Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/25/23

Area Forecast Discussion

National Weather Service Honolulu HI

 346 PM HST Fri Mar 24 2023

.SYNOPSIS...
Building light to moderate trade winds will bring increasingly
settled weather and lower humidity tonight into Saturday, with
just a few windward showers expected. Winds will veer to the
southeast Sunday and Monday, but a mostly dry weather regime will
continue. A slow-moving front will bring the potential for
increased showers late Tuesday into Thursday.

&&

.DISCUSSION...
A somewhat unstable sea breeze regime prevails this afternoon. A
weakening surface low centered about 750 miles is drifting
northward, and a weak surface ridge continues to build roughly 125
miles north of Kauai. Moderate easterly winds in place near the
Big island veer southeasterly elsewhere, largely placing the rest
of the island chain under light winds in the wake of the Big
Island. The building low- to mid-level ridge has brought hints of
a low level inversion on the afternoon soundings and recent
aircraft data, while a departing upper-level trough just east of
the state is maintaining some instability aloft. As a result, a
slightly unstable sea breeze regime is in place this afternoon,
which has triggered interior clouds and spotty showers on all
islands and a few thunderstorms on the western slopes of Mauna
Loa. Humid conditions persist, as dew points hover in the lower
70s. Expect shower activity to decrease late this afternoon as
daytime heating wanes.

Easterly trade winds will return from east to west tonight and
Saturday and will persist into Sunday. The trades will be driven
by strengthening low- to mid-level ridging building to the north
and northeast of the state as the low lifts away from the region.
The mid-level ridge will be strong enough to produce rather stable
conditions that will focus modest rainfall over windward slopes,
and a drier air mass will bring relief from recent humidity as dew
points fall into the mid 60s. Expect another round of thin high
clouds on Saturday due to the lingering jet stream aloft near the
islands.

Trades will ease and veer southeasterly late Sunday and Monday as
another front approaches from the northwest. The GFS and ECMWF are
showing this front stalling about 100 to 200 miles northwest of
Kauai with a mid-level ridge near Kauai. A modest increase in
shower activity will be possible over the western end of the
island chain, mainly due to afternoon sea breezes, but heavy
rainfall looks to be unlikely at this time.

Wetter conditions are favored heading into the middle of next
week. Inconsistencies between recent runs of the GFS and ECMWF are
keeping the details uncertain, but expect a slow-moving front to
reach Kauai as early as Tuesday night, then move down the island
chain through Thursday or next Friday. Trade winds will be
disrupted ahead of the front, and instability aloft will have the
potential to produce heavy rainfall. Stay tuned.

&&

.AVIATION...
Sea breezes today with an unstable atmosphere has led to some
clouds and showers over interior sections of the islands with a
few isolated thunderstorms. Chances for showers and isolated
thunder will continue this afternoon before diminishing this
evening as the sun sets and the daytime heat driving the shower
development disappears. After the sun goes down, clouds and
showers should clear out and land breezes are expected to take
hold. Tomorrow morning could see modest strengthening of eastern
trade winds.

No AIRMETs are currently in effect.

&&

.MARINE...
Surface ridging will build north of the state through tonight,
allowing trade winds to return from east to west across the island
chain. The trades will reach moderate levels across the entire
marine area tonight, then become locally strong over the weekend
as the ridge lifts a bit further north. The windier zones around
Maui and the Big Island will likely reach Small Craft Advisory
(SCA) thresholds sometime Saturday. The trades will be on the
decrease by Sunday night as another front approaches from the
west. Light to moderate southeasterly winds, strongest over the
eastern half of the state, are expected for the first half of next
week.

A mix of small, medium-period northwest swells will keep some
small surf along north and west facing shores through Saturday.
A small, but longer-period northwest swell will build on Sunday,
giving a more noticeable boost to north and west shore surf Sunday
night and Monday. This swell will then lower Tuesday with only
small surf expected Wednesday. A new medium-period northwest swell
could give a slight boost to north and west shore surf late next
week.

Surf along east facing shores will hold steady through tonight,
with a slight boost expected over the weekend as trades
strengthen over and upstream of the islands, changing little
through the middle of next week, remaining at below normal levels.
A long- period northeast swell could give east shore surf a more
noticeable boost late next week. Only background south swell
energy is expected through late next week.

&&

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

&&

$$

DISCUSSION...Wroe
AVIATION...Tsamous
MARINE...TS