Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 241928
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
928 AM HST Sun Mar 24 2024

.SYNOPSIS...
Breezy easterly trade winds will ease tonight and Monday as
surface high pressure to the northeast weakens and drifts to the
east. High pressure will rebuild north of the state on Wednesday,
leading to breezy and gusty trade winds through at least Friday.
Rainfall will favor typical windward slopes through much of the
week, and a nearby low aloft will produce areas of high clouds
through Monday.

&&

.DISCUSSION...
A somewhat dry and stable easterly trade wind flow will prevail
today. A 1034 mb high sitting about 900 miles northeast of the
state has been driving the breezy trade winds during the past
couple of days. A surface ridge extending from the high runs to
about 475 miles north of Kauai, and as this ridge has been pushed
slowly southward, local trade winds have become more easterly and
have decreased slightly in most areas. As a result, the Wind
Advisory for lower elevations of the Big Island has been
cancelled. A mid-level ridge continues to produce stable
conditions with an inversion based between 6,000 to 7,000 ft, and
the upwind environment is dominated by stable stratocumulus with
precipitable water below an inch. This points toward minimal
windward rainfall today, and aside from a few showers over the
Kona slopes of the Big Island, leeward areas should be dry. A low
aloft centered several hundred miles to the south may produce
strong winds on the high summits of the Big Island, where a Wind
Advisory remains in place, while associated areas of thin high
clouds pass over the island chain.

Easterly trade winds will ease to moderate strength tonight and
Monday as the high and its associated ridge weaken and drift
eastward. The low aloft will meander a little closer to the state
but will be weakening. Guidance still suggests that weak low- to
mid-level ridging will inhibit a significant increase in rainfall,
but a few spotty showers cannot be ruled out over leeward terrain
Monday and Tuesday afternoon and evening.

A return to breezy and gusty trade winds will occur Wednesday
into at least Friday as another strong surface high sets up north
of the state. The forecast favors a typical pattern of mainly
windward showers during this time. However, the GFS and ECMWF are
both showing a band of moisture boosting windward rainfall Friday
or Saturday but vary on timing.

&&

.AVIATION...
A high pressure system northeast of Hawaii will keep breezy and
gusty trade winds in the forecast today with decreasing wind
speed trends starting on Monday. Brief showers and MVFR conditions
will favor windward and mountain areas during the overnight to
early morning hours.

AIRMET TANGO remains in effect for moderate low-level mechanical
turbulence over and downslope of the mountains. Expect this to
remain in place through the rest of the weekend. AIRMET TANGO for
upper level turbulence between Oahu and the Big Island has been
cancelled due to being covered by SIGMET series Quebec. This
turbulence is due to a portion of the subtropical jet bending
around an upper low over the islands, and is expected to slowly
weaken through the afternoon hours. Anticipating downgrading the
SIGMET area over the islands to an AIRMET TANGO later today.

&&

.MARINE...
High pressure to our northeast will drift eastward over the next
few days, causing trades to weaken into the moderate to fresh
range. However, another high forecast to build north of the
islands will cause trades to increase into the strong to near
gale range during the second half of the week. A Small Craft
Advisory (SCA) remains in effect for strong winds across all
Hawaiian waters through this afternoon. However, because an
incoming northwest swell will boost wave heights tonight and
Monday to SCA levels as well, most Hawaiian waters are included
in an extended SCA through Monday.

The current moderate long period northwest swell is slowly
subsiding and surf along exposed shores will continue to drop
through the day. A slightly larger west-northwest to northwest
swell is showing on the offshore buoys this morning. This swell
will reach the islands this afternoon and build tonight, raising
surf along exposed shores to High Surf Advisory (HSA) levels
tonight and Monday. This swell will contribute with winds to raise
combined seas above 10 feet over coastal waters to the east of
the islands tonight and Monday, which would maintain an SCA for
those waters. Due to the westerly component of this swell, surf
heights may approach HSA thresholds for west facing shores of the
Big Island on Monday.

Short period easterly wind wave swell will remain elevated and
choppy as trade winds remain strong. As trades strengthen even
further later next week, we should see another uptick along east
facing shores during the second half of next week. South-facing
shore surf will remain at background levels for the next several
days.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM HST this evening for Big Island Summits.

Small Craft Advisory until 6 PM HST Monday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Channel-Oahu Windward Waters-
Kaiwi Channel-Maui County Windward Waters-Maui County Leeward
Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Waters.

Small Craft Advisory until 6 PM HST this evening for Kauai
Leeward Waters-Oahu Leeward Waters.

&&

$$

DISCUSSION...Wroe
AVIATION...TS
MARINE...Powell


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