Heavy Rain in Hawaii, August 6, 2022

Area Forecast Discussion
National Weather Service Honolulu HI
326 AM HST Sat Aug 6 2022

.SYNOPSIS...
Southeast wind will focus clouds and showers over southeast-
facing slopes of Maui County and the Big Island while afternoon
sea breezes bring interior clouds and showers to the western end
of the state. Trades return to the entire state tonight into early
Sunday.

&&

.DISCUSSION...

Trades will make a gradual return during the next 18 to 24 hours
as the surface trough near Kauai exits stage west concurrent with
the southern periphery of the northeast Pacific high pressure
building toward the islands. For Kauai and Oahu, continued light
winds during the day will once again give way to localized sea
breezes, interior cloud development, and a few showers. Reductions
to mid-level stability will occur as the resident batch of
moisture centered south of the islands works through the area
today. This, combined with an uptick in boundary layer moisture
will offer potential for a slightly greater convective response
compared to yesterday. Over the eastern end of the state, building
ESE winds will deliver occasional clouds and showers to favored
east and southeast-facing slopes.

As trades become established early next week, the diffuse nature of
the pressure gradient suggested by recent modeling puts the
islands in a somewhat precarious position in terms of forecast
confidence for the strength of said trade winds. While breezy
trades are indicated through much of next week, the tightening of
the local gradient appears to be more closely tied to pressure
falls in the tropics south and southeast of the islands which
inherently carries comparatively greater uncertainty. In either
case, some semblance of easterly trades will develop on Sunday and
persist through most or all of next week bringing a return to a
more typical trade wind pattern. As noted in the previous
discussion, any additional pressure falls south of the area such
as those related to tropical development would have the potential
to give local winds another upward nudge during mid-week.

&&

.AVIATION...

Land breezes have pushed much of the clouds and showers offshore
overnight over the smaller islands. Trade wind flow will become
reestablished over windward Big Island this morning and spread
across the remainder of the state through tonight. Leeward areas
over the western end of the state may still experience localized
sea breezes and inland clouds/showers this afternoon as the trades
slowly return. A few bands of showery low clouds will continue to
move into east and southeastern portions of the Big Island and
Maui this morning, before dissipating by the afternoon. Shower
activity will return to a more typical windward and mauka focus
tonight.

&&

.MARINE...

A surface trough N of the area will gradually drift northward and
weaken over the next few days, allowing surface high pressure to
the distant N to re-exert its influence on our winds. As a result,
E to SE winds will increase from E to W across the island chain.
Winds will remain on the lighter side over Kauai and Oahu today,
but are expected to increase over Maui and Big Island waters, and
a Small Craft Advisory (SCA) has been issued in anticipation that
winds will increase. Winds will likely continue to gradually
increase into the middle of next week as the high moves closer,
and a potential tropical disturbance passes far S of the islands.

Little significant swell is anticipated through next week. A small
short-period NE swell will continue today and diminish tomorrow.
The increasing trade winds bringing a gradual increase in short-
period waves to E shores early next week. A small, long-period S
swell may arrive around the middle of next week, with a small,
shorter-period SSE swell expected over the next couple of days.

&&

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

Small Craft Advisory until 6 AM HST Sunday for Maui County
Windward Waters-Big Island Windward Waters.

&&

DISCUSSION...JVC
AVIATION...TS
MARINE...Birchard