670
FXHW60 PHFO 150645
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
845 PM HST Tue Jan 14 2025

.SYNOPSIS...
Moderate to locally breezy trades will gradually weaken Wednesday
and Wednesday night. Trade showers are expected to diminish
overall as well, though some showers could linger for windward Big
Island and Maui into Wednesday night. A relatively weak and
disorganized cold front will push down the chain Thursday night
through Saturday. Unstable air associated with the front should
enhance showers during this period, with a small chance for a
couple rumbles of thunder in a few spots as well. More stable and
dry air should gradually fill in behind the front on a rather
cool northerly flow, which will eventually turn to trades over the
holiday weekend.

&&

.DISCUSSION...
Currently at the surface, a 1029 mb high is centered around 1100
miles north of Honolulu. A stationary front is located around 250
miles north of Kauai and a cold front is positioned around 1050
miles west-northwest of the Garden Isle. The resulting gradient is
producing moderate to locally breezy trade winds across the
island chain this evening. Infrared satellite imagery shows partly
to mostly cloudy conditions across the state, with cloud cover
most prevalent in windward areas as well as leeward sections of
the Big Island. Main short term focus revolve around trade wind
trends and rain chances.

Moderate to locally breezy trades will prevail tonight, then ease
up Wednesday through Thursday as a front approaches from the
northwest. The winds will become light enough to allow land and
sea breezes to dominate late Wednesday night and Thursday. A cold
front will then slide southeastward down the island chain
Thursday night through Saturday. Light to moderate west to
southwest winds will develop in advance of the front, while
moderate northwest to north winds fill in behind it. The front
should have cleared the Big Island by Saturday evening, with
moderate to locally breezy northeasterly trades expected Saturday
night through Sunday night as high pressure builds eastward to the
north of the state. The trades will then ease up again early next
week as the next front approaches the island chain from the
northwest.

As for the remaining weather details, fairly typical trade wind
weather will prevail tonight and early Wednesday with showers
favoring windward slopes and coasts. Mid-level ridging will build
over the islands reduce shower coverage considerably Wednesday
afternoon and Wednesday night. The exception may be over windward
sections of Maui and the Big Island where an area of enhanced
moisture appears to move in from the east bringing an increase in
shower activity Wednesday night. Fairly dry and stable weather
will continue on Thursday, with morning showers favoring windward
sections of Maui and the Big Island, with a few daytime heating
showers developing over the interior of the islands in the
afternoon. There remains some uncertainty regarding the timing and
strength of the late week cold front, but overall we should see
an increase in showers in association with the front as it
progresses southeastward down the island chain Thursday night
through Saturday. There is a slight chance for thunderstorms over
the higher terrain of Maui and the Big Island Friday afternoon,
which could bring some wintry precip to the summits of Mauna Loa
and Mauna Kea if they occur. Behind the front drier and more
stable conditions will build in. Fairly dry and stable conditions
should then prevail Saturday night through early next week, with
showers limited primarily to windward slopes and coasts.

&&

.AVIATION...
Moderate trades slightly weakening as a cold front approaches
from the northwest. Low cigs and SHRA should be focused over
windward and mauka areas. However, localized sea breezes will be
possible tomorrow and may bring clouds and isolated showers to the
most wind-protected leeward areas as well. Brief MVFR conds can
be expected in SHRA but otherwise, VFR should prevail.

No AIRMETs are in effect.

&&

.MARINE...
A cold front and low pressure system passing just north of the
island chain will weaken the trade winds through Wednesday. A
light wind regime with expanding near shore land and sea breezes
are expected from Thursday through the end of the week. The cold
front will move into the northwestern Hawaiian Islands from
Thursday night into Friday supported by an upper level trough.
Expect numerous showers with this next system, including the
potential for thunderstorms during this time period.

The current long period northwest swell will continue to decline
through Wednesday. The forerunners of the next significant
northwest swell will move into the islands by Thursday night, and
then swiftly build above warning thresholds along exposed north
and west facing shores from late Friday into Saturday, then
falling to advisory thresholds Sunday. Another medium period
northwest swell is forecast to fill in from Tuesday to Wednesday
of next week, keeping surf heights for next week elevated along
north and west facing shores.

Surf along south facing shores will remain very small through
Wednesday afternoon. A small long period south swell boost will
develop from Wednesday night into Thursday, peaking by Friday,
and slowly easing through the weekend. PacIOOS buoy observations
located in American Samoa are running above model guidance,
suggesting surf may peak just below High Surf Advisory levels.

Surf along east facing shores will slowly decline through the end
of the week. A small north swell could potentially elevate surf
along exposed shorelines on Wednesday and Thursday.

&&

.FIRE WEATHER...
No critical fire conditions anticipated during the forecast
period, although we will keep an eye on Sunday which could feature
the lowest post-frontal relative humidities and a relative peak
in N or NE winds. For now, both wind speeds and RH are not expected
to reach Red Flag Warning criteria, but guidance suggests it may
be close.

&&

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

&&

$$

DISCUSSION...Jelsema
AVIATION...Walsh
MARINE...Bohlin
FIRE WEATHER...Jelsema