Heavy Rain in Hawaii, June 19, 2021

Area Forecast Discussion
National Weather Service Honolulu HI
400 PM HST Sat Jun 19 2021

.SYNOPSIS...
Stable conditions will return tonight and we should see light to
moderate trades through at least the first half of the new week.
The weaker trade wind flow should allow sea breezes to develop
each afternoon across select leeward areas, followed by land
breezes at night.

&&

.DISCUSSION...
The upper level low north of the state continues to slowly drift
away from the area this afternoon. Brief heavy showers were seen
earlier this afternoon across select leeward areas especially over
Oahu and the Big Island. A quick 0.25 inch to 0.5 inch of
precipitation was recorded across several rainfall stations. As we
head into the evening hours, we should see the showers gradually
taper off, but a few scattered showers will continue to ride in
with the light to moderate trade winds. As the upper level low
lifts away from the area, we should see a ridge build in aloft and
stable conditions are expected to persist through much of the new
week.

The forecast models keep light to moderate trade winds in the
forecast through the middle of next week. The relatively weak
trade wind regime may allow alternating local afternoon sea
breezes and nighttime land breezes to develop over each of the
individual islands next week. The sea breezes could result in some
clouds forming over leeward and interior sections of the islands
each afternoon. However, the stable and dry atmospheric conditions
will likely limit afternoon shower coverage. The land breezes,
which will initially become established each evening, will tend to
clear skies over most of the islands at night.

&&

.AVIATION...
No AIRMETs are in effect and none are expected today. VFR
conditions will prevail.

Afternoon heating produced clouds and some showers over west
sections of the main Hawaiian islands. A low aloft north of the
area is creating some instability. That contributed to the
formation of locally heavy showers this afternoon. As the sun
sinks and daytime heating abates, the showers will subside. A high
far northeast of the main Hawaiian Islands will maintain moderate
east winds over the area. The easterly flow will carry scattered
clouds and isolated showers over east sections of the islands
overnight.

&&

.MARINE...
A surface high northeast of the islands will maintain a trade wind
background flow over the islands, however the pressure gradient
remains on the weaker side. As a result, winds are currently well
below Small Craft Advisory (SCA) and are expected to remain below
SCA through the upcoming week. The high is expected to weaken
during the next week as several front pass north of the islands.
This will cause winds around the islands to become even lighter
at times.

A long period south swell is expected to arrive today, which will
boost surf heights, with surf approaching advisory levels
tonight or Sunday. Currently the near shore buoys are reporting 14
second energy, so still awaiting the arrival of the longer period
energy to evaluate the timing of the this event. This event is
expected to peak Sunday and then then gradually decline through
the middle of the week. Otherwise surf is expected to remain small
along remaining shorelines.

&&

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

&&

DISCUSSION...Kino
AVIATION...Donaldson
MARINE...M Ballard