Flash Flooding and High Wind in Hawaii, March 12 to 15, 2026

Area Forecast Discussion
National Weather Service Honolulu HI
402 AM HST Thu Mar 12 2026

.SYNOPSIS...
A powerful kona storm will produce periods of hazardous weather
impacts across the Hawaiian Islands through the weekend. Expect
a combination of threats ranging from significant flash flooding,
damaging winds, snow and ice over the highest Big Island summits
and strong to severe thunderstorms. The strongest southwesterly
winds from Friday to Saturday will produce damaging wind gusts
along north and east of the island mountains. Unsettled wet
weather conditions with southwesterly winds will continue into
early next week. The kona storm begins to lift northward on
Monday, and unsettled weather will start to ease across the Hawaii
region. High pressure will build back in north of the state
allowing trade winds to return from next Wednesday onward.

&&

.DISCUSSION...
Moderate to heavy showers continued to pulse through the islands
last night through the early morning hours. Brief thunderstorms
were observed over portions of northern Oahu and over marine
coastal areas through the night. The latest morning satellite
water vapor imagery continues to show a complex and large upper
low set up across the Central Pacific basin. Smaller short wave
troughs are rotating counterclockwise around this larger central
low.

A brief respite in the flooding and thunderstorm threats last
night will change later today as another weak, negatively tilted,
short wave trough moves over the islands from the late morning
through the afternoon hours. The negative tilt on this upper
trough will produce more efficient atmospheric lifting dynamics,
leading to heavier showers and higher potential for strong
thunderstorm activity. Increasing trends in moderate to heavy
showers and thunderstorms will continue into the overnight hours
as a stronger negatively tilted short wave trough moves into the
islands.

The threat for Flash Flooding will continue into the weekend due
to both saturated soil conditions that more easily lead to ground
runoff and flooding from even more moderate continuous rainfall
rates. The highest flood threats across the state will favor
southern and western slopes of all islands. These are typically
the drier sides of the islands, less accustomed to heavy rain and
flooding. Driving under these heavy shower bands will become
challenging with ponding of water on area roadways. A Flood Watch
continues for all Hawaiian Islands into Saturday, this Flood
Watch may need to be extended in time as the heavy rainfall threat
may linger into Sunday.

By Friday, the weather conditions become vastly more severe, as
stronger southwesterly winds providing damaging wind gusts along
island mountain slopes, favoring northern and eastern slopes of
steep mountain terrain. Already saturated ground conditions and
trees unaccustomed to southwest winds will fall and likely cause
blocked roadways and lead to power outages. These strong southwesterly
winds will continue through Saturday afternoon. These stronger
southwest winds speed up into the 50 to 70 MPH range around the
5,000 foot level. These winds will also converge at the lower
levels, lifting the atmosphere and producing strong convective
heavy shower and thunderstorm bands. As these clouds reach higher
and higher heights in the atmosphere they will reach up and pull
down these stronger winds to the surface, yielding wind gusts in
the 50 to 70 mph range in the strongest thunderstorm cells. This
means even outside of terrain enhancing wind gusts any strong
thunderstorms are capable of producing severe hurricane force wind
gusts over islands or coastal waters through Saturday. A High
Wind Watch remains in effect to cover these damaging wind threats.

Some of these stronger thunderstorms will likely become severe
with the heaviest rainfall rates and strong damaging winds. High
levels of instability, wind shear and atmospheric forcing
ingredients are all coming into focus over the islands from
Friday through Saturday for a potential severe weather event. A
Severe Thunderstorm Watch may be needed during the Friday through
Saturday time period. However, we will likely wait until we see
these severe thunderstorm developing over the local area before
pulling the trigger on this Severe Thunderstorm Watch with a short
lead time measured in hours.

From Saturday night to Sunday another upper level short wave
trough passes over the islands leading to another upward pulse in
moderate to heavy shower activity. Thunderstorms will also
threaten the islands and become more of a flooding threat as
decreasing upper level and surface wind speeds diminish the
damaging wind gust threats.

Monday and Tuesday, the large kona storm begins to lift northward
drifting slowly away from the Hawaiian Islands. This means wet
weather continues, however moderate to heavy rainfall rates will
decrease and southwest winds will gradually weaken through the
first half of next week.

By Wednesday, the latest long range guidance shows a high pressure
system building back into position just north of the island chain,
allowing a return to a typical trade wind weather pattern with
more typical brief passing showers over windward mountain areas.

&&

.AVIATION...
Shower activity will be on the increase this morning as the next
wave of moisture moves in from the south. Showers and isolated
thunderstorms will produce MVFR conditions for many areas with
periods of IFR and LIFR conditions at times. Forecast still
remains on track for prolonged periods of heavy rainfall starting
over the western half of the state tonight. This will likely lead
to widespread IFR/LIFR conditions tonight and continuing through
Friday.

AIRMET SIERRA remains in effect for mountain obscuration for all
of Kauai, Oahu and Maui Counties.

AIRMET ZULU will be needed by later this morning as deeper
moisture moves in from the south, which should allow for some
light icing. At the same time, upper level turbulence will also
be increasing, and AIRMET TANGO will also be needed for the mid to
upper levels.

&&

.MARINE...
A powerful kona storm will continue to bring heavy rain,
thunderstorms, and rough seas to the Hawaiian islands and adjacent
coastal waters through the rest of the week. Southerly winds will
strengthen tonight into the weekend, possibly reaching gale-force
for portions of the area by Friday. A Gale Watch has been issued
for the coastal waters around Kauai and Oahu starting Friday
morning. These strong to gale- force winds will last into the
weekend in association with a band of heavy showers and
thunderstorms pushing eastward across the forecast area.

A series of small, short to medium period west-northwest swells
will bring small surf to north and west facing shores through the
rest of the week. Kauai will block some of this swell energy from
reaching Oahu and Maui, but it will make it into the west facing
shores of the Big Island. The current swell will gradually
diminish later today before the next west-northwest swell builds
Friday into the weekend. Additionally, a small, medium period
north swell originating from Alaska Peninsula gap winds is
expected to arrive tonight and continue into the weekend.

The southerly wind direction will contribute to rough and choppy
surf along south-facing shores. These south winds will intensify
tonight into Friday, causing south shore surf to build Friday into
the weekend, likely reaching advisory levels. Once southerly
winds diminish early next week, a small to moderate, long-period
south swell generated by a gale force low east-southeast of New
Zealand will arrive along south-facing shores and build into
midweek.

Choppy surf along east-facing shores will continue to trend
downward and remain below seasonal levels as south to southeast
winds prevail.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday afternoon for all Hawaiian Islands

High Wind Watch from this evening through late Saturday night
for Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, and Maui.

High Wind Watch from this evening through Sunday afternoon for
Haleakala Summit and the Big Island Summits of Mauna Kea and Mauna
Loa.

High Wind Watch from Friday morning through late Saturday night
for the lower slopes of the Big Island.

Winter Weather Advisory until 6 PM HST this evening for Big
Island Summits of Mauna Kea and Mauna Loa above 12,000 feet
elevation.

Winter Storm Watch from this evening through Saturday afternoon
for Big Island Summits of Mauna Kea and Mauna Loa above 12,000 feet
elevation.

Gale Watch from this evening through late Friday night for Kauai
Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-
Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters.

&&

DISCUSSION...Bohlin
AVIATION...Kino
MARINE...Farris