465
FXHW60 PHFO 161935
AFDHFO

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

.SYNOPSIS...
Locally breezy trade winds will continue to bring humid and
somewhat wet conditions, especially for windward areas, into
tonight. Drier trade wind weather will prevail Tuesday into the
weekend, with moderate showers focused over windward slopes.

&&

.DISCUSSION...
An area of moisture accompanying a mid-level trough produced
active rainfall overnight. Every island has a windward station
that registered over 1 inch of rain during the past 12 hours, and
windward and southeast Big Island and northern portions of
windward Oahu received widespread rainfall of 3 to 6 inches
during this time.

Locally breezy, somewhat wet, and humid conditions will prevail
into tonight, though a decrease in rainfall intensity is
expected. The mid-level trough is creeping westward, which will
ensure precipitable water remains in excess of 1.5 inches over
much of the state into at least the evening. Drier air in the
easterly trade wind flow will slowly spread westward during this
time, decreasing the fuel for the high rainfall amounts that were
experienced last night. Therefore, expect showers to remain
largely confined to windward slopes, where another 1 to 2 inches
may fall. Afternoon convection with spotty heavy showers will
likely form along leeward Big Island and leeward Haleakala on
Maui, and even though a ridge aloft will cap the convection, a
brief thunderstorm cannot be ruled out on the upper slopes of the
Big Island. With dew points hovering in the low to mid 70s,
expect humidity to remain elevated.

The deeper moisture will move off to the west on Tuesday,
bringing a less active shower pattern. Surface high pressure
north of the state will drive moderate to locally breezy trade
winds, with a brief decline in the trades possible around Thursday
and Friday. While a ridge aloft will bring stability, the mid-
level trough will linger nearby into Wednesday, which will keep
shower chances a bit higher than normal. However, dew points will
fall into the upper 60s over most leeward areas, bringing some
relief from the humidity. Drier conditions are due Thursday and
Friday and likely into the weekend.

&&

.AVIATION...
For the windward terminals MVFR conditions, and isolated IFR, are
expected in heavier showers through this morning. Elsewhere and
otherwise, 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 all
islands.  These conditions will persist through the morning and
will likely 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 continue through
Wednesday as strong surface high pressure remains to the north
northeast of the islands. Winds are then expected to decrease
slightly to moderate levels after Wednesday as the surface high
pressure slightly weakens and moves east. A Small Craft Advisory
(SCA) is in effect for all waters surrounding Maui County and the
Big Island through tonight, and then the typically windy waters
around the Big Island and Maui County through Tuesday night. The
SCA may need to be extended through Wednesday.

Surf across most shores will be below seasonal average through
the week. Surf along east facing shores will remain choppy
through Wednesday due to persistent trades locally and upstream of
the islands. A decrease in trade winds will cause east shore surf
to decline Thursday and 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. Then a slightly larger northwest swell
will be possible by late Monday next week.

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...Wroe
AVIATION...Brenchley
MARINE...JVC/Tsamous