Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 10/16/2026 11:01:00 AM UTC

                        
902
FXHW60 PHFO 160101
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
301 PM HST Thu Oct 15 2026

.SYNOPSIS...

A high pressure system far northwest of the Hawaiian Islands will
slowly drift from west to east over the next few days. This
passing system will increase easterly trade winds into the
moderate to breezy range lasting into the middle of next week.
Brief pulses of enhanced showers are forecast with three passing
easterly waves during this time period. Increasing shower trends
will favor the windward mountain areas in the overnight to early
morning hours starting Friday night and lingering into Tuesday
morning. The strongest of these three waves will pass through the
islands from late Sunday through late Monday.


&&

.DISCUSSION...
Radar showed scattered windward and mauka showers over each island
this afternoon, with additional Kona showers developing. Northeast
trade winds were a little stronger than yesterday, averaging 10
to 20 mph with gusts 20 to 30 mph fairly common.

A large surface high continues to strengthen to our north. Aloft,
a weak upper level low to our east will become a trough that
stretches from southern CA all the way out to us. The trough will
be weak, and apart from a slight increase in instability, we won`t
see much from it.

Several impulses of increased moisture will move west toward and
over the state, especially the eastern end, over the coming week.
The first will move through Friday afternoon and evening, and
reach all islands. We have continued the trend of the previous
shift and further increased the chance of rain through this window
of time. The second should move over the area late Sunday through
late Monday, boosting showers mainly across the eastern end of
the state. Again, PoPs have been further increased. Finally,
another area may reach us next Thursday, but at this time range
confidence is low. Models currently indicate the focus of this one
would be on the eastern end.

Trade winds will remain moderate to breezy through the coming
week, with the a slight increase possible Tuesday evening. A
slight weakening may develop next Thursday, but as mentioned in
the previous paragraph, at seven days out, confidence in that
level of detail is low.

Finally, both the latest GFS and ECMWF indicate that the upper
level trough extending from southern CA over to us may join with
energy moving in from the northwest and strengthen toward the
middle of next week. It is unclear at this time whether it will
develop into a closed low or a stronger trough. Either way, it may
draw tropical moisture northward toward the state and present a
heavy rain threat. Details should become clearer in a few days.


&&

.AVIATION...

Gusty trade winds have been observed at several terminals today
(PHNL, PHOG, PHMK, PHJR). Gusts should ease somewhat this evening
with the typical diurnal decrease, then increase again Friday.
Isolated MVFR conditions are possible in passing showers
overnight. Otherwise, VFR conditions will prevail.

AIRMET Tango is in effect for moderate low-level turbulence
downwind of island terrain.


&&

.MARINE...

Surface high pressure far north of the islands will build as it
shifts northeast of Hawaii through Saturday. As a result, trade
winds will gradually increase to fresh to locally strong levels
over the next couple of days. A Small Craft Advisory (SCA) is in
effect for the typically windy waters around Big Island and Maui
through Saturday and may need to be expanded in area as the high
builds to the north. Elevated trade winds will persist into early
next week.

The current small bump in the northwest swell will fade tonight
before a moderate north-northwest swell arrives Friday. Surf along
north and west-facing shores should top out near or slightly
above seasonal average during the peak of the swell Friday
afternoon and Saturday, then slowly decline late Saturday and
Sunday as the dropping swell shifts more northerly and a smaller
overlapping northwest swell arrives. Both swells will fade early
next week.

A new long-periond south swell will gradually build this evening
and may push surf along south-facing shores back above seasonal
average into Friday. This swell will slowly decline Saturday
through early next week.

Surf along east-facing shores will gradually increase tonight
into Friday as trade winds strengthen over the region. Expect some
wrap from the moderate north-northwest swell Friday afternoon
into Saturday. This swell along with developing rough trade wind
swell will produce east shore surf above seasonal average Saturday
through early next week.
&&

.FIRE WEATHER...
Issued at 259 PM HST Thu Oct 15 2026

Surface high pressure north of the islands will produce moderate
to breezy trade winds for the next few days. Minimum relative
humidity levels will for most areas remain out of critical fire
threshold ranges. The stronger trade winds will mainly impact
higher elevation areas with even higher minimum humidity levels.
Subsidence temperature inversion heights today near Maui and the
Big Island should range from 9,000 to 11,000 foot through Friday.


&&

.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...Parker
AVIATION...PECHACEK
MARINE...Farris