Flash Flood Warning 49, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
805 AM HST Mon Sep 7 2026

.SYNOPSIS...
Winds will veer to the east-southeast and strengthen as Hurricane
Lowell approaches. The center of Lowell is forecast to pass west
of of Kauai tonight, but close enough that a Hurricane Warning is
in effect for Kauai and Niihau and a Tropical Storm Warning is in
now place for Oahu. High surf and heavy rain will impact all
islands with strong winds mainly impacting the western end of the
state.

&&

.DISCUSSION...
Hurricane Lowell is about 325 statute miles southwest of Kauai
this morning moving north northeastward. Lowell's track has
shifted eastward closer to Kauai and Niihau with advisory updates
this morning, and the core of Lowell is expected to pass west of
the Kauai. This has again has raised the possibility of hurricane
force winds reaching Kauai and Niihau and Tropical Storm force
winds reaching Oahu, as a result a Hurricane Warning has been
issued for Kauai and Niihau. A Tropical Storm warning is also in
place for Oahu due to this eastward shift. On satellite imagery
this morning, a band of heavy rain with some embedded thunder is
approaching south of the Big Island's southeast slopes. We will be
monitoring the progression of this rain band among many other
things.

Additional impacts from Lowell are expected statewide, and a few
headlines are in effect as a result. A High Surf Warning for south
facing shores for the south swell generated by Lowell for all
islands, along with the west facing shores of the Big Island. A
High Surf Advisory remains in effect for the east swell generated
by former Tropical Storm Karina, which has weakened to a post
tropical low. For surf and other marine impacts, please see the
marine section of the discussion below.

The Flood Watch for the state continues through Tuesday due to
heavy rain brought in by Lowell and associated rain and
thunderstorm bands. Terrain influence will play a big factor with
isolated areas receiving significant amounts through the event.
Stay alert for the issuance of any future flood advisories or
warnings across the state. See hydrology section for additional
information.

The threat of short-lived, fast-moving tornados/waterspouts will
be present mainly near Kauai and Niihau as Lowell makes its
closest approach to the islands. These would likely be embedded in
rainbands. The threat for tornadoes is lower near the remaining
islands, but not zero. The threat for tornadoes should decrease
quickly early Tuesday morning.

Any deviation in track or intensity could also change how these
hazards effect the islands.

High pressure is forecast to build back in Thursday through
Saturday, bringing in a more typical trade wind pattern. Moisture
may take a bit longer to exit the area as well, so conditions are
expected to dry out more gradually into the weekend.

&&

.AVIATION...
Hurricane Lowell continues its track northward, advecting unstable
deep tropical moisture northward into the islands. Shower
activity will continue to trend higher into Tuesday. MVFR
conditions with low cloud ceilings and showers are expected
statewide. Heavier showers will produce periods of IFR
conditions. Surface winds will strengthen today over the western
half of the state, as Hurricane Lowell continues on a northern
track.

AIRMET Sierra for mountain obscuration continues for Kauai Oahu
Molokai Maui and the Big Island. This AIRMET will likely continue
into Tuesday.

AIRMET Tango was issued for moderate low level turbulence
affecting the island of Kauai over and SW thru NW of island
mountains. A strong surface wind AIRMET will likely be issued for
Kauai and Niihau later today for wind speeds greater than 30
knots due to Hurricane Lowell approaching the islands.

Light icing continues in a layer between 160 and FL220 due to
strengthening low level wind speeds as Lowell approaches the
island.

&&

.MARINE...

Hurricane Lowell, located southwest of the islands, continues to
move north-northeast this morning. As it approaches the island
chain wind speeds will increase. A Hurricane Warning remains in
effect for waters west of Kauai County, while a Tropical Storm
Warning remains in effect for Kauai Channel and Kauai Windward
Waters through Tuesday afternoon. A slight eastward shift in the
track has also prompted the issuance of Tropical Storm Warnings
for Oahu Leeward and Windward Waters. The Small Craft Advisory
remains in effect for all remaining coastal waters for a
combination of winds and seas through Tuesday. Winds are expected
to increasingly veer to the southeast to south as Lowell
approaches and the strongest winds and highest seas are expected
for the western end of the state.

