235
FXHW60 PHFO 161303
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
303 AM HST Mon Sep 16 2024

.SYNOPSIS...
Moderate to locally breezy trade winds will prevail across the
islands through the work week and into the upcoming weekend. A
slug of deep moisture will bring an increase in trade wind showers
particularly to windward slopes and coasts as it moves from east
to west across the islands today and tonight. Typical trade wind
weather featuring mainly windward and mauka showers will return by
Tuesday and continue through the upcoming weekend.

&&

.DISCUSSION...
Currently at the surface, a 1030 mb high is centered around 1500
miles north-northeast of Honolulu, and is driving moderate to
locally breezy trade winds across the island chain early this
morning. Infrared satellite imagery shows partly to mostly cloudy
conditions across the state, with cloud coverage the greatest in
windward areas. Radar imagery shows numerous to widespread shower
activity over windward areas from Oahu eastward, with scattered
showers moving into windward Kauai. Main short term focus is on
rain chances during the next couple days.

High pressure north-northeast of the state will drift westward to
a location due north of the islands today, then remain nearly
stationary through Thursday, keeping moderate to locally breezy
trade winds in place. The high will shift eastward and weaken
slightly Friday through the upcoming weekend, which could bring a
slight easing in the trade wind speeds.

As for the remaining weather details, a mid-level trough will
bring a slug of deeper moisture from east to west across the
islands today and tonight. Showery weather can be expected in
windward areas as this batch of deeper moisture moves through. We
should see a return back to more typical trade wind weather
beginning this afternoon over the Big Island and by Tuesday
morning over Kauai. Typical trade wind weather featuring mainly
windward and mauka showers and the occasional leeward spillover
will then continue Tuesday through the upcoming weekend.

&&

.AVIATION...
High pressure centered far north of the state will maintain
moderate to breezy trades over the next few days. A plume of
deeper moisture is moving across the state this morning,
affecting primarily windward portions of the islands, though the
temperature inversion heights will remain elevated enough to allow
occasional showers to pass over island terrain into some leeward
areas. MVFR conditions, and isolated IFR, are expected in heavier
showers through the morning. Elsewhere, VFR conditions are
expected to prevail.

AIRMET Sierra is in effect this morning for mountain obscuration
due to low clouds and showers for windward portions of the state
except for Kauai, although it may need to be added later this
morning. These conditions will persist through the morning and
may improve by the afternoon.

With locally breezy trade winds prevailing across the state,
AIRMET Tango remains in effect for low-level turbulence over and
downwind of terrain. This AIRMET will likely continue through
tonight.

&&

.MARINE...
Moderate to locally strong trade winds will hold through
Thursday, as a strong surface high meanders far north of the
islands. A Small Craft Advisory (SCA) has been expanded for all
waters surrounding Maui County and the Big Island through tonight,
and remains in effect for the typically windy waters around the
Big Island and Maui County through Tuesday night. The SCA advisory
may need to be extended through Thursday. The high will weaken
and move eastward late Thursday and Friday, leading to a slight
decline in the trades.

Surf across most shores will be below seasonal average through
the week. Surf along east facing shores will remain choppy
through Thursday due to persistent trades locally and upstream of
the islands. A decrease in trade winds will cause east shore surf
to decline Friday. South facing shores will continue to decline
over the next few days. A small southwest pulse out of the Tasman
Sea could produce a slight rise in surf Friday. Aside from trade
wind wrap, surf along north facing shores will be minimal through
Wednesday, and a tiny northwest swell will be possible Thursday or
Friday.

The combination of seasonally high astronomical tides and water
levels running around 6 inches higher than predicted will produce
localized coastal inundation each afternoon through Tuesday. A
Coastal Flood Statement has been issued to highlight these
conditions.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Tuesday for Kaiwi Channel-
Maui County Windward Waters-Maui County Leeward Waters-Big
Island Windward Waters.

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

&&

$$

DISCUSSION...Jelsema
AVIATION...Farris
MARINE...Shigesato