Drought in Hawaii, June 22 to 30, 2021

Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
857 PM HST Mon Jun 21 2021

.SYNOPSIS...
A ridge of high pressure currently 530 miles north of Kauai will
move south to about 220 miles north of Kauai Thursday. The ridge
will remain there through Friday night before moving north. This
action translate to trade winds continuing over the area to
Thursday, then give way to slight southeast winds over the
smaller islands on Friday and part of Saturday. Trade winds
strengthens over the area Saturday night through Sunday. Look for
trade showers to pickup overnight and mornings favoring the
windward and mountain areas.

&&

.DISCUSSION...
A 1029 mb surface high is centered 1350 miles far north-
northeast of the islands this evening. A ridge extends southwestward
to about 530 miles north of Kauai. The high will linger where it
is now to until Thursday before racing north becoming stationary
off the Oregon coast on Friday. The surface ridge will be moving
south in the mean time, becoming nearly stationary 220 north of
Kauai Thursday. This action will cause the trade winds to veer a
little east-southeast over the smaller islands. With this wind
flow, islands downwind of Maui and Big Island will be blocked,
causing a mix of light easterly and a daytime sea breeze and
nighttime land breeze. This hybrid pattern will last a day, may
be two, through Saturday, with strengthening trades returning
Saturday night.

Corrected
Satellite imagery and weather radar is not showing much low clouds
and showers over and upwind of the islands. There is a layer of
mainly thin high cirrus clouds covering the eastern two third of
the island chain. The Kona coast has been the wettest with some
good afternoon and evening showers, with Kapapala Ranch receiving
4 tenths of an inch this afternoon. Most of these showers have
ended, but do expect a shower or two to linger near its coast for
the rest of the night.

The GFS is indicating a mid level ridge over the islands that
will be strengthening through Tuesday. With this said, this trade
wind pattern will be rather dry during the next 24 hours. If there
are any showers tonight and Tuesday, they will be light and brief,
and confined to the windward and mauka areas.

The GFS and ECMWF are both indicating a little influx of low level
moisture returning Tuesday night to especially windward Maui and
windward Big Island. An upper level impulse will be dropping down
on the islands from the north Wednesday, eroding the mid level
ridge and allowing for an uptick in trade showers Wednesday night
through Thursday.

As noted above, the trade winds turn east-southeast over the
smaller islands Thursday night into Friday. And with the lingering
impulse above, we may see more showers Friday afternoon. Further
details will be forthcoming.

&&

.AVIATION...
Light to locally moderate trade wind flow will persist for the
next few days. Scattered low clouds and showers will favor east
and northeast facing slopes and coasts, especially in the late
night and early morning hours. Isolated MVFR conditions are to be
expected in passing showers, otherwise VFR conditions will
prevail.

The lighter background flow will allow localized sea breezes to
develop along leeward coasts in the afternoon and early evenings,
promoting areas of inland cloudiness.

No AIRMETs are currently in effect or anticipated at this time.
However, model guidance suggests an area of moderate upper-level
turbulence developing over the far western portion of the forecast
area Tuesday morning. Will monitor for potential AIRMET Tango.

&&

.MARINE...
A ridge northwest of the area will moderate to locally fresh
easterly trade winds across the coastal waters for the next few
days. The winds will strengthen over the weekend and may reach
Small Craft Advisory levels around Maui and the Big Island.

The current south swell will subside through Tuesday. Small to
moderate south swells are expected through the weekend. Small
northwest swells will continue into the weekend. The weaker than
normal trade winds will limit surf along east facing shores but
stronger winds off the California coast will produce a small
northeast swell.

&&

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

&&

H Lau/Bedal/Donaldson