460
FXHW60 PHFO 231345
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
345 AM HST Sun Jun 23 2024

.SYNOPSIS...
High pressure north of the state will maintain breezy trade winds
the next few days. Showers will primarily favor windward coastal
and mauka slopes. Trades will slightly weaken around the middle of
the week with a possible increase in late week shower activity.


&&

.DISCUSSION...
The downstream pressure gradient from a 1030 mb high centered
approximately 950 miles north of Kauai remains tight enough
across the island chain to continue breezy trades well into the
week. The Hawaiian Islands will remain under the stabilizing
influence of mid-level ridging as the area falls along the
southeasterly periphery of the 700 mb ridge positioned to the
northwest. Early day water vapor satellite imagery depicts a
drier resident air mass over the islands. This is verified by
a quieter radar of widely scattered weak trade showers.

While morning sounding precipitable waters fall in-line with late
June climatology numbers (1.3-1.4 inch pwats), mid to upper level
northeasterly drier air advecting into the state will limit
overall shower activity today; light, isolated showers primarily
confined to windward mauka slopes. Slightly higher mid-level
moisture advecting in Monday, along with a 6-7 k ft fairly
saturated layer, may be enough to increase shower coverage and
produce a few hundredths more rain in those communities that
typically stay wet during a normal trade flow pattern. Little to
no movement of the lower and upper ridge planted north of the
islands through Tuesday ensures breezy trades under partly to
mostly cloudy windward skies...mostly to partly sunny leeward
skies. High pressure at all levels begins to transition east
during the latter half of the week. This will weaken the lower
level pressure gradient enough to subtly suppress trade flow to
more gentle magnitudes, although easterlies will still remain
breezy along ridge lines and within more east-to-west orientated
valleys. Lowering mid to upper heights, with periodic ribbons of
higher moisture passing to the west, will increase shower
frequency and areal coverage later in the week. Higher confidence
in the development of an upper level disturbance east northeast of
the islands will certainly boost weekend rain chances as we close
out the month of June.


&&

.AVIATION...
Breezy to locally windy trades will continue through Monday.
Showery cloud bands embedded in the trade flow will produce
periods of MVFR conditions across windward/mauka areas of each
island, particularly through the overnight and early morning hours
each day. Conditions will improve through the late morning and
afternoon periods.

AIRMET Sierra remains in effect for tempo mountain obscuration
for windward slopes of most islands, which will likely continue
through the early morning hours.

AIRMET Tango remains in effect for mod low-level turb over and
downwind of island terrain due to the breezy trade winds. This
AIRMET will continue through Monday.


&&

.MARINE...
Surface high pressure, centered around 850 nm north of the state,
will remain nearly stationary through early this week and help
generate strong easterly trades. A Small Craft Advisory will
remain in effect for all local waters through Monday night. Trades
are expected to then decrease slightly Tuesday through midweek as
the aforementioned surface high drifts northeast, away from the
islands.

Surf along east-facing shores will remain rough and choppy through
Monday due to the strong trades locally and upstream of the state.
A gradual downward trend is expected Tuesday through mid week.

Expect slightly elevated surf along south-facing shores through
Tuesday (though still near or below seasonal norms) as a small,
medium to long period, south swell moves through. The swell has
already shown up on the Barbers Point Buoy with energy in the
14-16 second period range. However, this should be short-lived,
with a downward trend expected by Tuesday night. Despite a
blocking high that has set up over our typical swell window
southeast of New Zealand, a gale has formed northeast of this high
with the head of the fetch aimed at the islands within the 180 to
200 degree directional band. Given the shorter travel distance,
surf associated with this source should trend up late this week.

Nearly flat conditions will exist along north-facing shores
today. A small, medium period, northwest swell will bring tiny
surf to these shores late Monday through mid week.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Monday for all Hawaiian
waters-


&&

$$


DISCUSSION...Blood
AVIATION...Gibbs
MARINE...Thomas