831
FXHW60 PHFO 030717
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
917 PM HST Tue Jul 2 2024

.SYNOPSIS...
The recent stagnant, relatively dry pattern under gentle trade
flow will persist through the holiday weekend. High pressure far
northeast of the islands will weaken in response to eastern
Pacific troughing. This will maintain light to gentle east trade
winds through the week. Upper level ridging over the islands,
along with easterly dry air, will ensure continued mainly clear
to partly cloudy skies with little to no statewide rainfall.
Shower behavior that brings any measurable rainfall will primarily
focus along windward slopes during nocturnal hours.


&&

.DISCUSSION...
The overall Hawaiian Island weather pattern will be controlled by
upper level ridging and a pair of quasi-stationary surface high
pressure cells thousands of miles north and northeast of the
state. The general early month synoptic set up will evolve with
the northeast high moving further away as troughing develops
between us and the high. This, in tandem with the other high cell
north of the islands drifting further west, will weaken the
downstream pressure gradient enough to generally hold light to
gentle east trades in play through the Independence Day holiday
weekend.

Upper to mid level ridging will remain over the central Pacific
and provide ample subsidence. This, along with a large dry air
mass moving around the base of eastern Pacific troughing and
advecting in across the area mid to late week, will provide the
main ingredients for continued dry and warm weather for Hawaii.
If NWP guidance holds true with the characteristics of this dry
air mass, it will fall within the lower 10th percentile for this
time of year (near 0.9 inch pwats compared to early July
climatology norm 1.3 inch pwats). The added subsidence will create
more clear, island-wide sunny skies. This will ultimately result
in warmer afternoon temperatures. Trades will introduce thicker
clouds and occasional typographically-enhanced low rainfall
accumulation showers over windward (mauka) zones during the
overnight and early morning hours. Leeward areas should remain
mostly to partly sunny with that rare light shower making its way
over the ridgeline. The lone exception to this rule will be those
warmth-of-the-day afternoon clouds/weak showers that will
inevitably form along leeward Haleakala and Big Island.


&&

.AVIATION...
Moderate to locally breezy trade winds will continue for the next
few days. A weakening band of low clouds and showers continues to
move westward over Kauai this evening. This shower band will
bring periods of MVFR conditions to north and east sections of the
island through the overnight hours. Elsewhere mostly VFR conditions
are expected.

AIRMET Sierra remains in effect for mountain obscuration across
north through east sections of Kauai.


&&

.MARINE...
High pressure northeast of the state will bring fresh to strong
trades through most of the week. By this weekend, the high will
weaken and move off to the northeast as surface troughing
approaches from the west, causing trades to decrease slightly
across local waters. A Small Craft Advisory is in effect through
at least Thursday morning for the windier waters and channels
around the Maui and The Big Island.

No significant south swells are expected during the forecast
period. However, a series of small south-southwest and southeast
swells will keep south facing shores from going flat.

Flat to tiny surf conditions will continue along north and west
facing shores through most of the week. East shore surf will be
close to seasonal levels through late this week as fresh to
strong east northeast trades persist over and upstream of the
islands. A fetch of strong northeast winds well off the California
coast should bring a small, medium period, northeast swell
Saturday into early next week. Some of this swell should wrap into
select north facing exposures as well.

Water levels running roughly 0.6 ft higher than normal around the
Big Island, combined with the new moon tides, could cause minor
flooding issues through Saturday, with peak water levels expected
Thursday. Recent observations from Hilo Bay and Kawaihae show
water levels getting over 1 foot above the Mean Higher High Water
(MHHW), thus a Coastal Flood Statement remains in effect for the
coastal zones around the Big Island.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.


&&

$$


DISCUSSION...Blood
AVIATION...Bohlin
MARINE...Powell