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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 251349

Area Forecast Discussion
National Weather Service Honolulu HI
349 AM HST Sun Feb 25 2024

High pressure to the north of the main Hawaiian Islands will
continue to drive locally windy trade winds through much of the
week. Clouds and showers will favor windward and mauka areas, with
stronger winds helping to carry some showers to leeward areas.


Strong high pressure far north of the main Hawaiian Islands
continues to drive breezy to windy conditions across local waters
this morning. Windy trades are expected for the next several days
and a Wind Advisory remains in effect for portions of Maui County
and the Big Island. The areas most likely to see advisory level
winds include the Kohala Mountains on the Big Island, the central
valley of Maui and over ridges and through gaps on Molokai, Lanai
and Kahoolawe. Models suggest that advisory level winds could
occur on Oahu, but confidence is too low to include that island
in the Wind Advisory at this time. Nevertheless, winds will be
quite breezy there.

Satellite loop shows bands of broken low clouds riding in on the
trades, with radar confirming isolated to scattered moderate
showers beneath this cloud cover. These bands continue at
intervals far to the east of the islands, so expect increased
windward showers over the next day or so as each band passes by.
Stronger trade winds will push some of these showers across
leeward areas from time to time. A subtropical jetstream, marked
by the persistent pall of middle and high clouds, remains over the
islands and may enhance showers due to improved venting aloft.

By late next week, models show an upper trough moving over the
islands from the northwest, introducing a pool of destabilizing
cold air aloft. At the surface, high pressure will remain north of
the state and trade winds will persist at the surface. However,
associated trade showers may be heavier and more widespread as the
upper trough moves in.


Breezy to locally windy easterly trade winds will remain in place
over the next several days and will focus showers primarily over
windward and mountain areas. Latest satellite imagery early this
morning shows bands of broken low clouds upstream of the islands
that are moving westward towards the state. These bands will
maintain increased windward showers over the next 24 hours or so.
While VFR flight conditions will prevail for the most part,
occasional MVFR is expected as these bands move through.

AIRMET Tango remains in effect for moderate low-level turbulence,
and this AIRMET will likely be needed throughout the next several
days. AIRMET Sierra may be needed later this morning for mountain
obscuration across north through east facing slopes and coasts as
low clouds move through.


An area of large high pressure centered approximately 1,100
nautical miles north of the islands is producing a tight enough
pressure gradient back toward the state to sustain fresh to
locally strong trade winds. Little overall change in the Central
Pacific weather pattern will occur in the coming days as the high
remains anchored north of the area and maintains these winds for
several days. A Small Craft Advisory (SCA) remains in effect
for all Hawaiian nearshore waters primarily due to these winds
but also for relatively higher seas produced by the passage of
both a northwest and northeast swell. Little change in the overall
nature of these stronger trades and agitated seas with passing
swells has the all-water SCA now in effect through (at least)
Tuesday night. Winds may trend down a touch going into the middle
of next week as the high gets replaced by another slightly weaker
high to the northwest and moves closer to the islands.

The moderate size, long period northwest (320 degree) swell that
peaked yesterday will continue to gradually fall off through early
Monday. This swell decline has allowed the High Surf Advisory (HSA)
to expire along north and west-facing shores. North shore surf will
remain elevated the next few days with eastern exposure surf on the
rise as a fairly large, medium period east northeast (40-60 degree)
swell from a close proximity gale low arrives Monday. East-facing
shore surf heights will likely achieve HSA levels, with surf
potentially reaching warning levels, as this ENE swell peaks Monday
night into Tuesday. Days of fresh to locally strong trades has
produced a rough, short period wind wave, and these rough conditions
are expected to continue along eastern shores with no substantial
break in the trades. Eastern passing southern hemispheric gale lows
will produce swell energy that may eventually make it into our local
waters late this week. South-facing shore surf will probably increase
by another foot or two with the arrival of these small, long period
south swells.


Wind Advisory until 6 PM HST this evening for Kahoolawe-Maui
Windward West-Kohala-Molokai-Lanai Windward-Lanai Leeward-Maui
Central Valley North-Maui Central Valley South-Kipahulu-Big
Island North.

Small Craft Advisory until 6 AM HST Wednesday for all Hawaiian




Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office