Drought in Hawaii, June 1 to 30, 2021

Area Forecast Discussion
National Weather Service Honolulu HI
825 PM HST Mon May 31 2021

.SYNOPSIS...
Trade winds will return from east to west across the state
tonight and Tuesday, reaching moderate levels by Wednesday and
persisting through early next week. Rather dry conditions will
prevail through Wednesday night, with showers mainly confined to
windward and mauka areas. The remnants of an old front will likely
bring a notable increase in showers to Kauai and possibly Oahu
Thursday through Friday. A more typical trade wind pattern is then
expected Saturday through early next week, with showers favoring
windward and mauka areas, mainly at night and during the early
morning hours.

&&

.DISCUSSION...
Currently at the surface, a weak front is nearly stationary
around 250 miles northwest of Kauai. Meanwhile, a 1027 mb high is
centered 1600 miles northeast of Honolulu, with a ridge axis
extending southwestward through the Garden Isle. The resulting
gradient is producing light and variable winds over the western
islands, with light to moderate trades over the eastern end of the
state. Infrared satellite imagery shows clear to partly cloudy
conditions in most areas. Radar imagery shows a few lingering
daytime heating driven showers, but most areas remain rain free.
Main short term concern revolves around the returning trades.

The front northwest of the state will gradually dissipate during
the next couple days, allowing for trade winds to return from
east to west across the island chain and strengthen to moderate
speeds statewide by mid week. High pressure will then strengthen
as it lifts northeastward Thursday through early next week,
although the pressure gradient will change little during this
time. As a result, moderate trade winds should prevail from
Wednesday through next Monday, with only minor fluctuations in
strength from day to day.

As for the remaining weather details, dry and stable conditions
will persist through Tuesday, with a few showers possible near
the coast tonight and over the island interiors Tuesday afternoon.
We should see a transition over to a windward and mauka focused
shower pattern Tuesday night through Wednesday night, although it
will be much drier than normal with the stable conditions in
place. Both the GFS and ECMWF show a band of higher precipitable
water values associated with the remnants of an old front sinking
southward and into the western islands Thursday and Thursday
night, which will likely bring a notable increase in trade wind
showers to Kauai and possibly to Oahu, while Maui County and the
Big Island remain in a dry trade wind regime. The remnants of the
old front may linger over Kauai into the day Friday, before
lifting northwest of the islands, putting the entire island chain
in a dry trade wind pattern Friday night. A more typical trade
wind pattern should settle in Saturday through early next week,
with showers focused mainly over windward and mauka areas, and a
stray shower occasionally reaching leeward communities.

&&

.AVIATION...
Weak background flow across the state will allow light land
breezes to predominate overnight. Trade winds will rebuild on
Tuesday.

Land breezes will promote clearing overnight, especially along
leeward slopes. On Tuesday, light trade winds will steer clouds
and a few showers towards windward slopes and coasts of all
islands. Sea breezes will still prevail across leeward portions
of the Big Island on Tuesday where they will focus afternoon
cumulus buildups along south and west facing slopes.

No AIRMETs are currently in effect or anticipated at this time.

&&

.MARINE...
A front northwest of the islands is pressing a ridge axis down
over the state. This has created the current light, variable
breezes over the western islands and gentle to moderate east-
southeast winds across the eastern side of the state. Trade winds
will return from east to west across the island chain Tuesday. Mid
week moderate trades will strengthen to more areawide fresh to
locally strong speeds through the windier channels and bays late
this week.

The current small northwest swell will trend up through Tuesday
and peak surf along north and west facing shores. This swell will
trend down to near flat by Friday. A series of small southerly
swells will maintain slightly below normal surf along southern
shorelines through Tuesday. South shore surf could trend up
slightly from Wednesday into the weekend with the arrival of a
couple of overlapping slightly larger, higher energy south and
southwest swells. East facing shore surf will remain small through
Tuesday. Mid to late week strengthening trades over and upstream
of the islands will bump up shorter period wind waves and hold an
early June chop along eastern coasts.

&&

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

&&

DISCUSSION...Jelsema
AVIATION...Bedal
MARINE...Blood