032
FXHW60 PHFO 041955
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
955 AM HST Tue Jun 4 2024

.SYNOPSIS...
Breezy trades will continue today, before easing Wednesday and
giving way to sea and land breezes Thursday and Friday. An upper
level trough will bring the chance for an isolated thunderstorm
over on the Kona slopes this afternoon. Otherwise, very dry
conditions will overspread the entire island chain Thursday
through the weekend, greatly limiting shower activity. Breezy
trades returning early next week should bring the return of some
windward showers.

&&

.DISCUSSION...
This morning`s satellite shows stable stratocumulus clouds moving
into windward areas this morning and is producing a few light
showers across the state. If we zoom out a little, altocumulus
clouds are seen east and northeast of the Big Island. These clouds
are associated with the isolated thunderstorms last night over
windward Big Island. 12Z sounding from Lihue and Hilo show very
steep mid level lapse rates due to a cold upper level trough over
the state. This upper level trough should gradually move northeast
and away from the state over the next 24 hours.

For today, although the atmosphere in the upper levels remain
unstable, at the surface we have a 1025 mb high centered northeast
of the state producing our breezy trade winds. A drier air mass
moving in today with a strong inversion at around 5500 feet
should keep shower activity fairly light and mainly focused over
windward areas. The one area of concern would be over the Kona
slopes of the Big Island. Day time heating combined with some
lingering upper level moisture will allow for showers and possibly
a few isolated thunderstorms to develop over the slopes. Any
showers or thunderstorms that do develop on the Big Island,
should weaken during the evening and dissipate overnight.

Trades are expected to weaken another notch on Wednesday as the
ridge of high pressure north of the state drifts closer to the
state. By Thursday, the ridge of high pressure will be very close
to the state and we should the winds weaken another notch. Earlier
runs of the ECMWF and GFS were in good agreement for light and
variable winds on Thursday, but the latest ECMWF is now showing a
light trade wind pattern. Although the trades will likely still be
light enough for sea breezes to develop during the day time. From
Friday into Saturday, winds will likely pick up a touch and we
should see a light to moderate trade wind pattern.

As far as precipitation, there will be little of it through the
weekend. The Kona slopes should have a chance for showers each
afternoon, but as a drier and very stable air mass moves in over
the next few days, any shower activity will remain light.
Elsewhere, with a strong mid level ridge overhead and drier than
normal low level moisture, showers are not expected including
windward areas. So overall, we should see plenty of sunshine with
very few rain drops over the next several days.

&&

.AVIATION...
Breezy easterly trades will continue through today, then
gradually weaken into tomorrow as the pressure gradient relaxes.
Clouds and showers will favor windward and mauka locations with
brief periods of MVFR conditions possible. Lingering elevated
atmospheric instability over the state will allow for the
potential development of isolated thunderstorms over interior and
upslope sections of the Big Island this afternoon and evening.
Stability will increase heading into Wednesday as mid level
ridging strengthens over the state, cutting off the thunderstorm
potential.

AIRMET Sierra is in effect for mountain obscuration for windward
Big Island and N thru SE sections of the smaller islands. This
AIRMET will likely be needed through mid to late morning before
conditions improve into the afternoon.

AIRMET Tango for low level turbulence lee of island terrain
remains in effect. This AIRMET will likely be needed through
today, but will be cancelled by Wednesday morning as winds below
the inversion decrease.


&&

.MARINE...
High pressure to the far northeast and northwest, with a ridge
between the two, will maintain fresh to strong trade winds today,
and as a result a Small Craft Advisory (SCA) remains in effect
for all waters around the Big Island and Maui County, as well as
selected areas around Oahu and Kauai. The ridge is expected to
weaken through the day, and anticipate the SCA being trimmed back
to the typical waters around Maui County and the Big Island
through tonight. The ridge is expected to weaken and sink
southward over the islands Thursday into Friday, which will lead
to a significant decrease in the trades, which will likely lead
to the SCA being dropped altogether. Over the weekend, the ridge
is expected to lift northward, allowing moderate trades to return
from south to north.

The active south Pacific will continue to generate southerly
swells here in the islands through the middle of the month. The
current south-southwest swell got another pulse overnight but
remains just below High Surf Advisory (HSA) criteria. This swell
will gradually decline through Thursday, followed by a reinforcing
south-southwest swell late Thursday and Friday that will produce
south shore surf around seasonal average. A larger swell is
expected to move through the islands this coming weekend, which
will likely be near or at HSA levels of 10 feet. An potentially even
larger swell is looking increasingly likely late next week that
would bring surf well above advisory levels.

A small northwest swell has continued to fill in overnight and
looks to hold today. Another pulse from the northwest will follow
Wednesday into Thursday. The fresh to strong trade wind flow is
producing rough choppy elevated seas but the wind waves will
diminish significantly after Wednesday coinciding with the light
winds through the weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County
Windward Waters-Maui County Leeward Waters.

Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters-Big Island Southeast Waters.


&&

$$


DISCUSSION...Kino
AVIATION...Farris
MARINE...M Ballard