Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 05/17/2026 11:31:00 PM UTC

                        
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FXHW60 PHFO 171331
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
331 AM HST Sun May 17 2026

.SYNOPSIS...
A slightly unstable and somewhat wet trade wind flow will continue
into Monday. An increasingly stable, moderate to breezy trade
wind flow will develop Tuesday and Wednesday and will persist into
next weekend.

&&

.DISCUSSION...
Scattered heavy showers over windward areas diminished overnight
as the upper level low that lingered over the area during the past
couple of days lifted away to the northeast. A handful of
windward stations picked up 1 to 2 inches of rainfall, mainly
before midnight. Little rainfall managed to make it leeward areas
since the local pressure gradient and resulting trade winds
remained somewhat weak due to the effects of the upper low.

Moderate easterly winds and a somewhat wet pattern of mainly
windward and mauka showers is expected over the next couple of
days. The GFS and ECMWF show moisture remaining slightly elevated
and dew points hanging on in the upper 60s to lower 70s, allowing
the humid trade wind flow to continue to produce showers over
windward areas. Broad troughing aloft will maintain some
instability, which could still trigger a briefly heavy shower,
mainly over the heated leeward slopes of the Big Island and Maui
during the afternoon hours.

Increased stability and stronger trade winds are due late Tuesday
or Wednesday. Expect a typical pattern of mainly windward rainfall
and mostly dry conditions leeward into next weekend.

&&

.AVIATION...
Flight weather conditions will improve today as the upper level
disturbance continues to drift eastward away from the Hawaiian
Islands. Brief showers linger in the forecast mainly over
windward and mountain areas of each island.

AIRMET Sierra remains in effect for mountain obscuration for the
east section of Maui.

&&

.MARINE...
Moderate to locally fresh easterly trades have returned. An upper
level-low that plagued the state has moved off to the northeast,
increasing stability and decreasing showers.

A small, medium-period north northwest (320-330 degree) swell will
continue to decline through tonight, with surf along north-
facing shores following suit. A medium-period north-northwest
reinforcement may provide another small bump in surf along north-
facing shores by early Monday morning, followed by another small
reinforcing swell on Tuesday.

Surf along west-facing shores will remain nearly steady through
the rest of the weekend as the northwest swell influence gradually
declines, but a new, long-period south southwest swell fills in.

A mix of small, medium- to long-period south swells will maintain
small surf along south-facing shores for the next several days.
The long-period south-southwest swell described above will
increase surf along south-facing shores through today. Additional
small, medium- to long-period south swell reinforcements will
arrive through midweek.

Moderate to fresh trades will maintain rough and choppy surf
along east-facing shores for the next several days.

Tides will peak around 2.5 to 3.0 ft MLLW today. Minor overwash
of low lying coastal areas will be possible during times of high
tide.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Wroe
AVIATION...Bohlin
MARINE...Walsh