Heavy Rain in Hawaii, July 5, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
931 AM HST Sun Jul 5 2020

.SYNOPSIS...
Light to moderate easterly trade winds will be overpowered by
afternoon sea breezes, leading to increased clouds and spotty
showers over leeward areas. Trade winds will gradually increase
on Monday and become locally breezy Tuesday into next weekend.
The stronger trades will promote a typical summertime weather
pattern, focusing rainfall along windward slopes and producing
afternoon showers over leeward Big Island.

&&

.DISCUSSION...
Light to moderate easterly trade winds have largely pushed away
the batch of moisture that affected the state during the past
day. However, a few showers remain hung up along the southeast
slopes of the Big Island and over the mountains of windward
Kauai this morning. The rest of the state is experiencing a lull
in showers under a narrow slot of relatively drier air ahead of
another band of moisture approaching from the east. Models suggest
that this band will enhance windward rainfall late this afternoon
into tonight. Meanwhile, sea breezes will overpower the trades
across most leeward areas, leading to afternoon clouds and spotty
showers, especially across sheltered leeward terrain including the
burn area in Waianae Valley. The ridge aloft over the state
remains rather weak, which means that some afternoon showers could
be briefly heavy.

Easterly trade winds will remain somewhat suppressed tonight and
will begin a gradual increase Monday afternoon. The incoming band
of moisture will produce showers along mainly windward slopes
tonight, possibly into early Monday morning on Kauai. Leeward
shower activity will decrease during the evening as lingering
convection dissipates and gives way to land breezes. Aside from
trailing moisture over Kauai, showers should be less active on
Monday as a drier and more stable airmass moves in from the east.

Trade winds will become locally breezy on Tuesday as high pressure
builds far north of the state. A typical summertime weather
pattern is expected into next weekend. Rainfall will be largely
focused over windward slopes, while afternoon showers develop each
afternoon over leeward Big Island. A ridge aloft will maintain
stable conditions.

&&

.AVIATION...
VFR conditions prevail at most TAF sites this morning. Periods of
MVFR conditions are possible at times today mainly for windward
locations such as PHTO and PHLI. Windward slopes and mountains may
also see periods of MVFR conditions through the evening hours.
Occasional MVFR conditions are also possible at PHNY through the
evening hours. Daytime heating along with sea breeze convergence
may cause some MVFR conditions this afternoon and evening over
some interior and leeward locations as well.

&&

.MARINE...
Light to moderate east-southeast winds will hold today as a weak
trough west of Kauai continues westward away from the state. Winds
will remain light enough for afternoon sea breezes to develop for
some leeward coastal areas today. A return of a more typical trade
wind pattern is anticipated Monday with winds reaching the moderate
to fresh range. Winds should ramp up to fresh to strong by Tuesday,
likely requiring a Small Craft Advisory for the typical windier
waters around Maui County and the Big Island. The advisory may need
to be expanded to additional marine areas as the trades continue
to increase though the week. Seas will also approach advisory level
(10 ft) over the Alenuihaha Channel and waters south of the Big
Island by the end of the week.

Surf along south facing shores will remain small through the week,
with mainly a mix of small south and south-southeast energy. For
the extended, guidance depicts a a solid area gales setting up in
the Tasman Sea through the first half of the week, which could
result in an uptick in surf locally by mid July.

Surf along east facing shores will remain small through Tuesday,
then gradually trend up through the rest of the week as the trades
increase locally and upstream of the islands across the eastern
Pacific. Surf along north facing shores will remain small through
the upcoming week, however some spots exposed to trade wind wrap
may bump up a bit through the second half of the upcoming week.

&&

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

&&

DISCUSSION...Wroe
AVIATION...Burke
MARINE...TS