Ewa Gentry, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

186
FXHW60 PHFO 201340
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
340 AM HST Sat Dec 20 2025

.SYNOPSIS...
Lingering instability over the islands continues to produce
showers and isolated thunderstorms over the smaller islands. Light
southerly winds today will result in some afternoon sea breezes
that could produce additional showers and thunderstorms over
interior portions of the islands. Trade winds are expected to
slowly make a return tonight, and strengthen into the first part
of the new week.

&&

.DISCUSSION...
The main change with the morning forecast package was to add
thunderstorms over the smaller islands and surrounding waters for
today and tonight. Lingering instability from the stationary
front and trough to the north of the main Hawaiian islands will be
eroded by upper level high pressure to the southeast of the
islands moving over the islands tonight. Light winds over the
islands today will lead to afternoon sea breezes that will likely
help contribute to afternoon convection over the smaller islands.

The threat for widespread flooding remains low, but with saturated
grounds over the islands, particularly on Kauai and Oahu,
additional showers could prompt additional flood advisories at
times.

As the surface boundary is eroded, high pressure far north of the
islands will sink southward bringing trade winds back to the
region as early as late tonight. Trade winds will then strengthen
to moderate to locally breezy levels by Monday or Tuesday. The
trades will carry in residual moisture from the surface boundary
to the windward and mauka areas. The GFS and ECMWF are in good
agreement with an mid-level high pressure ridge remaining over
the islands through the end of the week.


&&

.AVIATION...
An unstable atmosphere remains in place over the islands with
light southerly flow. Clouds and showers continue to move over the
smaller islands, bringing occasional MVFR conditions, and isolated
IFR conditions. Thunderstorms will also continue to be a
possibility that could produce gusty conditions and briefly heavy
rain. The Big Island is expected to have primarily VFR
conditions, but the occasional shower moving overhead could bring
brief MVFR conditions.

Wind may be light enough to day for afternoon sea breezes that
could help to initiate some afternoon convection over the islands.
Trades are expected to return late today.

AIRMET Sierra for mountain obscuration is in effect for Lanai,
Kahoolawe and Maui. This may need to be expanded to additional
areas at times.


&&

.MARINE...
A lingering unstable airmass will lead to another round of
scattered showers and isolated thunderstorms today over the
western coastal waters with light and variable flow. Gentle to
locally moderate southeasterly winds will prevail across the
eastern waters with less shower activity. By late this weekend,
easterly trade winds will gradually strengthen with the potential
for SCA conditions over the windier waters and channels around
Maui County and the Big Island. Expect trades to become even
stronger early to mid next week as surface high pressure builds to
the north.

Two overlapping small to moderate, medium period, northerly
swells (350 deg) and (010 deg) will dominate through the remainder
of this weekend and bring elevated surf to north facing beaches.
However, surf should stay just shy of High Surf Advisory criteria
and combined seas will remain below Small Craft Advisory criteria.
Late Sunday through mid next week, north swell energy fades which
should allow surf to drop to below seasonal averages.

Surf along east facing shores will remain small through tonight
given the lack of trade winds upstream of the islands, but areas
exposed to the north swell will see an uptick. As trade winds
gradually strengthen late Sunday through early next week, east
facing shores could become rough and choppy. Surf along south
facing shores will remain flat to tiny through the weekend into
early next week.

&&

.FIRE WEATHER...
Conditions are expected to remain below critical fire thresholds
over the next several days. Showers and generally high relative
humidities will be accompanied by light southerly winds today that
will transition to trade winds over the next couple of days.


&&

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

&&

$$


DISCUSSION...M Ballard
AVIATION...M Ballard
MARINE...Thomas
FIRE WEATHER...M Ballard