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Hawaiian Islands Synoptic Discussion and Guidance

772
FXHW60 PHFO 281323
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
323 AM HST Thu Mar 28 2024

.SYNOPSIS...
Strong and gusty easterly trade winds are expected into Friday as
high pressure strengthens north of the state. Showers will favor
windward and mountain areas with some reaching the leeward areas.
Drier and more stable conditions will return over the weekend,
with the easterly trades easing into the moderate to breezy range.
Rainfall chances could trend up again early next week as an upper
disturbance moves through and trade winds increase.

&&

.DISCUSSION...
Guidance remains in good agreement and shows the pressure
gradient steadily tightening across the region today as high
pressure builds to the north. The easterly trades are responding
and will become strong and gusty today through tonight as they
peak. This has prompted a Wind Advisory for the typically windier
areas of Maui County and the Big Island. In addition to the winds,
spotty windward shower coverage is expected, especially overnight
through the morning periods due to a sufficient amount of low-
level moisture and a weak upper trough in the area. These showers
will be brief with minimal accumulations anticipated.

Drier and more stable conditions will briefly return over the
weekend as upper heights rise and PWs dip to around an inch. Trade
winds are expected to ease into the moderate range due to a
weakness forming in the ridge as a front passes to the north.

A return of breezy to strong trades is anticipated through the
first half of next week as high pressure builds north of the state
(near 1050 mb). Model differences still remain with the GFS being
stronger with the winds, while the ECMWF has a more moderate
solution. Regardless of these differences, both depict an upper
trough digging southward over the region creating an increased
chance of heavier trade wind showers Monday through midweek.

&&

.AVIATION...
Surface high pressure due N of the islands will support locally
strong trade winds through Friday. Although the island atmosphere
will be capped by a subsidence inversion based near 8 kft, showery
low clouds will produce periods of MVFR VIS/CIG, mainly over windward
slopes and coasts. Spatial and temporal coverage is not expected
to be sufficiently significant to warrant an AIRMET for mountain
obscuration, but AIRMET Tango for tempo moderate turbulence lee of
the island terrain will remain in effect.

&&

.MARINE...
Trade winds will increase into the strong to gale force range
through the rest of the work week. A Gale Warning remains in
effect from 6 AM this morning through 6 AM Friday morning for the
Alenuihaha and Pailolo Channels. A Small Craft Advisory (SCA)
remains in effect through tonight for all remaining coastal
waters. Next week, another high pressure building in from the
northwest is expected to continue the breezy trend across the
coastal waters.

Strong trades will create rough and choppy surf along east facing
shores into next week. A small medium period swell from the
north-northwest (330 degree) will arrive this morning, keeping
surf elevated but far below advisory level across north and west
facing shores. A series of small medium to long period northwest
swells are expected through early next week. Mainly background
surf will continue for south facing shores through the weekend
with some long period energy arriving early next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 6 AM this morning to 6 AM HST Friday for
Lanai Mauka-Maui Windward West-Maui Leeward West-Kohala-Big
Island Interior-Lanai Windward-Lanai Leeward-Maui Central Valley
North-Maui Central Valley South-Windward Haleakala-South
Haleakala-Big Island Southeast-Big Island North.

Small Craft Advisory from 6 AM this morning to 6 AM HST Friday
for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Big Island Windward Waters.

Small Craft Advisory until 6 AM HST Friday for Oahu Windward
Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward
Waters-Maui County Leeward Waters-Maalaea Bay-Big Island Leeward
Waters-Big Island Southeast Waters.

Small Craft Advisory until 6 AM HST early this morning for
Pailolo Channel-Alenuihaha Channel.

Gale Warning from 6 AM this morning to 6 AM HST Friday for
Pailolo Channel-Alenuihaha Channel.


&&

$$


DISCUSSION...Gibbs
AVIATION...Birchard
MARINE...Powell

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