935
FXHW60 PHFO 230120
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
320 PM HST Sun Sep 22 2024

.SYNOPSIS...
Moderate trade winds will prevail through Monday as the surface
ridge to the north briefly weakens. Rainfall will favor windward
and mauka locations, but a few showers, some heavy, may develop
across leeward areas as a disturbance aloft moves overhead.
Locally breezy trades and more stable conditions will return on
Tuesday and persist into next weekend.

&&

.DISCUSSION...
A surface ridge far north of the islands will drive moderate trade
winds through tomorrow, and instability produced by an upper-
level low will generate briefly heavy showers. The upper-level low
remains centered just north of Kauai and Oahu this afternoon and
will creep west slowly over the next couple of days. This feature
has weakened and elevated the inversion over most of the island
chain and is producing high lapse rates above 15,000 ft close to
the core of the low. However, with no organized areas of moisture
expected through Monday, an increase in widespread rainfall is
unlikely. As a result, expect the locally scattered showers
moving along the trades to be briefly heavy. Afternoon sea breezes
in sheltered areas will generate spotty showers, some heavy,
across leeward terrain, with some showers lingering into the
evening. So far, rainfall has not been significant, but there is
some potential for some minor flooding concerns over leeward Big
Island each afternoon and evening.

A stronger and more stable trade wind flow will develop on
Tuesday. The locally breezy trades will be driven by a tighter
pressure gradient between the strengthening low-level ridge to the
north and a pair of tropical disturbances passing several hundred
miles south of the islands. The upper-level low will fill and
drift away to the west, and a ridge aloft building in from the
east will bring stability. Through the rest of the work week,
expect typical windward rainfall for most islands, though windward
Big Island may be brushed with some deeper tropical moisture
Wednesday night through Thursday night.

&&

.AVIATION...
Moderate trades should continue through tomorrow. SHRA and low
cigs should mostly be confined to windward and mauka locations.
MVFR conds can be expected in SHRA, but otherwise VFR should
prevail.

No AIRMETs are in effect.

&&

.MARINE...
Fresh trades ease slightly into Monday as the ridge north of the
islands weakens. Locally strong trades then develop Monday night
and persist for the remainder of the week. A Small Craft Advisory
for the windier waters of Maui County and the Big Island will
likely be needed by Tuesday or Tuesday night.

Surf along north and west facing shores will remain tiny through
Monday. A moderate, long-period NW swell will arrive on Tuesday
and push surf heights along north and west facing shores well
above the seasonal average Tuesday night and Wednesday but will
fall short of the High Surf Advisory threshold.

Surf along south facing shores will remain just below seasonal
average levels as a SW swell advances through area waters. A
reinforcing SW swell is expected late Monday into midweek. East
shore surf remains small in response to declining trades with an
upward trend anticipated beginning Monday night as trades
restrengthen.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Wroe
AVIATION...Walsh
MARINE...JVC