Mililani Town, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

322
FXHW60 PHFO 210647
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
847 PM HST Wed Nov 20 2024

.SYNOPSIS...
Gradually diminishing trade winds will deliver just a few showers
to windward areas of the smaller islands for the next day or so,
while windward Big Island will continue to receive passing
showers. Light and variable winds and mostly dry weather are
expected statewide from Thursday night into Sunday. A weak front
may move over the islands from the northwest late this weekend.
This front is expected to bring little in the way of rainfall,
however, and winds will remain fairly light.

&&

.DISCUSSION...
This evening, weakening high pressure remains centered about 400
miles north of Honolulu, which is promoting moderate trade winds
over the islands. Dry air and stable conditions are prevailing
over most of the state. CIMSS MIMIC Layer Precipitable Water (PW)
imagery shows values between roughly 0.75 and 0.95 inches over
the smaller islands, which agrees with the afternoon 00z sounding
from Lihue which showed stable conditions, an inversion near 5000
feet, and PW at 0.80 inches. Satellite and radar imagery also
shows minimal shower activity over much of the state this evening.
The exception is for windward Big Island, where a deeper mixed-
layer is located and lingering moisture upstream continues to
move in on the moderate trade winds. For the rest of tonight,
little change in the overall regime is expected with only a few
isolated light showers for windward sections of the smaller
islands and greater coverage over windward Big Island.

Gradually diminishing trade winds will deliver little in the way of
rainfall to windward areas of the smaller islands the next day or
so, while windward Big Island will continue to receive passing
showers. Shower coverage and frequency over windward Big Island should
taper off by Thursday night as a land and sea breeze wind pattern
develops statewide. This will occur as the high pressure north of
the state moves south and dissipates, leaving a surface ridge
near/over the islands. This light wind and mostly dry regime will
persist into at least Sunday, after which forecast details become
increasingly uncertain.

Late Sunday into Monday, a weak front is expected to approach
from the northwest, and deterministic model guidance continues to
offer inconsistent solutions for the prognosis of this feature
and the evolution of the weather pattern early next week. Ensemble
guidance, however, indicates that we can be confident that winds
remain light and precipitation totals associated with the
potential frontal passage will remain fairly low. A relatively dry
post-frontal weather pattern should persist well into next week
as we head into the Thanksgiving holiday.

&&

.AVIATION...
Trades will decrease gradually through Friday. Expect showery
weather for windward Big Island through tonight, with periods of
MVFR conditions. Some of the heavier showers may produce brief
IFR conditions. Elsewhere, expect fair trade wind weather with a
few light showers possible over windward and mauka areas.

No AIRMETs are currently in effect. As showers increase over
windward Big Island this evening, AIRMET SIERRA may be needed due
to mountain obscurations.

&&

.MARINE...
Weakening surface high pressure settling in over the far north
offshore waters will maintain primarily gentle to locally moderate
breezes through late week. A west-to-east orientated surface
ridge axis of high pressure laying across the northern coastal
waters will result in generally light to gentle breezes, with
slightly stronger winds in the Alenuihaha Channel and south of Big
Island, the next several days. Light winds are favored ahead of
the approach of a weak front nearing Kauai Sunday. This shallow
frontal passage will disrupt trade flow as early week gentle
easterly breezes veer northwest then northeast.

No significant swells are expected the next couple of days as
trade wind waves slowly subside leading to a more calm sea state.
Nearshore windward buoys are observing a 4 to 5 foot trade wind
swell that will further decline throughout the remainder of the
week as a result of light trades.

A series of northwest and north-northeast swells are due later
this week. A tiny 1 to 2 foot, 15 second period northwest (320
degree) swell is being observed at the nearshore CDIP buoys as it
moves around the islands this evening. This swell will level out
around 2 feet tonight and then hang in through Friday. A larger
3 to 6 foot northwest (310-320 degree) medium period swell
developing from a pair of lows far northwest of the islands is
scheduled to travel through this weekend and peak Sunday. A
smaller reinforcing northwest pulse (320 degree) is due Monday and
Tuesday.

A small, short to medium period north (010-020 degree) swell will
slowly build in tonight and Thursday and then hold at 4 to 5 feet
Friday and Saturday. A very large, powerful hurricane force low
churning off the U.S. Pacific Northwest coast will send an
overlapping north-northeast (010-030 degree) swell across the
islands late Thursday night, peaking Sunday into Monday and then
fading on Tuesday.

While none of these swells are expected to produce advisory level
surf, the potential for high surf along north and east-facing
shores will need to be monitored, especially as the combining
north northeast swells peak early in the week.

&&

.FIRE WEATHER...
KBDI values remain high across the state and an overall dry
weather pattern is expected for the next several days. With this
dry air moving overhead, relative humidity values will have the
potential to reach the critical 45% threshold from late morning
through the afternoon each day through Sunday. Fortunately,
however, weak trade winds will mitigate fire weather concerns
through the rest of this week.

&&

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

&&

$$

DISCUSSION...Vaughan
AVIATION...Powell
MARINE...Blood
FIRE WEATHER...Vaughan