912
FXHW60 PHFO 090706
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
906 PM HST Wed May 8 2024

.SYNOPSIS...
Trade winds will diminish Thursday through the weekend as a broad
surface trough and upper disturbance move in. Added instability
associated with these features will lead to an increasing threat
for strong thunderstorms and heavy rainfall late Thursday through
Saturday. Although the thunderstorm potential will lower Sunday
into early next week, plenty of moisture lingering combined
afternoon sea breezes and a broad surface trough nearby will
support afternoon showers over our interior and leeward areas each
day. This potential may continue through the latter half of next
week as another upper disturbance approaches.

&&

.DISCUSSION...
The evening water vapor imagery showed broad upper troughing over
the region with a strong shortwave trough digging southeastward
toward the area. The local winds will respond and diminish over
the next 24-Hrs as the attendant cold front passes to the north
and broad surface troughing evolves over the islands. The short-
term guidance has initialized well with this pattern and depicts
strong upper height falls late Thursday as the shortwave trough
closes off into an upper low as it settles southward into the area
Thursday night through Friday. MUCAPES of 1000 to 2000 J/Kg
combined with effective deep layer shear values of 35 to 45 knots
will support a few strong to severe thunderstorms and locally
heavy rainfall that could lead to flash flooding through this
period. Impacts could begin over the western end of the state as
early as Thursday evening/overnight hours, with a transition to
more of a widespread/statewide event Friday through Saturday.

Guidance shows the upper low beginning to weaken as it lifts off
to the northeast later this weekend, which will support a
diminishing threat of thunderstorms. The rainfall chances,
however, will likely linger as the aforementioned broad surface
trough remains over or nearby to the west Sunday through next
week. Expect the light to moderate east to southeast low-level
flow to persist, which will allow the land and sea breeze regime
to hold for most areas. This combined with a sufficient amount of
moisture will keep the rainfall chances up each day, especially
through the afternoon and early evening periods with the sea
breezes. The wet pattern could persist through the second half of
the week as another upper low drops southward into the area
drawing up deep tropical moisture over the state.

&&

.AVIATION...
Light to moderate trades will persist through Thursday with day
time sea breezes and night time land breezes expected over wind-
protected leeward areas.

Showers will continue to favor windward and mauka areas with an
uptick of showers expected later tonight into Thursday morning as
a band of moisture approaches from the east. As this moisture
band moves in, MVFR conditions will be possible for windward and
mountain areas with VFR conditions prevailing across leeward areas
through Thursday morning. For tomorrow, sea breeze activity will
resume and a disturbance aloft will begin to approach the state,
which could enhance shower activity in the afternoon.

No AIRMETs are in effect at this time. AIRMET Sierra will be
possible late tonight into Thursday morning for windward and
mountain areas as a band of moisture moves in.

&&

.MARINE...
Moderate to locally fresh trade winds will continue to decline as
a strengthen surface trough north of Kauai weakens the local
pressure gradient. The trough will strengthen and expand over the
islands Thursday night and Friday and linger into the weekend,
disrupting the local winds. A strong disturbance aloft moving
overhead will bring a threat for strong to severe thunderstorms
mainly Friday into Saturday. These thunderstorms will have the
potential to produce dangerous wind gusts, hail, and frequent
lightning. Moderate east to southeast trade winds will gradually
rebuild Sunday or Monday.

A long-lived south swell will affect the islands during the next
several days. Long-period forerunners have arrived at the
nearshore buoys and will continue to build overnight. South shore
surf is expected to rise above the summertime average, but will
likely peak just below the High Surf Advisory level of 10 feet
Thursday afternoon through Friday. We will continue to monitor
the buoys overnight in case the swell comes in bigger than
anticipated. This long-lived swell will gradually decline
Saturday through Tuesday. A series of overlapping long-period
south swells will give another sizable boost to south shore surf
Wednesday through late next week.

The current northwest swell will decrease to tiny levels
Thursday and Friday, followed by a small reinforcing short-period
north-northwest swell this weekend. A small long period northwest
swell will build Sunday night, giving north shore surf a boost
early next week. Surf along east facing shores will be well below
May average through the middle of next week.

&&

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

&&

$$


DISCUSSION...Gibbs
AVIATION...Farris
MARINE...Jelsema