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Hawaiian Islands Synoptic Discussion and Guidance

424
FXHW60 PHFO 280643
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
843 PM HST Wed Mar 27 2024

.SYNOPSIS...
Breezy easterly trade winds will become strong and gusty on
Thursday 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 again.

&&

.DISCUSSION...
Guidance remains in good agreement and shows the pressure
gradient steadily tightening across the region overnight through
Thursday as high pressure builds to the north. The easterly
trades will respond and become strong and gusty Thursday through
Friday, particularly on Thursday as the wind speeds peak. This
has prompted a Wind Advisory for the typically windier areas of
Maui County and the Big Island Thursday through Thursday night.
In addition to the winds, spotty windward shower coverage will
persist, especially overnight through the morning periods due to a
sufficient amount of low-level moisture and a lingering 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.

High pressure moving into the area from the west pacific is
expected to elevate island trade winds again into the breezy to
strong range. 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...
Easterly trades will remain gusty as high pressure builds north
of the state. Showers will favor windward locations and rainfall
will be greatest in coverage overnight into the morning hours,
with the occasional spill over to leeward areas. Periods of MVFR
ceilings and visibility will occur within more robust showers.

AIRMET Sierra remains in effect above 2000 feet for north through
east sections of Maui, Oahu and Kauai due to tempo mountain
obscuration from low clouds and showers. This AIRMET will likely
be cancelled later tonight as cloud cover decreases.

AIRMET Tango for tempo moderate turbulence lee of the island
terrain remains in effect as winds near ridgetop have increased
to near 25 to 30 knots. This AIRMET will likely continue into
tomorrow.

&&

.MARINE...
High pressure north of the state will move eastward and
strengthen over the next few days. Easterly trade winds will
respond and increase to strong to gale force through the rest of
the work week. A Gale Warning remains in effect from 6 AM
Thursday through Thursday night for Alenuihaha Channel and has
been expanded to include the Pailolo Channel. A Small Craft
Advisory (SCA) remains in effect through Thursday night 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 which will continue into next week. The current fading small
northwest (310 degree) swell has dropped below seasonal averages
this afternoon. A small medium period reinforcement swell from
the north- northwest (330 degree) is expected late tonight into
Thursday keeping surf elevated 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 Thursday to 6 AM HST Friday for Lanai
Mauka-Maui Windward West-Maui Leeward West-Kohala-Big Island
Interior-Lanai Windward-Lanai Leeward-Big Island North.

Small Craft Advisory from 6 AM Thursday 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-Pailolo Channel-
Big Island Leeward Waters-Big Island Southeast Waters.

Small Craft Advisory until 6 AM HST Thursday for Alenuihaha
Channel.

Gale Warning from 6 AM Thursday to 6 AM HST Friday for
Alenuihaha Channel.

&&
$$

DISCUSSION...Gibbs
AVIATION AND MARINE...Powell

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