519
FXHW60 PHFO 060257
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
457 PM HST Sat Sep 5 2026

.SYNOPSIS...

Breezy east-northeast trade winds will gradually veer to the east
and then east-southeast this weekend into the upcoming week as
Hurricane Lowell approaches from the southwest. Lowell is
forecast to pass west of Kauai`s coastal waters as a category 2 or
3 Hurricane and a Tropical Storm watch is in effect for Kauai and
Niihau. Impacts such as high surf and heavy rain are forecast to
extend hundreds of miles from the center, potentially impacting
any of the islands.


&&

.DISCUSSION...

Radar and satellite imagery this afternoon shows a wetter that
normal summertime trade wind pattern with scattered to numerous
showers over windward and mountain areas. Increasing moisture
upstream is also evident and will contribute to increasing showers
this evening into tomorrow. Weather conditions then deteriorate
Sunday evening into the upcoming week.

Hurricane Lowell is currently sitting about 620 statute miles
southwest of Kauai moving west-northwest at 4 kt as a category 4
(130 mph maximum sustained winds). Lowell is forecast to continue
its northerly track and move slightly northeast tomorrow through
Monday. It`s forward speed will increase over the next 2 days and
it will make its closest approach to the main Hawaiian Islands
Monday night as a category 2 to 3 hurricane. Lowell is forecast to
pass west of Kauai`s coastal waters, and will bring several
hazards to the state. The main hazards are expected to be flash
flooding, strong southerly winds, and high surf. A Tropical Storm
watch is in effect for Kauai and Niihau and its associated waters.

The greatest risk for flooding at this time appears to be Sunday
evening through Tuesday morning, and could potentially linger into
Wednesday, as deep tropical moisture associated with Lowell is
drawn up from the south. The environment will begin destabilizing
Sunday afternoon as CAPE values and moisture depth increase. The
winds will also veer to the east- southeast and increase starting
Sunday evening. As of this forecast package, the islands of Kauai
and Niihau are expected to receive the highest rain totals,
however the threat of heavy rainfall and thunderstorms will be
present anywhere in the state, and flooding could occur as a
result. Heavy showers and thunderstorms that develop will likely
be disorganized. Therefore everyone in the state should be
prepared for flooding. A flood watch is in effect statewide from
Sunday evening through Tuesday.

Winds will increase and veer out of the east-southeast by Sunday
night into Monday morning with Kauai County having the strongest
winds. Winds will also increase out of the southeast for the rest
of the islands to a lesser extent, and could be amplified by
island terrain.

The threat of short-lived, fast-moving waterspouts will be
present mainly near Kauai and Niihau as Lowell makes its closest
approach to the islands. These waterspouts would likely be
embedded in squally rainbands that would be tornadic if they come
ashore. This is due to the islands proximity to Lowell`s east
side, where low level shear and instability will increase as the
center of circulation passes west of Kauai. On Monday, 0-1 km
shear increases to 20-25 kt or more on Kauai and Niihau, and 0-1
km SRH increases for a time to 200-300 m2/s2 in the RRFS. The
threat appears quite a bit less for the other islands, though non-
zero in any downwind convergence zones peeling off the islands.
This threat should decrease quickly early Tuesday morning.

For surf and other marine impacts, please see the marine section
of the discussion below.

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 drier and more stable conditions. Long range
models then indicate a tropical wave potentially moving over the
islands next Sunday into Monday, although confidence is very low
this far out.


&&

.AVIATION...
Moisture within a moderate to locally fresh easterly trade wind
flow will produce MVFR conditions over most windward slopes
through tonight, while VFR will prevail leeward. AIRMET Sierra for
mountain obscuration now covers north through east facing areas
from Kauai to Maui, and Big Island may need to be added by
evening. AIRMET Tango remains in effect for low-level mod turb
over and south through west of all island mountains, but this
AIRMET may be dropped as early as this evening as winds drop
slightly and the inversion weakens.

Expect winds to decrease only slightly and veer more easterly on
Sunday. The atmosphere will slowly destabilize through the day,
and deepening moisture along the far periphery of Hurricane Lowell
may overspread the state and lead to isolated heavy showers and
thunderstorms in the afternoon.


&&

.MARINE...

A surface high north of the Hawaiian Islands and will slowly
drift east through the weekend. Currently, Hurricane Lowell is
around 540 nm south-southwest of Kauai as it moves to the west-
northwest. The trade winds have continued to gradually ease
through the day, and therefore the Small Craft Advisory (SCA) has
been cancelled. Lowell is expected to turn more northward on
Sunday, which will cause winds across the coastal waters to veer
to the southeast to south with the strongest winds across the
western end of the state. A Tropical Storm watch is in effect for
Kauai and Niihau and its associated waters.

Based on the latest advisory from the National Hurricane Center,
hurricane conditions are expected in the offshore waters west of
160W by Sunday night and lingering through Tuesday as it tracks
north. While confidence is increasing in the track forecast of
the cyclone, any slight deviation in the track to the west or
east from the current predicted path will have significant
differences in impact for the coastal waters around Kauai County.
As for Tropical Storm Karina, it is expected to weaken and
dissipate as it moves northeast of the state.

Southerly swell generated by Hurricane Lowell will keep surf along
south facing shores at High Surf Advisory criteria through at
least Sunday. As Lowell begins to turn more north, its swell will
gradually veer from south to southwest and begin a rapid upward
trend. Very large surf exceeding warning criteria appears
increasingly likely for south and west facing shores by Monday.
Coinciding also with monthly high tides, this will create the
potential for impacts to harbor entrances, channels, as well as
vulnerable coastal properties and infrastructure including
roadways. Surf will then rapidly decrease on Tuesday after the
hurricane passes north of the island chain. A pulse of
northwesterly swell could then bring a minor bump to north shore
surf on Monday night into Tuesday and fade through Thursday.

East facing shores will see continued advisory level surf from a
large, medium-period east swell generated by Tropical Storm
Karina to the east of the islands. This swell will gradually fade
early next week as Karina weakens. Late next week, surf along
east facing shores could be bolstered by some medium-period swell
generated by Hurricane Marie in the East Pacific. Otherwise,
expect choppy conditions from easterly trade wind swell through
the week.


&&

.FIRE WEATHER...

Fire weather risk will remain low through the forecast period due
to increasing moisture associated with Hurricane Lowell. The
temperatures inversion heights are currently near 8,000 ft, and
are expected to become elevated during the next few days.


&&

.HYDROLOGY...

Heavy rain looks likely Sunday evening through potentially
Wednesday, depending on how long the moisture lingers in the area.
Storm total rainfall estimates range from 2 to 8 inches
statewide. Locally higher amounts (around 12+ inches) are possible
for Kauai due to its proximity to Lowell. It is important to note
that heavy showers or thunderstorms could develop anywhere,
bringing intense rain rates and significantly raising storm total
rainfall amounts. A flood watch is in effect statewide from
Sunday evening through Tuesday.




&&

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

Tropical Storm Watch for Niihau-Kauai-

Flood Watch from Sunday evening through Tuesday afternoon for
all Hawaii islands-

Tropical Storm Watch for Kauai Northwest Waters-Kauai Windward
Waters-Kauai Leeward Waters-Kauai Channel.


&&

$$


DISCUSSION...Tsamous/R Ballard
AVIATION...Wroe
MARINE...Farris
FIRE WEATHER...Tsamous