Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/06/23

Area Forecast Discussion

National Weather Service Honolulu HI

 341 PM HST Wed Apr 5 2023

.SYNOPSIS...
Moderate to locally breezy trade winds will prevail through the
week along with variable coverage of high clouds. Rainfall will
be focused across windward slopes, with an increase in shower
activity possible this weekend.

&&

.DISCUSSION...
An increasingly stable trade wind weather pattern prevails.
Easterly trade winds are holding at breezy levels this afternoon
as firm surface ridge has become established nearly 600 miles
north of the state. A sharp upper level trough a couple hundred
miles west of the islands continues to send thin high clouds over
the region, but otherwise its impact is waning. Aircraft data from
Kauai, which is closer to the upper trough, indicate increasing
stability as the mid and upper levels of the atmosphere warm,
while aircraft data and a recent sounding elsewhere indicate a
building inversion at 5,000 to 7,000 ft. A small pocket of low
level moisture has been producing modest rainfall on windward Big
Island today and has sparked a few heavier cells on the upper
slopes of Mauna Loa this afternoon, while little shower activity
has been noted elsewhere. Expect showers to diminish on the Big
Island this evening with an uptick in rainfall on Kauai and
possibly Oahu.

Breezy and rather stable trade wind weather is expected Thursday
and Friday. The surface high will meander in a similar position,
keeping the breezy easterly trade winds in place. An upper level
ridge will sit over the state, nudging the upper level trough a
bit westward and producing stability. This points toward a typical
pattern of mainly windward showers and, aside from a few
afternoon showers across the Kona slopes of the Big Island,
rather dry conditions for most leeward areas. The upper trough
will continue to send thin high clouds over the region.

Heading into the weekend, trades will ease a notch and shower
chances may increase. Trades will decline as the surface ridge to
the north is eroded by a passing North Pacific front. The upper
level pattern supporting this front will likely capture and the
upper level trough and pull this weakening feature over the state.
As a result, we will likely experience a decrease in stability
again, raising the possibility for an increase in shower activity.
Increasing trade winds and more stable conditions are expected
early next week.

&&

.AVIATION...
High pressure northeast of the state will keep moderate to breezy
trade winds in place during the next 24 hours and beyond. Passing
showers will primarily be limited to windward slopes and coasts.

A strong subtropical jet over the area will bring widespread
upper level clouds and turbulence. AIRMET Tango remains in effect
for moderate upper level turbulence over the entire state and
will likely remain in place through the night. AIRMET Tango is
also in place for moderate low level turbulence over and downwind
of the terrain due to the breezy trade winds.

&&

.MARINE...
Fresh to locally strong trade winds have returned due to an
elongated ridge of high pressure north and northeast of the
state. This ridge will shift south tomorrow and gradually weaken
into the weekend, easing trades briefly. A Small Craft Advisory
remains in effect for the windier waters from Oahu to the Big
Island through tomorrow, however some zones may dropout if winds
ease faster than anticipated. A new high will build north of the
state by early next week, strengthening trades once again.

Choppy surf along east facing shores will remain elevated due the
tradewind swell generated locally and upstream of the state.
Guidance shows this holding each day through the rest of the week
and dropping a touch over the weekend as trades ease slightly.

Small surf is anticipated for north and west facing shores through
the rest of this week, with the exception of some trade wind
energy wrapping into north shores. For the extended, there is a
potential for a short/medium-period northerly swell that would
arrive locally early next week and linger through midweek.

Background energy will keep surf along south facing shores will
remain small for the foreseeable future.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Thursday for Oahu Leeward
Waters-Kaiwi Channel-Maui County Windward Waters-Maui County
Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-
Big Island Leeward Waters-Big Island Southeast Waters.

&&

$$

DISCUSSION...Wroe
AVIATION...Kino
MARINE...Almanza