Drought in Hawaii, April 19 to 30, 2022

Area Forecast Discussion
National Weather Service Honolulu HI
831 PM HST Mon Apr 18 2022

.SYNOPSIS...
A high pressure ridge north of the Hawaiian Islands will keep
moderate to breezy trade winds in the forecast through the
weekend. Expect brief periods of showers mainly affecting windward
and mountain areas favoring the overnight to early morning hours
through the week. An upper level trough and jet stream will keep
high clouds over the region through the week.

&&

.DISCUSSION...
The evening satellite imagery over the region shows an upper level
trough over the state with a subtropical jet stream just south of
the trough axis spreading high cirrus clouds over Maui and the Big
Island. Low level cloud bands upstream of the islands associated
with a dissipated frontal boundary will continue to drift through
the islands with brief periods of showers forecast through the
overnight to early morning time period. Upper level high cirrus
clouds are expected to drift across the state through the week,
enhancing sunrise and sunset colors.

In the big picture, the subtropical ridge will remain anchored in
place north of the island chain. This ridge will keep moderate to
breezy trade winds in the forecast through the upcoming weekend. A
1030 mb high pressure center within this ridge is currently
located northwest of the islands producing northeasterly trades.
As this high center slowly drifts eastward from Tuesday to
Wednesday the trade wind directions will veer from a northeast to
east direction by the middle of the week. The high center will
continue to drift into the East Pacific basin on Friday and
Saturday with a slight east to southeasterly shift in wind
directions. An approaching cold front will stall out northwest of
the islands on Friday with little impacts to our island weather.

The weather pattern in the short term through the week remains
fairly typical for this time of year. The breezy northeasterly
trade winds will keep brief windward and mountain showers in the
forecast with pleasant weather for most locations each day. Some
isolated stronger showers may reach leeward sections mainly in
the overnight hours. Longer range forecast guidance continues to
show some added instability from an upper level low setting up
just west of the state. This disturbance may increase shower
trends, especially over the western islands, on Thursday and
Friday. The weather forecast this weekend has improved with an
upper level ridge aloft settling in over the region along with
more east-southeast winds suppressing shower activity for most
islands. Eastern slopes of the Big Island will continue to see
passing showers.

&&

.AVIATION...
Locally breezy trades will focus clouds and showers over windward
and mauka zones through the period. This will particularly the
case for Oahu where trades will push a loosely organized band of
showers onshore through much of the night. As these showers
increase in coverage during the next few hours, AIRMET Sierra for
mountain obscuration may be needed for Windward Oahu. For the
other islands, any MVFR is expected to be brief.

AIRMET Tango remains in effect for both low level lee turbulence
as well as moderate upper turb FL280/420.

&&

.MARINE...
Moderate to strong trade winds will continue through the weekend
and into early next week, with only minor variations in strength.
A Small Craft Advisory (SCA) remains in effect for the waters west
of Molokai through 6 PM Tuesday, and for the typically windy
waters around Maui and the Big Island through 6 PM Wednesday. The
SCA will likely continue through much of the week for the windier
areas around Maui and the Big Island.

Surf along north and west facing shores will remain small through
Tuesday, then trend up Tuesday night through midweek as a new
long-period, northwest swell arrives and builds down the island
chain. Surf associated with this swell will peak through the day
Wednesday (below advisory levels), then slowly lower through the
second half of the week as the swell direction shifts out of a
more northerly direction. Another north-northwest swell arriving
over the weekend could push north shore surf up close to advisory
levels late Saturday into Sunday.

Surf along south facing shores will steadily lower tonight through
midweek as the current south swell eases. A new south swell is
forecast to arrive Friday night, building south shore surf to
above the summertime average through the weekend into early next
week.

Surf along east facing shores will remain rough and choppy due to
strong trade winds. The surf will remain below seasonal levels
however, due to the lack of a sizable fetch upstream of the
island chain.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel.

&&

DISCUSSION...Bohlin
AVIATION...JVC
MARINE...Jelsema