568
FXHW60 PHFO 061947
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
947 AM HST Mon May 6 2024

.SYNOPSIS...
Breezy easterly trade winds will decrease to moderate levels by
this afternoon. A weak upper-level disturbance will drift over the
islands today, enhancing passing showers with a few thunderstorms
possible over the Big Island. An unstable band of clouds and
showers from an old front, followed by another, potentially
stronger, upper trough moving into the region, will keep wet
weather in the forecast lasting into the weekend.

&&

.DISCUSSION...
Current radar imagery shows scattered to numerous showers riding
into the windward and mountain slopes of all islands this morning.
Some of the stronger showers are drifting over into the drier
leeward areas. Water vapor satellite imagery continues to show a
weakening upper-level low slowly drifting from west to east across
the island chain. This feature will produce enough instability to
keep wet trade winds in the forecast today with isolated thunderstorms
over the Big Island this afternoon/evening as it tracks eastward
across the state.

At the surface, a 1030 mb high remains far north of the island
chain and will continue to produce breezy easterly trade winds
across the state through the morning hours. Wind speeds will taper
down through the day, becoming more moderate by this afternoon,
as the high pressure system drifts eastward away from the state.
Expect light to moderate easterly trade winds to continue through
the rest of the week with a hybrid pattern of trade winds and
sea/land breezes over terrain-sheltered leeward areas.

Wetter than normal conditions remain in the forecast for all
islands through the majority of this week. While Tuesday will
trend a bit drier, wetter weather will return for Wednesday and
Thursday as the remnants of an old East Pacific cold front drift
into the islands on the trade winds. Global models continue to
show an upper-level trough diving down over the state on Thursday
and Friday, along with a surface trough reflection. The models
still differ on the details, but this would keep enhanced showers
in the forecast into the weekend, with the potential for some
heavy downpours and chance of thunderstorms. Will continue to see
how this scenario evolves over the next couple of days and refine
the forecast as needed.

&&

.AVIATION...
Breezy easterly trade winds will persist through today, with
clouds and showers favoring windward and mauka locations. MVFR
conditions will be possible in any heavier showers. VFR conditions
will prevail elsewhere. Although confidence is low, instability
associated with an upper level low passing overhead could lead to
an isolated thunderstorm or two over the Big Island this
afternoon.

AIRMET Tango is in effect for moderate turbulence aloft (FL280-FL380)
as the tail end of an upper level jet streak stretches overhead.
Conditions should improve by this evening as the upper level jet
moves off to the east of the state.

AIRMET Sierra may be needed this evening if shower and low level
cloud coverage increase sufficiently.

&&

.MARINE...
Fresh to strong trade winds will slowly ease through Wednesday as
a 1029 mb high nearly 850 nm north of the islands moves off to the
northeast. A Small Craft Advisory (SCA) is in effect for the
typically windy waters around the Big Island and Maui County,
while borderline winds will remain in place elsewhere today. As
winds decline to moderate to locally fresh strength late Tuesday,
the SCA will be dropped entirely. A surface trough will form north
of the state on Wednesday, and this feature may drift southward
over the islands, leading to a disruption or further decrease in
trade winds.

Pulses of south to southwest swell are due this week, with High
Surf Advisory (HSA) conditions expected by Thursday. The PacIOOS
buoy off of Lanai is still showing some inconsistent energy in the
16 to 18 second range, but recent surf observations prompted a
lowering of forecast surf on south shores through Wednesday.
Forerunners from a larger and longer lived south-southwest swell
will arrive Wednesday, and surf is expected rise to the HSA level
during the peak of the swell Thursday and Friday.

A small northwest swell will build today and persist through
midweek. The NOAA buoys to the northwest are showing a swell of
around 3 feet, while the swell at the Hanalei PacIOOS buoy has
risen to over 2 feet at 15 seconds this morning. Expect this swell
to continue to spread down the island chain today, peak Tuesday,
and decline late Tuesday and Wednesday. Wind-driven waves of 7 to
8 feet at 8 to 9 seconds will maintain rough east shore surf above
the May average today. As trade winds decline over the next few
days, these seas will gradually decline to around May average by
Tuesday, then drop to below average for the rest of the week.

&&

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

&&

$$

DISCUSSION...TS
AVIATION...Farris
MARINE...Wroe