HST Saturday for Big Island Summits.

Winter Storm Warning until 6 AM HST Saturday for Big Island
Summits.

Small Craft Advisory until 6 PM HST this evening 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-
Maalaea Bay-Pailolo Channel-Big Island Windward Waters-Big
Island Southeast Waters.

Gale Warning until noon HST today for Alenuihaha Channel-Big
Island Leeward Waters.

&&

DISCUSSION...Blood
AVIATION...Gibbs
MARINE...Birchard
FIRE WEATHER...Blood

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