Drought in Hawaii, July 1 to 31, 2021

Area Forecast Discussion
National Weather Service Honolulu HI
834 PM HST Wed Jun 30 2021

.SYNOPSIS...
A surface high far northeast of the area will build southwest.
Breezy easterly trade winds will persist through the Independence
Day holiday weekend. Ridging aloft will keep the atmosphere dry
and stable. The trade winds will carry clouds and some showers
over windward areas, during mainly night and morning hours.
Leeward areas of the smaller islands will be mostly dry. Clouds
and showers will affect the Kona slopes of the Big Island during
the afternoons and evenings.

&&

.DISCUSSION...
The global models continue to agree that a high far northeast of
the main Hawaiian Islands will build southwest over the next
several days. Breezy trade winds will persist. Ridging aloft will
produce subsiding air over the islands with a rather strong and
low temperature inversion. The inversion will cap low level clouds
and keep rainfall very light over most areas. The trade winds will
push clouds and some showers over windward areas. These showers
will be most active during the nights and early mornings. Leeward
areas of the smaller islands will remain very dry. The trade winds
will be blocked by the high terrain on the Big Island from
reaching the Kona district, so afternoon clouds and showers will
develop over the Kona slopes and persist into the evening hours.

&&

AVIATION...
As high pressure strengthens from the northeast, trade winds will
be on the increase across the area. A limited amount of showery
low clouds, with accompanying MVFR conditions, will mainly affect
windward and mauka sections across the island chain.

No AIRMETs are currently in effect, but AIRMET Tango may need to be
issued later tonight or Thursday as trade winds become more
robust and the potential for low level turbulence S thru W of the
mountain ranges increases.

&&

.MARINE...
Fresh to strong easterly trade winds will continue through the
holiday weekend as high pressure builds to the north and the
gradient remains tight over the region. The Small Craft Advisory
in effect for the windier waters around the Big Island and Maui
may need to be expanded to other areas later in the week and
through the weekend. Seas will become rough over the channels
this weekend, likely nearing the 10 ft advisory threshold. No
significant changes are anticipated early next week.

A solid south-southwest swell from recent activity across the
southern Pacific filled in today and topped out around the
advisory level (8 ft faces). Latest nearshore PacIOOS buoy
readings reflect this source this evening holding within the 15-16
sec bands. Expect this swell to hold Thursday before tailing off
Friday into the holiday weekend.

The active trend will continue along south facing shores early
next week as the largest swell of the season arrives. The archived
surface analysis and satellite retrievals showed a large area of
storm-force winds with seas estimated just above 40 ft within
Hawaii's swell window southeast of New Zealand as a 963 mb low
passed through a couple of days ago. WAVEWATCH III has this
source peaking at the Pago Pago PacIOOS buoy Friday night, which
should correspond to a peak locally late Monday through Tuesday
well above advisory levels. Forerunners should begin to move
through Sunday night, then build all day Monday. This should be a
long-lived event that holds through midweek before easing late
next week.

Surf along exposed north and west facing shores will trend up
Friday through Saturday as a small, northwest swell arrives from a
gale centered near the Date Line over the Aleutian Islands
(Typhoon Champi recurved and became absorbed into the Aleutian
low). Otherwise, summertime conditions are anticipated.

Surf along east facing shores will slowly trend up and become
rough over the holiday weekend as the trades strengthen locally
and upstream.

&&

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

&&

DISCUSSION...Donaldson
AVIATION...Kinel
MARINE...Gibbs