Drought in Hawaii, September 1 to 30, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
824 PM HST Mon Aug 31 2020

.SYNOPSIS...
A high pressure ridge north of the islands will decrease in
strength over the next two days as a cold front moves through the
northeast Pacific, causing a weakening trend in local area trade
winds. Moderate to locally breezy trade winds will continue
tomorrow becoming light to moderate by Wednesday. Fairly dry
weather trends will continue with isolated to scattered shower
coverage mainly along windward and mountain slopes in the
overnight to early morning hours. These fair weather conditions
will last into the upcoming weekend.

&&

.DISCUSSION...
The large scale weather picture remains unchanged as the high
pressure ridge north of the islands decreases in strength in
response to a cold front moving through the northeast Pacific.
Local area pressure gradients will weaken causing trade wind
speeds to slowly decrease over the next 48 hours. Expect moderate
to locally breezy conditions on Tuesday, followed by light to
moderate from Wednesday to Friday. Wind speeds will be light
enough for modified afternoon see breezes along more sheltered
leeward slopes during this time period.

Forecast guidance continues to show stable conditions aloft with a
low trade wind temperature inversion height around the 6000 to
7000 foot level over the next five days. Precipitable Water
amounts will hover around 1 inch. Lower inversion heights and
moisture levels will tend to cap vertical cloud development,
limiting rainfall amounts. Expect continued isolated to scattered
showers mainly over windward and mountain areas in the overnight
to early morning hours. Isolated shower activity is possible over
some leeward areas for the same overnight time period.

&&

.AVIATION...
A broad area of high pressure NE of the islands and a stable air
mass will continue its dominance over the islands through Tuesday.
The trade winds will be breezy and gusty producing low level
mechanical turbulence over on the lee side of mountain ranges of
all islands. Therefore, AIRMET Tango remains in effect through at
least 020400 UTC.

VFR conditions will prevail overnight into Tuesday. Satellite IR
imagery shows scattered to broken low cloud coverage around Kauai,
including the county's leeward waters and waters east of Hilo and
the Puna district. Otherwise, it looks like scattered to locally
broken coverage. Do expect some increase in clouds and showers in
the coming hours but mountain obscuration is not expected. Only
brief MVFR ceiling and vis can be expected with these low clouds
favoring the windward and mountain areas. So far, weather radar
is detecting widely scattered showers with these clouds. Tops are
around 10k feet area wide with isolated tops at 15k to 20k feet
with the showers over the adjacent leeward waters of Kauai and
Oahu.

&&

.MARINE...
High pressure northeast of the state will keep fresh to strong
trades through Tuesday, before lowering to moderate levels
Wednesday and Thursday. The trades should increase a notch
beginning late Friday and hold through the weekend at moderate to
locally strong levels. A Small Craft Advisory (SCA) remains in
effect for the Kaiwi Channel, windward Maui and leeward Oahu
waters through 6 am Tuesday. A SCA remains in effect for the
typically windy waters around Maui and the Big Island through 6 pm
Tuesday, and this may need to be extended through Tuesday night
with the morning forecast package. Winds should drop below SCA
levels across all waters by Wednesday.

Small swells out of the south, southeast and southwest will
continue to produce small surf along south facing shores
throughout the week. A slightly larger long-period south swell is
expected this weekend, with surf heights rising to above the
summertime average. Surf along east facing shores should hold
steady through Tuesday, then lower during the middle part of the
week as the trades over and upstream of the state weaken. A small
northeast swell will give east shore surf a bit of a boost
Thursday into the weekend. A small 2 foot northwest swell will be
possible along north facing shores Wednesday and Thursday.

&&

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

Small Craft Advisory until 6 AM HST Tuesday for Oahu Leeward
Waters-Kaiwi Channel-Maui County Windward Waters.

&&

DISCUSSION...Bohlin
AVIATION...Lau
MARINE...Jelsema