919
FXHW60 PHFO 010131
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
331 PM HST Mon Jun 30 2025

.SYNOPSIS...
Light east to east-southeast trade winds with localized land and sea
breezes are expected today and tomorrow as a weak surface trough
lingers north of the islands. High pressure will build north of the
area by Wednesday, backing and increasing trade winds into the
moderate to breezy range through the rest of the week. Passing
showers are expected for typical windward and mountain areas,
with some additional showers over the leeward areas during
afternoon cloud buildups today and possibly tomorrow. Trade winds
could become moderate to strong by the weekend as high pressure
is forecast to build further.


&&

.DISCUSSION...
A surface trough to the north of the islands has weakened the
pressure gradient, which has allowed trade wind speeds to be light
to moderate and blow out of a east-southeast direction. Localized
land and seas breezes are possible today and tomorrow especially for
sheltered leeward areas. This trough is expected to weaken and
eventually dissipate around the middle of the week. This will result
in trade winds backing to an easterly direction and gradually
increasing into the moderate to breezy range.

A typical shower distribution can be expected through the week with
passing showers moving over windward and mountain areas, some
additional cloud and shower buildups are expected for leeward areas
this afternoon and to a lesser extent tomorrow afternoon as winds
remain light. Drier conditions are possible tomorrow as a pocket
of drier air moves through, followed by periodic plumes of
moisture and dry air through Friday.

Conditions look to dry out further by the weekend and into next week
as high pressure becomes firmly established to the northeast and
brings a dry and stable airmass to our region. Concurrently, global
models indicate trade winds becoming breezy to strong. These factors
could elevate fire weather concerns as shower activity could also
be limited.


&&

.AVIATION...

Moderate east-southeast trades will prevail through this evening.
The lighter east-southeasterly flow has allowed sea breezes to
develop across some leeward and interior areas this afternoon.
These sea breeze showers will clear out later this evening, then
clouds and showers will favor windward and mountain areas
overnight as pockets of moisture ride in on the trades. As a
diffuse surface trough exits the region to the west, the trades
will strengthen slightly and gradually back out of the east
tomorrow. Some leeward and interior sea breeze clouds and showers
will be possible again, but will likely be less active than
today. Brief periods of MVFR conditions will be possible in any
showers, but overall VFR conditions should prevail.

AIRMET Sierra is in effect for mountain obscuration across leeward
and interior Oahu where sea breeze showers have been most active.
This AIRMET will likely be cancelled later this evening.


&&

.MARINE...

A trough positioned north of the islands causes trades to veer
slightly to ESE and weaken to moderate this week. Fresh to
locally strong trades return this weekend as high pressure
reestablishes north of the islands.

Small, long period S swell filling in today will hold through
tomorrow with surf peaking near the summertime average for S
shores. A smaller long period S swell then advances through area
waters toward the end of this week bringing a slight boost to
surf. Surf along E shores matches trade wind trends, subsiding and
remaining small this week then increasing this weekend. Surf along
N shores remains seasonally tiny through the period.



&&

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

&&

$$


DISCUSSION...Tsamous
AVIATION...Farris
MARINE...JVC