Drought in Hawaii, September 22 to 30, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
845 PM HST Mon Sep 21 2020

.SYNOPSIS...
Showers will remain focused over mainly windward areas through
Tuesday. Leeward areas will be mostly dry except for afternoon
and evening showers over the lee slopes of the Big Island. A cloud
area moving west across the islands Wednesday and Thursday may
bring an increase in showers. Moderate easterly trade winds will
strengthen slightly as a high far northwest of the area shifts
southeast. Winds are expected to diminish again over the weekend.

&&

.DISCUSSION...
A surface ridge north of the area is producing moderate easterly
trade winds across the islands. The atmosphere is rather dry and
stable thanks to a ridge aloft over the are. The trade winds will
push a few showers over windward areas, mainly during the night
and early morning hours. Leeward areas will remain mostly dry
except for afternoon showers over the lee slopes of the Big
Island. The high clouds that have been dimming the sun will be
clearing away overnight.

Satellite loops show an area of showery low clouds about 400 miles
east of the islands moving west in the trade-wind flow. This
cloud area is the remnant of Tropical Storm Karina. As the cloud
area moves west across the islands Wednesday and Thursday, our
weather will turn wetter, especially over the Big Island. The
ridge aloft will remain over the islands limiting the amount of
rainfall. Drier weather will return as the cloud area moves away
to the west Thursday night.

The trade winds will strengthen a bit over the next couple of days
as a surface high far northwest of the islands moves southeast.
Winds will weaken again late in the week as the high moves off to
the east and a front approaches from the northwest.

Autumn will arrive at 3:31 am HST Tuesday morning.

&&

.AVIATION...
Light to locally moderate trade wind flow will persist through
twenty-four hours and beyond. The air mass will remain mostly dry
and mostly stable. Low topped clouds and showers will favor
windward slopes and coasts. Light afternoon sea breezes along
Leeward coasts will give way to weak land breezes after sunset.
Gradual nighttime clearing will allow skies to become mostly clear
by morning across most leeward coasts.

VFR conditions will prevail all areas. Brief MVFR conditions can
be expected over windward slopes and summits as moisture embedded
in the trade wind flow interacts with island terrain. No AIRMETs
are in effect or anticipated at this time.

&&

.MARINE...
Moderate to fresh trades will remain across the coastal waters for
much of the week. An ASCAT pass earlier in the day indicated some
SCA level winds in the Alenuihaha Channel. Subsequent high
resolution models runs have indicated that winds won't drop much,
if all, over the next day or two. As such, have issued a Small
Craft Advisory for the typical windier areas near Maui County and
the Big Island. High pressure is expected to build north of the
state Wednesday through Friday, so expect the winds to be stronger
during that time period. Some weakening is expected this weekend.
Surf along east facing shores will increase some later this week
with the winds increasing, but is expected to peak below advisory
levels.

A long period north northwest swell will build late Tuesday
night, peak Wednesday night/Thursday at around 6 feet and 15
seconds, followed by gradual lowering through Friday. Expect
surf to peak just below advisory levels for the north shores.

A small south southwest swell is due in tonight, leading to near
summer time average of 3 to 5 feet surf through midweek. Another
small south southwest swell is possible Friday into Saturday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
.Small Craft Advisory until 6 AM Thursday for Maalaea Bay, the
Pailolo and Alenuihaha Channels and waters south of the Big
Island.

&&

DISCUSSION...Donaldson
AVIATION...Bedal
MARINE...M Ballard