532
FXHW60 PHFO 230129
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
329 PM HST Sat Feb 22 2025

.SYNOPSIS...
Light east to southeast winds and mostly dry conditions will
prevail through early next week, with a few showers possible along
windward slopes and coasts at night and over the island interiors
each afternoon. A series of cold fronts will approach from the
northwest next week, bringing an increase in showers, particularly
over the western end of the state for the latter half of the work
week.

&&

.DISCUSSION...
This afternoon`s radar and satellite imagery show a few clouds
and isolated showers moving into windward areas of the eastern end
of the state on the light to moderate east-southeasterly trades.
Over the western half, the low level clouds and isolated showers
slow and take on a more southeasterly direction as a weak cold
front approaches from the northwest and relegates the island chain
to the southwestern periphery of a surface ridge. In addition,
sea breezes have developed across most of the state, increasing
clouds over leeward and interior areas and bringing the
occasional light shower.

With a progressive pattern to our north, a series of three fronts
will approach the state from the northwest over the next week,
but will likely dissipate just north of the area or only briefly
brush Kauai. The first will near today into tomorrow, the second
on Tuesday, and the third on Thursday into Friday...with each
front seeming to nudge slightly closer to the state. As each front
nears, the local pressure gradient will relax, bringing light
background winds that will allow for land and sea breezes to
become more prevalent. The surface ridge centered to the far
northeast will try to reestablish itself after each front passes
to our north, but the quick succession of fronts will only allow
trades to return briefly to the area before the local pressure
gradient weakens yet again and land and sea breezes dominate.

The fluctuations in the prevailing wind speed and direction will
determine where any showers are likely to develop each day. With
the lighter wind days expected today, Tuesday and Thursday as each
front nears, a land and sea breeze pattern featuring windward
showers at night and interior showers during the day will
dominate...with a slight uptick in showers over the western end of
the state possible. On Sunday into Monday, moderate easterly
trades will try to build back in, with clouds and showers favoring
windward and mauka areas, particularly overnight, although
isolated sea breeze showers will be possible in the afternoon.
On Wednesday, winds will turn southerly and increase boundary
layer moisture which should cause inversion heights to rise,
bringing an increase in showers to mainly leeward areas,
particularly over the western end of the state. On Friday into
Saturday, moderate east- southeasterly trades should return, with
showers favoring windward and mauka areas over the eastern end of
the state and sea breezes bringing showers to island interiors of
the western half of the state.

With all of this said, mostly dry and stable conditions are
expected to persist through Tuesday due to limited available
moisture and increasing stability as mid-level ridging builds in
from the west. So any showers that move in on the trades or
develop across inland areas with the sea breeze should be brief
and light. With the southerly flow on Wednesday into Thursday,
low level moisture will increase and 500 mb heights are expected
to gradually fall into the weekend, allowing for a slightly more
active shower pattern ahead of and near the frontal boundary as it
approaches on Thursday into Friday.

&&

.AVIATION...
A ridge just north of the islands will bring light and variable
winds statewide through tonight. Sea breezes resulted in interior
cloud build ups and mountain obscurations this afternoon and will
likely linger until around sunset. AIRMET Sierra is posted for
tempo mountain obscurations above 2500 feet for Kauai, Oahu and
Molokai through 04Z today. VFR conditions will prevail across
the rest of the state. Land breezes will clear out skies tonight,
followed by the return of light trade winds Sunday.

&&

.MARINE...
High pressure remains over the northeastern Pacific, with a ridge
extending southwest over the islands. The ridge will keep light
and variable winds in place for the western end of the state, and
light to moderate southeasterly winds for the eastern part of the
state through tonight. Light to moderate easterly trade wind flow
will return Sunday into Monday as high pressure briefly rebuilds
north of the state. A front is forecast to pass just north of the
islands on Monday, weakening wind speeds over the islands again
into Tuesday. A very short period of east to east-southeast trades
returns for Tuesday afternoon into Wednesday, before quickly shifting
out of the south Wednesday afternoon ahead of a front approaching
from the northwest.

The current west-northwest swell will hold through this evening
before a long-period reinforcement builds in tonight through Sunday.
Surf heights are expected to reach advisory levels after midnight
tonight and peak Sunday afternoon along north and west facing shores.
A High Surf Advisory (HSA) has been issued for north and west facing
shores of Niihau, Kauai, Oahu, Molokai and north facing shores of
Maui through Sunday night. If this swell comes in larger than expected,
may need to add west facing shores of the Big Island to the HSA, as
well as issue a Small Craft Advisory for hazardous seas of 10+ feet.
This swell will slowly lower through the first part of next week.
A slightly larger northwest swell is expected to build in late Tuesday
and linger through Wednesday, resulting in peak surf heights near-
warning level for north and west facing shores. Small surf is expected
along south and east facing shores.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory from midnight tonight to 6 AM HST Monday for
Niihau-Kauai Leeward-Waianae Coast-Oahu North Shore-Maui
Windward West-Kauai North-Molokai Windward-Molokai North-Molokai
West-Maui Central Valley North-Windward Haleakala.

&&

$$


DISCUSSION...Farris
AVIATION...Foster
MARINE...TS