Hurricane conditions are expected in the western offshore waters
as Lowell through Tuesday as the center of the storm tracks just
west of Niihau. Any slight deviation in the track to the west or
east in the next 24 hours will have significant differences in
impact for the coastal waters around Kauai County. Post-Tropical
Cyclone Karina to the northeast of the islands will continue to
weaken and dissipate later today.

South-southwest swell from Hurricane Lowell will rapidly build today.
As a result, surf along south facing shores will begin to rise from
advisory levels this morning to warning levels by this afternoon and
peak overnight. The swell will increasingly shift out of the
southwest tonight. Due to the track of Lowell west of the main
islands, a sharp gradient in swell is expected from west to east. This
will bring damaging surf to portions of Kauai County and possibly
Oahu. Coinciding also with the peak monthly afternoon high tides,
this could bring the potential for significant damage to coastal
properties and infrastructure, including roadways to portions of
Kauai and possibly Oahu. Swell energy is expected to rapidly
decline on Tuesday.

A moderate, long-period south swell also arrives today and peaks
overnight into Tuesday, but will be overwhelmed by the larger
swell from Hurricane Lowell. Although it begins to fade on
Tuesday, it will keep south shore surf somewhat elevated through
Thursday. A large, medium-period east swell from former Tropical
Storm Karina will combine with increasing east to southeast wind
wave generated by Hurricane Lowell to keep advisory level surf
along east facing shores through Tuesday. Surf along north facing
shores will also experience a small increase on Tuesday as Lowell
lifts north of the island chain and then fade through the week.

&&

.FIRE WEATHER...
Fire weather risk will remain low through the forecast period due
to increasing moisture moving over the islands in association
with Hurricane Lowell. Thunderstorms will be possible through
through tonight to the unstable airmass moving overhead.
Temperature inversion heights are expected to remain elevated or
non-existent during the next few days.

&&

.HYDROLOGY...
The potential for flooding exists through Tuesday, and as a
result, a Flood Watch is in effect for the entire state. It is
possible the watch may need to be extended into Tuesday night or
Wednesday depending on the lingering rain bands across the state
in the wake of Lowell as guidance suggests. However, will hold off
any update to the watch at this time.

Hurricane Lowell is expected to bring additional rain to the
islands through Wednesday morning with 6 to 10 inches, isolated
16 inches across Kauai. Oahu and Maui County, 4 to 8 inches,
isolated 10 inches. Big Island, 4 to 8 inches, isolated 12 inches.
This rainfall may produce significant flash flooding and
mudslides, especially across Kauai County and south and east
portions of the Big Island. Its important to note that any pop up
thunderstorms that develop could dramatically increase total
rainfall amounts anywhere.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Tuesday afternoon for all Hawaii islands-

High Surf Warning until 6 PM HST Tuesday for Niihau-Kauai
Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-Kona-Kohala-
Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai
Southeast-Molokai West-Molokai Leeward South-Lanai Leeward-Lanai
South-Maui Central Valley South-Kipahulu-South Maui/Upcountry-
South Haleakala-Big Island South-Big Island Southeast.

Hurricane Warning for Niihau-Kauai-

Tropical Storm Warning for Oahu-

High Surf Advisory until 6 PM HST Tuesday for Olomana-Kauai East-
Koolau Windward-Molokai Windward-Windward Haleakala-Big Island
East-Big Island North.

Hurricane Warning for Kauai Northwest Waters-Kauai Leeward
Waters.

Tropical Storm Warning for Kauai Windward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters.

Small Craft Advisory until 6 PM HST Tuesday for Kaiwi Channel-
Maui County Windward Waters-Maui County Leeward Waters-Maalaea
Bay-Pailolo Channel-Alenuihaha Channel-Big Island Windward
Waters-Big Island Leeward Waters-Big Island Southeast Waters.

&&

DISCUSSION/HYDRO/FIRE WEATHER...Tsamous
AVIATION...Bohlin
MARINE...Quesada