160
FXHW60 PHFO 140659
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
859 PM HST Sat Jul 13 2024

.SYNOPSIS...
A large area of high pressure generally north of the Hawaiian
Islands will hold the next several days. This will maintain the
ongoing typically dry summertime trade wind pattern. Windward and
mauka area light showers will primarily occur during the early
morning and overnight hours. A vicinity upper level disturbance
northeast of the state will weaken trades to more moderate speeds
and increase more island-wide rain chances during the second half
of next week.


&&

.DISCUSSION...
There remains little variance in forecast philosophy under this
near static Central Pacific synoptic pattern. Stable conditions
will stay in play in response to ridging holding north of the
state. Summertime dry trades persist as a pair of surface highs
centered northwest and northeast of the islands drive primarily
fresh to locally strong easterlies through Sunday. Relatively
lower inversion 5-6k foot heights will result in a more shallow
boundary layer, in tandem with dry mid to upper level moisture (<
30% RH) advecting in across the chain, nearly guarantees a stable
enough island environment that will generally support windward and
mauka cloudier skies and occasional showers. The usual suspect
caveats of cloudier, slightly more wet afternoon Kona and Ka`u
slope conditions with infrequent leeward sprinkles and partly
cloudy skies riding over local area ridge tops still apply.

The development of an upper level disturbance forming in the
middle of the northern ridging will be the impetus to gradually
weakening trades. The surface reflection of weak troughing, along
with the proximity of a subtropical jet, may work in favor of
increasing more areawide pockets of better organized shower
activity next week. The main question marks to increased shower
activity relieving us from this recent dry spell will be whether
or not there will 1) be ample column moisture within a deepened,
marginally-destabilized boundary layer and 2) the location of the
upper disturbance in relation to the islands. The wettest period
is shaping up to be late in the week, or Thursday and Friday.
Late week inversions are progged to be slightly higher (closer to
6.5k ft), lower level lapse rates the greatest (5 to 6 deg C in
lowest 3 km) within a more moist air mass (> 80% RH). These three
elements best come in-line over Big Island and Maui Counties as we
close out the traditional work week.


&&

.AVIATION...
Breezy to locally windy trades will continue over the next few
days. SHRA amd low cigs will favor windward and mauka locations
with a few SHRA making it leeward. Some brief MVFR conds are
possible in SHRA, otherwise VFR conds should generally prevail.

AIRMET Sierra will go into effect for mtn obsc for N through SE
sections of the island chain at 10Z. Low cigs and a slight
increase in SHRA are expected through the night.

AIRMET Tango for mod low-level turb lee of terrain is in effect
and will likely be needed for the next several days due to the
strong trades under a strong inversion.


&&

.MARINE...
The Small Craft Advisory (SCA) will remain in effect through
Monday. This SCA will cover all Hawaiian Coastal Waters tonight,
and then decrease in coverage on Monday to the typical windier
waters near Maui County and the Big Island. A High Surf Advisory
remains in effect for the south facing shores of all islands
beginning Sunday morning.

A strong high pressure ridge remains north of the islands, and
will continue to drive fresh to locally strong trade winds to the
region into the new week. As mentioned above, the SCA has been
extended for the typical windier waters near Maui County and the
Big Island through Monday, while winds over the remaining coastal
waters are expected to drop below advisory levels overnight.

The current long period south swell continues to fill in, with
surf on the increase. Expect High Surf Advisory level surf to
spread across south facing shores on Sunday, and last into Monday.
West facing shores will see a decent south swell wrap, boosting
surf heights as well, with the Big Island west facing shores
possibly reaching HSA levels on Sunday. A gradual downward trend
is expected Tuesday through midweek.

Due to the strong trade winds upstream of the state, surf along
east facing shores will remain rough and choppy through early
in the new week. A downward trend is possible around midweek as
the upstream fetch weakens and the local trades begin to ease.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory from 6 AM Sunday to 6 PM HST Monday for
Niihau-Kauai Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-
Kona-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai
Leeward South-Lanai Leeward-Lanai South-Maui Central Valley
South-South Maui/Upcountry-South Haleakala-Big Island South-Big
Island Southeast.

Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Big Island
Windward Waters.

Small Craft Advisory until 6 PM HST Monday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.


&&

$$


DISCUSSION...Blood
AVIATION...Walsh
MARINE...Bohlin