837
FXHW60 PHFO 170801
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
1001 PM HST Tue Jul 16 2024

.SYNOPSIS...
Trade winds should gradually relax just a bit over the next few
days, as a surface high far to our north moves slowly northeast.
Dry and stable air over the state should limit windward showers,
which will favor the overnight and early morning periods. Isolated
afternoon showers can be expected to form on the sea breeze over
the lower slopes of leeward Big Island. A weak trough aloft moving
over the state from east to west this weekend could bring a minor
increase in showers for portions of the state. Stronger trades
are expected to return again early next week as the high over the
northeast Pacific strengthens and pushes south toward us once
again.

&&

.DISCUSSION...
1029 mb surface high 1400 mi NW of Kauai moving E very slowly.
Ridge extends SE from the high, 600 mi N of the islands. This is
maintaining breezy to locally windy trades. Over the next few
days the high will move very slowly NE and the ridge will weaken,
while a weak, stationary surface trough develops 600 mi NE of the
islands and lingers through Sat. This should allow the trades to
gradually relax just a bit. Starting Sunday, the trough will begin
moving W and weaken, allowing the now-stronger high to build back
toward the S, far N of the islands. This will allow locally windy
trades to return about Mon.

CIRA ProxyVis and GOES-derived TPW show rather dry air around the
state, with patchy stable low clouds and only a few mainly
windward showers. The inversion is just a little higher near the
Big Island, so a few more shower bands showing up over the BI
windward waters, but nothing out of the ordinary. Weak mid-level
ridging and warm temperatures aloft also dominate, so windward
rainfall should continue to be rather light overall for the next
few days. Models show a weak trough at 700 mb moving in from the
E over the weekend. Guidance shows this will be enough to raise
the inversion a bit, allowing for a minor increase in mainly
windward showers. Last couple afternoons have also seen a couple
of sea breeze showers form over the lower slopes of the leeward
Big Island and this general idea should continue as well. Most
other areas should remain rain-free.

&&

.AVIATION...
Breezy trades will continue through tonight, then gradually ease
through the end of the week. SHRA and low cigs will favor windward
and mauka areas and could bring brief periods of MVFR. Otherwise,
VFR will prevail.

AIRMET Sierra is in effect for mtn obsc for Oahu and Molokai and
may be expanded to the other islands at next issuance.

AIRMET Tango for mod low-level turb lee of island terrain remains
in effect and will continue through tonight.

&&

.MARINE...
Fresh to locally strong trades will weaken to moderate late
tonight into Wednesday as weak troughing develops northeast of the
islands. The Small Craft Advisory for the typical windier waters
of Maui County and the Big Island remains posted through early
Wednesday morning.

Existing long period south swell is slowly subsiding, the bulk of
energy now shifting toward the 13 to 15 second bands per the
latest buoy observations. Surf heights continue to run near or
just blow the High Surf Advisory (HSA) thresholds, however, surf
should continue to subside through the night and drop below
average through the day Wednesday. This swell will then slowly
decline during the latter half of the week, dropping to background
levels Friday into the weekend.

Surf remains choppy along east facing shores due to trades and is
also experiencing a very modest bump from a small northeast
swell. Surf along east facing shores should see a gradual decline
Thursday and Friday as trades winds ease and the northeast swell
energy dissipates. North facing exposures may see a tiny bump from
the combination of a small, medium period northwest swell and the
small northeast swell mentioned above tonight into Wednesday but
will quickly fade Wednesday night.

&&

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

&&

$$

DISCUSSION...R Ballard
AVIATION...Walsh
MARINE...Almanza