Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 10/16/2026 05:22:00 AM UTC

                        
381
FXHW60 PHFO 151922
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
922 AM 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 Sunday night into Tuesday morning.

&&

.SHORT TERM UPDATE...Isolated to scattered trade showers continue
this morning, mainly across windward and mauka areas, but a few
are bleeding over to leeward areas. These showers should diminish
in coverage and intensity in most areas heading into the
afternoon. The exception will be on the Big Island, where windward
showers will continue and Kona showers will develop this afternoon
as a weak easterly wave moves through. The forecast is on track
and no update is needed this morning.

&&

.PREV DISCUSSION...
Issued at 331 AM HST Thu Oct 15 2026
The satellite imagery this morning shows a lingering band of
unstable showers riding into the windward mountain slopes of each
island on the trade winds. Periods of windward and mountain
showers should be expected for the typical areas, more isolated
showers are possible for drier leeward locations. Increased
rainfall coverage in the morning forecast to account for the
additional activity. These enhanced trade wind shower trends will
diminish in coverage a few hours after sunrise due to the typical
diurnal day time stability trends. Farther to the east, the
satellite imagery verifies three short waves moving towards the
islands within the easterly trade winds. These easterly waves will
bring pulses of showers to all islands as they march across the
island chain from Friday into early next week.

In the big picture, we continue to track a high pressure system
currently located far northwest of the Hawaiian Islands drifting
eastward over the next few days. This migratory high will increase
easterly trade winds into the moderate to breezy range lasting
into next week Tuesday.

Periods of wet weather remain in the weather forecast for this
weekend as the three low level easterly waves will ride into the
islands on the strengthening trade winds. Three pulses of higher
shower coverage will favor Friday night, then late Saturday, and
the last one unfolding from Sunday through Monday. The last of
these easterly short wave troughs might be the strongest of the
three with enhanced showers extending over the typically drier
leeward areas at times. Forecasting rainfall amounts with these
waves is always challenging due to variations in arrival timing
and their intensity relative to each island.

A larger degree of uncertainty remains in the long range forecast
from next week Wednesday onward. Both the American (GFS) and
European (ECMWF) global forecast models continue to show diverging
solutions for a passing middle latitude trough as the trough digs
in and potentially approaches the islands from the northwest. The
GFS model solution deepens this trough into a large cut off low
north of Kauai and secondary upper low deepens northeast of the
Big Island from Thursday into Saturday. The GFS shows us a wetter
solution for sure as upper level cold core temperatures and
additional divergence aloft will lift inversion heights and
produce a surface trough likely producing southeasterly to
southerly winds near the islands at some point. However, the ECMWF
model presents a much more stable solution with two weaker upper
lows north of the state. This european model solution will produce
more stable conditions, as compared to the GFS model, with a
typical trade wind shower pattern setup.

We will continue to closely monitor this long range forecast time
period for potential island by island weather impacts as the model
solutions begin to converge and the weather forecast becomes
clearer over the next several days. Stay tuned.

&&

.AVIATION...
Trade winds will become more gusty today and isolated showers
across windward areas of the Big Island could create isolated MVFR
condition and possibly into Maui. Otherwise VFR conditions will
prevail over the rest of the terminals.

No AIRMETs are in effect, however as winds increase, AIRMET Tango
may be needed for mechanical turbulence to the lee of the
mountains.

&&

.MARINE...
Surface high pressure far northwest of the islands will move
closer today, then build as it shifts north and then northeast of
Hawaii on Friday. 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 beginning at 6 am this morning.
A stronger surface high will arrive far north of the islands late
Saturday and Sunday, likely increasing trade winds further, which
may necessitate an expansion of the SCA to additional waters.
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 and
continues through the weekend. Surf along north and west-facing
shores should top out around seasonal average or slightly higher
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 builds today and may push surf
along south-facing shores back above seasonal average into Friday.
The swell will slowly decline Saturday through early next week.

Surf along east-facing shores will begin to increase this
afternoon into tonight as trade winds strengthen over the region.
Expect some wrap from the moderate north-northwest swell tomorrow
afternoon into Saturday. Rough trade wind swell will produce east
shore surf above seasonal average Saturday through early next
week.

&&

.FIRE WEATHER...
Issued at 331 AM HST Thu Oct 15 2026
A high pressure system far north of the islands drifting eastward,
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 will drop into the 6,000 to 7,000
foot elevation range this afternoon.

&&

.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.


&&

$$

SHORT TERM UPDATE...Parker
DISCUSSION...Bohlin
AVIATION...PECHACEK
MARINE...Farris