Halawa, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

402
FXHW60 PHFO 210152
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
352 PM HST Fri Sep 20 2024

.SYNOPSIS...

A moderate to locally breezy trade wind pattern will continue
through tonight. Enhanced windward showers are expected this
weekend as a weak disturbance moves through the region. A drier
and more stable trade wind pattern will return early next week.

&&

.DISCUSSION...

Satellite and radar imagery show low clouds and isolated showers
moving into windward areas on the moderate to locally breezy
trades this afternoon, with an occasional shower or two making it
into leeward areas at times. Low clouds and showers are also
building up over some leeward areas across the Big Island, Maui
and Oahu where sea breezes have developed. Temperature inversion
heights were measured around 9000 feet at Lihue around 2 PM this
afternoon and are allowing showers to deliver brief moderate
downpours to these areas. In addition, patches of high clouds can
also be seen moving across the region from the west with little
to no impact on the sensible weather...but might make for a
beautiful sunset this evening.

A shift in the pattern is expected for this this weekend. An
upper level low will dip down over the state from the north
Saturday night into Sunday, and a weak low level trough will move
in from the east on the trades. With modest forcing in both the
low to mid levels and pockets of low level moisture embedded in
the trades, trade wind showers will likely be enhanced through
the weekend, especially Saturday night into Sunday. Forecast
soundings show temperature inversion heights lifting to at least
12,000 ft Saturday night/Sunday morning for locations across the
northern half of the state, which will allow for greater vertical
development in showers and potentially heavier rainfall rates.
However, model QPF amounts are not reflecting any significant
rainfall totals at this time.

In addition, cooler temperatures aloft will move overhead with
the mid to upper level low, allowing instability to increase...which
raises the question of whether or not we`ll see any thunderstorms
this weekend. With only marginal instability, small pockets of
enhanced low level moisture, and weak surface forcing, decided to
hold to the previous forecast philosophy and keep any mention of
thunder out of the gridded forecast through the weekend.

A drier and more stable moderate trade wind pattern will return
early next week as the upper level low and low level trough both
move west of the state. Pockets of moisture will bring periods of
overnight to early morning showers to mainly windward and mountain
areas.

&&

.AVIATION...
Pockets of moisture moving along the moderate to locally breezy
trade flow will generate periods of MVFR conditions along
windward slopes, mainly at night and in the morning. VFR will
prevail over leeward areas. No AIRMETs are in effect, though we
will monitor for windward mountain obscuration tonight. An upper-
level low will move over the state during the weekend and could
bring a more active shower pattern with higher chances for MVFR
conditions over windward areas by Saturday night.

Trade winds appear to be slightly too weak to produce significant
low-level turbulence. However, low-level wind shear has been
reported around Kahului, and conditions will remain conducive
through late afternoon.

&&

.MARINE...
Fresh to strong easterly trade winds will continue through
Saturday, then ease into the gentle to moderate range Sunday
through Monday as a weak trough passes north of the state. A
Small Craft Advisory (SCA) remains in effect for the windier
waters around Maui County and the Big Island through Saturday.
Fresh trade winds should return by Tuesday of next week and the
trades may approach SCA thresholds for our typical windier waters
around Maui County and the Big Island once again.

Surf along north facing shores will trend up through the first
week of fall, beginning next Tuesday in response to a gale
developing near the Kurils today, racing eastward across the Date
Line near the Aleutians this weekend, then to the Gulf of Alaska
early next week. Guidance shows this northwest swell peaking
locally Tuesday night into Wednesday out of the northwest, then
fading Thursday into Friday as it shifts out of a more north-
northwest direction.

Surf along east facing shores will remain small and choppy into
Saturday, then decrease Sunday into next week as the trades lower
locally and upstream across the eastern Pacific.

Surf along south facing shores will remain small through the
weekend, with mainly a mix of background long-period southwest and
short-period southeast swells moving through. An upward trend is
possible Tuesday through midweek due to a slightly larger
southwest swell arriving.

&&

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

&&

$$

DISCUSSION...Farris
AVIATION...Wroe
MARINE...Kino