Drought in Hawaii, May 1 to 10, 2022

Area Forecast Discussion
National Weather Service Honolulu HI
839 PM HST Sat Apr 30 2022

.SYNOPSIS...
Strong trade winds will decrease slightly by Tuesday but remain
breezy through the rest of the week. An upper trough approaching
from the west will destabilize our weather Sunday afternoon
through the rest of the forecast period. Showers will increase
Sunday into Sunday night, with wet and breezy trade wind weather
expected through the first half of the new week. Locally heavy
rainfall is possible over windward areas Sunday evening through
Monday.

&&

.DISCUSSION...
Thanks to an upper trough west of the main Hawaiian Islands, a
shield of high clouds blocks the view of lower clouds across the
islands this evening. Marking the eastern flank of the upper
trough, these clouds will likely stick around into next week as
the upper trough drifts eastward. Radar shows scattered showers
embedded within strong trade wind flow, favoring windward areas.

An unstable pattern will develop as the approaching upper trough
pinches into an upper low just north of the chain, then lingers
nearby through much of the forecast period. Models show an area
of enhanced low level moisture will be near the Big Island Sunday
morning. This moisture will spread westward to the smaller
islands by Sunday night. The combination of increased moisture and
increased instability will enhance showers over windward areas
with the potential for showers to anchor along terrain. Leeward
areas should see scattered showers as well from time to time on
Sunday.

The Big Island will have the greatest chance for heavy rainfall
and isolated thunderstorms Sunday afternoon through Monday, with
this chance tapering off farther to the west. East Maui may also
be affected. This setup may continue through the middle of the
week as the upper low lingers in the area. The threat for heavy
rain and isolated thunderstorms will depend on the location and
strength of the forecast upper low. Models show the upper low
lingering nearby through Thursday. There are still some
uncertainties regarding the strength and position of the low but,
with unstable conditions expected, we should see showery
conditions this week, especially across windward areas.

&&

.AVIATION...
A large area of high pressure anchored north of the state will
maintain moderate to locally strong trade winds across the islands
through the weekend. This pattern will continue to force a
majority of clouds and showers along east/northeast facing slopes,
coasts, and within channels between islands through the TAF period.
Weaker gradient flow lingering within sheltered leeward areas,
will allow for sea breeze clouds and possible isolated showers
Sunday afternoon across interior sections of the the Big Island.

AIRMET Tango for low-level mechanical turbulence immediately
south through west of higher terrain, remains in effect for all
islands this weekend. Also, a period of light ice could
potentially develop in a shallow layer between FL180/280 through
Sunday morning, mainly stretching from Maui to the Big island, as
mid and upper lvl moisture continues to lift up across the
islands.

&&

.MARINE...
High pressure northeast of the area is producing breezy to
locally windy trade winds across the area. A Small Craft Advisory
(SCA) is currently posted for the typically windy waters around
Maui County and the Big Island. Winds are expected to be a bit
stronger Sunday and Sunday night so the SCA will be expanded to
included all Hawaiian Coastal Waters beginning Sunday morning.

The current small, short period northwest swell will linger
through Sunday. A larger and longer period northwest swell is
expected to arrive Monday. The swell will then get a
reinforcement late Tuesday into Wednesday with surf heights
possibly reaching low end advisory levels. This swell will then
lower gradually through the remainder of the week.

Small, mainly background south swells are expected through Sunday.
A slightly larger and long period south swell is then expected to
arrive Sunday night and Monday, then linger on into Tuesday. An
even larger south swell is then expected to arrive by Wednesday.
Data from the Aunuu Buoy in American Samoa indicates that this
well is running higher than model guidance. This swell may be
large enough for surf heights to reach low end advisory levels
during its peak late Wednesday and Thursday. This swell will then
lower gradually through the remainder of the week.

Trade winds over and upwind of the state will continue to produce
short period choppy surf along east facing shores through the
weekend and on through all of next week. Surf heights are expected
to remain below advisory levels.

&&

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

Small Craft Advisory from 6 AM Sunday to 6 AM HST Monday for
Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-
Kaiwi Channel-Maui County Windward Waters-Maui County Leeward
Waters-Big Island Windward Waters.

&&

DISCUSSION...Powell
AVIATION...SWR
MARINE...Foster