Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 06/21/2026 05:18:00 AM UTC

                        
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FXHW60 PHFO 201918
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
918 AM HST Sat Jun 20 2026

.SYNOPSIS...
Light to moderate east-southeasterly winds will persist today,
then take on an east northeasterly component by Sunday. Despite
the slight variation in wind direction, the light to moderate
background flow will bring a combination of mainly isolated
windward and mauka showers along with sea breeze induced leeward
and interior showers. Early to mid- next week, trade winds will
strengthen to moderate to breezy levels, bringing a return to more
consistent windward showers.

&&

.SHORT TERM UPDATE...
Limited clouds and a few showers can be seen moving into windward
and mauka areas on the light to moderate east-southeast flow this
morning. With abundant sunshine quickly warming the land, sea
breezes have already started to develop along the most protected
leeward areas. As the day progresses, these sea breezes will drive
localized cloud buildup and spotty showers across interior and
leeward sections, while windward slopes continue to see only
isolated activity. The current forecast remains on track, so no
changes were made with this mid-morning update.

&&

.PREV DISCUSSION...
Issued at 357 AM HST Sat Jun 20 2026

Mainly dry conditions prevailed overnight across the state with
very little low cloud cover and isolated showers. Areas along the
windward slopes saw most shower coverage, though only a few
hundredths of an inch of accumulation were reported. A typical
lower level moisture profile can be noted on the 12Z RAOB
sounding at Hilo and Lihue with a capping boundary layer
temperature inversion height of around 7,000 feet. Dry and stable
air dominated in the mid and upper levels. Zooming out, a
stationary front was analyzed to the northwest of the state and a
1029 mb surface high resided well to the northeast. These features
should help maintain light to moderate east southeast flow today,
backing to east northeast by Sunday. Despite the slight variation
in wind direction, the light to moderate background flow will
bring a combination of mainly isolated windward and mauka showers
along with sea breeze induced leeward and interior showers. It may
feel humid once again today with dewpoints hovering in the lower
70s. However, expect some relief for Sunday and beyond as we
transition into a more traditional east northeast trade wind
pattern and dewpoints gradually fall back into the mid to upper
60s.

Monday through Friday, the aforementioned frontal system northwest
of the islands weakens into a trough, moves west, and is replaced
by an large area of surface high pressure. Tightening local
surface pressure gradients across the state will lead to moderate
to locally breezy trade winds. In addition, both the GFS and
ECMWF models deepen a longwave trough north of the islands, pinch
off an upper low, and retrograde it to the west southwest. There
still remains some variance between the global models on where
this upper level low tracks, but as it nears the islands by
midweek, it may enhance trade wind showers as batches of moisture
roll through.

&&

.AVIATION...
Issued at 357 AM HST Sat Jun 20 2026

Stable weather conditions will continue through the weekend as
strong subsidence aloft limits vertical cloud development over
the islands. Light to moderate trade winds will persist as a
diminishing stationary front far north of the islands keeps the
high pressure ridge in a weakened state. Trade winds strengthen by
Monday. No AIRMETs in effect.

&&

.MARINE...
Issued at 357 AM HST Sat Jun 20 2026

Light to moderate trades will hold for the next couple of days as
a weak surface ridge remains northeast of the area and a front
passes to the north. Trade winds will begin to increase Monday
and trend upward through next week as the front dissipates and the
ridge strengthens north of island chain.

A small, medium-period south swell will continue to fade while a new
long-period south swell builds through the day. Surf along south and
west-facing shores should trend upward by the afternoon and peak
overnight before diminishing on Sunday. Multiple other small, medium
to long period south and southeast swells also arrive through the
middle of next week, which will maintain surf heights near seasonal
averages.

Tiny surf will prevail along north-facing shores through most of
the coming week as limited short-period energy reaches the islands
from the north and northwest. Trade winds remain lighter than normal
through the weekend, keeping surf along east-facing shores below
average. East shore surf will begin to trend up early next week as
trade winds increase across and upstream of the region.

&&

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

&&

$$

DISCUSSION...Thomas
AVIATION...Bohlin
MARINE...Quesada