Halawa, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

504
FXHW60 PHFO 200124
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
324 PM HST Sat Jul 19 2025

.SYNOPSIS...
A weak upper low northwest of Kauai and higher moisture pooling
over and north of the islands maintain higher shower intensity
and coverage statewide, with a chance for some heavier downpours
into Sunday, especially over windward higher terrain. Stable,
drier weather is expected to return early next week with more
typical scattered windward trade showers.

&&

.DISCUSSION...
The wetter pattern from last night has continued through the day
today, with the arrival of a slug of low level moisture. Many
sites recorded 0.3 to 1.5 inches over the past 12 hours, with a
few standout spots on upslope windward Maui and the higher Koolau
terrain on Oahu coming in with upwards of 2 to 3 inches. The
afternoon (00Z) soundings came in with precipitable water values
around 1.9 inches at Lihue and 1.7 inches at Hilo, up from the
1.47 inches measured at both early this morning. The Lihue
sounding continues to show a lack of low-level inversion in
response to the westward passing 700 mb trough axis, currently in
the vicinity of Kauai, and cooling initiated by an upper-level
trough/low system to the northwest. The Hilo sounding is now
showing a couple of weak inversions as stability begins to
increase over the eastern end of the state behind the lower-level
trough. Otherwise, surface high pressure far north-northeast of
the state will continue to drive moderate to locally breezy trade
winds over the islands for the next several days.

These low pressure features will tap into the increased moisture
pool to maintain enhanced showers into Sunday, with the highest
rainfall amounts focused along windward higher terrain. For tonight
into Sunday, the high-res model guidance depicts the area of highest
rainfall between 20 to 25 N (the western half of the state, though
windward areas of the other islands will still see enhanced showers
due to the higher available moisture. The forcing of the weak upper
low to the northwest will focus the better-organized convection over
the far north/northwestern offshore waters for the rest of today
into early next week, leaving the chances for thunderstorms over
the islands themselves pretty low. However, the upper levels should
cool enough to provide enough instability for a slight chance of
thunderstorms over the northern Kauai coastal waters this evening
into Sunday.

A stable summer-like trade wind pattern will return by late Monday
as lingering moisture advances west and drier air filters in behind
it. From Tuesday onward mid-upper level ridging will become reestablished
over the islands. A weak mid level shortwave trough may brush the
western end of the state Wednesday, briefly enhancing trade wind
showers across Kauai and Oahu. Model guidance does hint at a surface
trough approaching from the east toward the end of the coming week,
that could briefly disrupt the trade flow, weakening winds as they
back a touch more out of the northeast.

&&

.AVIATION...
High pressure far north of the islands will maintain moderate to
locally breezy trades through the weekend. Lingering instability
associated with a weak upper level disturbance north of Kauai and
a moist air mass across the state will result in periods of MVFR
showers across mainly windward and mauka areas through Sunday,
with some showers moving into leeward areas overnight. Isolated
thunderstorms are also possible across the waters north and east
of Kauai through late tonight.

AIRMET Sierra for mountain obscuration remains in effect for
windward sections of Kauai and Oahu. With little change expected
overnight.

&&

.MARINE...
Locally fresh trade winds will be in place through the forecast
period. A weak trough moving through the region and a trough far
north of the area will keep trade winds in the gentle to locally
fresh range this weekend. As the trough north of the area moves
west and weakens, high pressure will build and gradually strengthen
trade winds next week.

A mixed southerly/southwesterly swell will provide average surf
along south facing shores through Sunday. The small long period
southwest swell is expected to continue to fill in through the
afternoon, peak late tonight then decline slowly through early
next week. Another tiny to small southerly pulse is possible
later towards the end of next week.

Surf along east facing shores will gradually decline through the
weekend with the weakening trade winds. Surf along north facing
shores will remain nearly flat through the forecast period.

Peak high tides associated with the lunar cycle could lead to
minor coastal flooding along shorelines and low-lying coastal
areas next week Monday through Wednesday during the daily peak
tide each afternoon.

&&

.FIRE WEATHER...
Fire weather concerns will be low this weekend as a result a
wetter pattern with moderate to locally breezy trade winds the
next few days. Drier weather is expected to return early next
week, which could enhance fire weather concerns slightly, though
trade wind speeds will remain on the more moderate side.

&&

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

&&

$$

DISCUSSION/FIRE WEATHER...TS
AVIATION...Ahue
MARINE...Tsamous