146
FXHW60 PHFO 091443 CCA
AFDHFO

Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
443 AM HST Thu May 9 2024

.SYNOPSIS...
Trade winds will diminish today through tonight as a broad
surface trough and upper disturbance move in. Added instability
associated with these features will lead to an increasing threat
for strong to severe thunderstorms and heavy rainfall late tonight
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. The wet pattern could continue through the latter half of
next week as another upper disturbance approaches.

&&

.DISCUSSION...
The morning water vapor imagery showed broad upper troughing over
the region with a strong shortwave 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 later today into tonight as the shortwave
trough closes off into an upper low and settles southward into
the area. 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 tonight, with
a transition to more of a widespread/statewide potential 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 over
interior/leeward areas 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 today and gradually weaken
heading into Friday. Daytime sea breezes and nighttime land
breezes are expected over wind-protected leeward areas.

Showers will continue to favor windward and mauka areas with the
greatest coverage and intensity during the late night and early
morning time period. MVFR conditions will accompany any of these
heavier showers. As sea breeze activity resumes by this afternoon,
clouds and showers will begin to develop across some leeward/interior
locations. In addition, a disturbance aloft will approach the
area later today, helping to enhance shower activity across the
state and bringing instability that may help to spark a few
thunderstorms near Kauai sometime tonight into tomorrow morning.

AIRMET Sierra is in effect through this morning for tempo
mountain obscuration across windward areas as a band of moisture
moves in from the east. This AIRMET may be needed periodically
throughout the next 24 to 36 hour period due to enhanced shower
activity.

&&

.MARINE...
A trough developing north of Kauai today will strengthen and
expand southward over the island chain tonight into Friday, then
linger through the weekend. As a result, winds will remain rather
light and below Small Craft Advisory thresholds. A strong
disturbance aloft moving overhead will bring a threat for strong
to severe thunderstorms late tonight through 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 through early next week.

A long-lived south swell will affect the islands during the next
several days, keeping south shore surf above the summertime
average. The surf is expected to peak below the High Surf
Advisory threshold of 10 feet today through Friday, then
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.

North shore surf will remain tiny today and tonight, followed by a
small reinforcing short-period north-northwest swell late Friday
through the 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 normal
levels through the middle of next week.

&&

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

&&

$$

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