464
FXHW60 PHFO 081937
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
937 AM HST Wed May 8 2024

.SYNOPSIS...
Expect moderate trades over the eastern islands through Thursday,
while lighter trades and leeward land and sea breezes prevail
over the western islands. Showers will favor windward slopes and
coasts at night and interior and leeward areas each afternoon.
Thunderstorms are possible Friday and Saturday as an upper
disturbance moves through. Conditions should improve Sunday
through early next week.

&&

.DISCUSSION...
High pressure far north of the main Hawaiian Islands drives
moderate trades across local waters this morning. Satellite loop
shows broken to overcast low clouds across windward areas while
leeward areas appear to have scattered low clouds to clear skies.
Overnight soundings depict seasonal amounts of PW, between 1.3 and
1.5 inches of PW, and a neutral to slightly unstable airmass.
Subsidence inversions are noted between 5500 and 6500 feet, acting
as deterrents to widespread and intense shower development. Radar
shows scattered light to moderate showers beneath trade wind
cloud cover.

A front far northwest of the islands will shift southeastward
over the next couple of days, eventually weakening into a broad
trough across the islands on Friday. Trades will ease over the
next few days in response. Expect moderate trade winds over the
eastern islands today and Thursday, while lighter trades allow
development of land and sea breezes across leeward areas of the
western islands. Through Thursday, expect showers to favor
windward and mauka areas overnight and during the morning, then
transition over to interior and leeward areas each afternoon into
the early evening. As the boundary layer flow becomes light and
variable Thursday night, most showers should remain offshore.
Models show trades will decrease further on Friday, allowing for
sea breeze development statewide. Trades may strengthen over the
weekend as the broad trough gradually weakens. By early next week,
another front northwest of the state will cause surface flow to
veer to southeasterlies across the western islands while trade
flow persists across the eastern islands.

Models show an upper low will move across the chain Friday
through Saturday. Associated cold air aloft will destabilize our
airmass and introduce the possibility of thunderstorms. At this
time, predicted PW does not appear to be high enough to fuel a
widespread heavy rain threat. However, brief heavy downpours
associated with possible thunderstorms would cause minor flooding
impacts. We will monitor model depictions over the next few days
and issue appropriate watches if needed. Models also depict a
potential for severe thunderstorms, with steep lapse rates, high
CAPE, and strong bulk shear. If these conditions were to develop,
stronger thunderstorms would be capable of producing hail and
strong gusty winds. Expect a return of a hybrid trade wind
pattern by Saturday night, featuring windward and mauka showers
at night, followed by interior and leeward showers during the
afternoon and early evening hours.

&&

.AVIATION...
Light to moderate trades are expected today with localized sea
breezes developing later this morning for select leeward areas.
Bands of light showers will continue to favor windward and mauka
areas and be most active during the overnight hours. Over leeward
areas, sea breezes will bring an increase of interior clouds and
scattered showers this afternoon. Land breezes may also help to
clear out cloud cover across leeward areas overnight. Brief MVFR
conditions are to be expected in passing showers, otherwise VFR
conditions will prevail statewide.

No AIRMETs are in effect at this time. A subtropical jet passing
just south of the state could bring light to moderate turbulence
between FL300 to FL350 around the Big Island this afternoon
through tonight.

&&

.MARINE...
Moderate trade winds will weaken over the next several days as
high pressure northeast of the state moves further away and a cold
front approaches the islands from the northwest. The front will
weaken into a trough over the islands on Friday. Wind speeds
should ease and become light to gentle Friday and Saturday with
southeast flow over the eastern half and northeast to east flow
over the western half of the state. Gentle to locally moderate
east to southeast flow looks continue into the early half of next
week across the coastal waters. Additionally, an upper level low
will approach and move across the island chain. This will likely
trigger heavy showers and possible thunderstorms, especially over
the smaller islands Friday and Saturday.

Surf along south facing shores will pick up as the weekend
approaches. Forerunners from a larger and longer lived south-
southwest swell are expected to arrive later this afternoon. Surf
could reach High Surf Advisory (HSA) criteria Thursday or Friday
before declining over the weekend.

Meanwhile, the current northwest swell will continue to decrease
to tiny conditions through tomorrow followed by a reinforcing
short- period north northwest swell Friday and Saturday. Surf
along east facing shores is expected to remain small as trade
winds are expected to be light to locally moderate through the
rest of the week.

&&

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

&&

$$

DISCUSSION...Powell
AVIATION...Kino
MARINE...Bedal/Wroe