289
FXHW60 PHFO 190119
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
319 PM HST Fri Sep 18 2026

.SYNOPSIS...
A relative decrease in shower activity in the wake of a departing
surface trough associated with the remnants of Norbert is
expected through this weekend. Moderate to locally breezy trade
winds will continue through Monday before gradually declining by
midweek. Another round of enhanced moisture will arrive by next
Tuesday, which should increase shower activity statewide.

&&

.DISCUSSION...
This afternoons visible satellite and radar imagery shows a
limited amount of shower activity relative to the past couple of
days. A surface trough associated with the remnants of Tropical
Cyclone Norbert continues to move westward as it exits the
vicinity of the state tonight. However, an upper level trough
combined with the residual moisture from Norbert has kept the
environment relatively unstable, as noted by some thunderstorms
occurring offshore earlier today, and over the Kona slopes of the
Big Island this afternoon.

An increasing trend in stability and relatively drier air will
begin this weekend, which will limit shower activity and coverage
to windward and mauka areas. Kona slopes of the Big Island may
still see some afternoon showers as well through the weekend, with
a small chance of thunderstorms upslope due to lingering
instability. However with the low confidence, have not added
thunderstorms to the forecast. Trade winds will continue to blow
out of the ENE-E direction at moderate to locally breezy speeds
through Monday, but are expected to gradually decline by midweek.

Another influx of moisture associated with the remnants of
Tropical Depression 15-E is expected to arrive by Tuesday and
potentially remain through Thursday. Precipitable water values
could reach up to 2.5" over the southeastern portion of the state
according to global models, which is above seasonal normal. A
shortwave is also expected to be within the vicinity of the
islands during this time period, which could lead to some enhanced
showers statewide.

The long term forecast will also be dependent on how models
handle the remnants of Tropical Depression 15-E. The National
Hurricane Center continues to monitor the situation, and suggests
that environmental conditions are conducive for some development
of the system next week. Given that there is plenty of time for
this forecast to change, please continue to monitor the status of
tropical cyclone development through nhc.noaa.gov, and local
weather forecasts at weather.gov/hfo.


&&

.AVIATION...
Minor changes were made to the forecast to adjust for some of the
breezier trade winds this afternoon. Otherwise, we remain in a
transition between a moist airmass with a vicinity trough to drier
trades tomorrow. Mainly VFR conditions will prevail, with the
potential for MVFR cloud decks and isolated showers to continue
passing through the region. Stronger showers will likely bring a
reduction in visibility as well, perhaps down to MVFR at times.
There is a non- zero chance for isolated thunderstorms around the
Kona slopes of the Big Island; however, chances are generally
around 15% or less and confidence remains low to add to the TAF.

Tomorrow, drier air works into the region as breezy trade winds
persist.

AIRMET SIERRA remains in effect for Kauai, Oahu, Maui, and portions
of the Big Island. This is for windward exposure mountain obscuration
near or above 2,500 ft. This may be able to be cancelled by the
next AIRMET update.

As of 300 PM HST, no other AIRMETs are in effect.

&&

.MARINE...
Trade winds will remain fresh to locally strong through at least
the first half of next week. A Small Craft Advisory is in effect
for the typical windy waters around Maui County and Big Island
through Saturday, and will likely be extended into early next week
for these waters.

Surf along south-facing shores will remain above average through
the weekend. The current long-period south-southwest swell will
peak this evening, then gradually decline through the weekend as
the next moderate, long-period south swell fills in late Saturday
through Monday, possibly nearing advisory criteria.

Moderate surf along east-facing shores will persist over the next
several days as fresh to locally strong trades continue. Surf
along north-facing shores will remain flat to tiny, with a minor
bump possible Tuesday into Wednesday next week.

&&

.FIRE WEATHER...
Fire weather risk remains low due to residual moisture from the
remnants of Norbert. The inversion is sitting roughly around 7kft,
but is expected to lower over the weekend. Moderate to locally
breezy trade winds are expected through Monday, and should filter
in some relatively drier air for that time period.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Saturday for Alenuihaha
Channel-Big Island Leeward Waters-Big Island Southeast Waters-
Maalaea Bay-Pailolo Channel.

&&

$$

DISCUSSION...DT
AVIATION...KR
MARINE...Farris
FIRE WEATHER...DT