459
FXHW60 PHFO 091318
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
318 AM HST Tue Jul 9 2024

.SYNOPSIS...
Moderate trade winds will steadily increase later today through
the rest of the week as a weak trough near Kauai moves away and
the surface ridge strengthens to the north. Showers will favor
windward and mauka locations, particularly through the overnight
and early morning hours as areas of moisture move through.
Although dry conditions will persist over our leeward areas, an
occasional brief shower may hold together.

&&

.DISCUSSION...
Guidance remains in decent agreement and shows a return of strong
and gusty trades beginning later today into Wednesday, in the
wake of a weak surface trough moving through the western end of
the state this morning. A decent-sized area of moisture and low
clouds (precipitable water values up around 1.4 inches)
accompanying this trough supports scattered showers, mostly over
windward and mauka locations. Accumulations from these showers
should remain light, with only a few brief showers reaching our
dry leeward areas. Drier air has already begun to reach the Big
Island this morning and will continue spreading westward as the
trough moves away from the area today.

A weak mid- to upper-level trough approaching on Wednesday will
move through from east to west late Wednesday night through early
Friday. This, combined with the gusty trades, could lead to
another period of enhanced windward and mauka shower coverage. For
the extended period, the surface ridge will remain strong to the
north, which supports the gusty trades holding through early next
week.

&&

.AVIATION...
Locally breezy trade winds will strengthen to moderate to strong
by this evening. AIRMET Tango for lee side turbulence will be
needed later today.

Bands of showers off the Pacific passing over the islands will
impact mainly the western half of of the state this morning. Drier
conditions expected in the afternoon and evening, but showery
weather should return to windward slopes and coasts early
Wednesday.

&&

.MARINE...
The Pailolo Channel and Maui windward waters were added to the
Small Craft Advisory (SCA) this morning due to the latest high
resolution model data. Otherwise, little change to the forecast.

A broad ridge remains north of the state and is expected to
strengthen over the next several days. Expect winds to increase to
moderate to locally strong levels over the next couple of days,
and then remain elevated into the weekend. The SCA is in effect
for the typical windier areas around Maui and the Big Island,
along with the Pailolo Channel and Maui windward waters.
Additional areas may need to be added Wednesday as the ridge
continues to strengthen.

The current small south-southeast swell will slowly decline this
week, while a small, long period south-southwest swell fills in
early Tuesday. This will maintain small surf along the south
facing shores for much of the week. A storm-force low pressure
system southeast of New Zealand will send a decent run of south
swells beginning this weekend. Resultant surf heights may reach
advisory thresholds of 10 feet along south facing shores during
its peak Sunday into Monday. Rough, choppy surf along east facing
shores will steadily increase during the middle to second half of
the week in response to the building trade winds upstream of the
state. Surf along north and west facing shores will remain nearly
flat.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 AM HST Wednesday for Big Island Summits.

Small Craft Advisory until 6 AM HST Thursday for Kaiwi Channel-
Maui County Windward Waters-Maalaea Bay-Pailolo Channel-
Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters.

&&
$$

DISCUSSION...Gibbs
AVIATION...Bedal
MARINE...M Ballard