875
FXHW60 PHFO 121316
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
316 AM HST Wed Mar 12 2025

.SYNOPSIS...
Breezy to windy trades will persist today and then show decreasing
trends from Thursday onward. A fairly stable atmosphere will allow
just a few passing showers to develop, mainly over windward and
mountain areas, favoring the overnight to early morning hours.
Winds will weaken and shift from a more southeasterly direction by
this weekend, allowing sea breezes to expand in coverage along
terrain sheltered western mountain slopes. An upper level low
moving into the Hawaii Region from the northwest may enhance
shower activity across the state from Saturday into early next
week.

&&

.DISCUSSION...
A few bands of low topped clouds are seen on the latest satellite
imagery this morning moving into each island on the trade winds.
Local doppler radar imagery shows scattered showers drifting into
windward island mountains. Brief passing showers will continue
through the early morning hours as these cloud bands are forced
up our island mountain slopes. Daytime diurnal drying trends will
decrease shower activity after 8 AM HST this morning with more
isolated showers forecast until the evening hours. Large scale
subsidence (downward moving air) from the high pressure ridge
aloft will tend to limit shower production over the Hawaii Region
over the next several days. The atmosphere remains fairly stable
with temperature inversion heights, as measured from weather
balloon soundings at 2 AM HST (12Z) this morning, are hovering
around the 5,000 foot level at both Lihue and Hilo. These low
temperature inversion heights will continue to limit vertical
cloud heights and shower activity through Friday.

A strong high pressure system just north of the Hawaiian Islands
will continue to produce breezy to windy trades today. The current
Wind Advisory for windier areas of Maui County and the Big Island
was extended in time until this evening to cover these strong
and gusty winds. Wind speeds will noticeably decrease on Thursday
and decrease even lower on Friday as the high pressure system
north of the island chain drifts slowly eastward farther away
from the state. Sea breezes will expand in coverage over all
islands by this weekend as large scale trade winds weaken. A
hybrid sea breeze and east to southeast wind pattern will produce
some wind convergence boundaries and cloud build ups over each
island by this weekend.

A weakening cold frontal system approaches the islands from the
northwest direction from Thursday to Friday. This system will
stall out several hundred miles west of Kauai. Cold air
surrounding this system will form an upper level cold core low
that will be cut off from the mid-latitude westerlies. This cut
off low will slowly drift eastward towards Hawaii over the
weekend. Cold temperatures and wind divergence aloft along the
east side of the low will weaken the large scale subsidence over
the western half of the state, allowing deeper clouds and
enhanced showers to develop in this pattern. This upper low will
weaken the surface ridge, causing wind speeds to decrease and
winds to veer from a more east to southeast direction. Any
enhanced showers will tend to form along any wind convergence
boundaries in a hybrid sea breeze wind pattern, or leeside island
convergence plumes that may potentially be drawn northward into
the smaller islands. Instability aloft associated with the cut off
low will deepen cloud convection along these boundaries and
possibly produce some periods of moderate to locally heavy shower
activity. The chances for enhanced showers will increase for the
western islands as they are much closer to the low center.
Enhanced showers are also expected along east and southeast slopes
of the Big Island from Sunday into the first half of next week.

The latest long range model solutions and blends continue to show
the upper low and the associated surface trough reflection
stalling out near Kauai from Sunday through Tuesday. This means
this unsettled weather pattern over the western islands may
continue through the first half of next week. Stay tuned.

&&

.AVIATION...
High pressure north of the islands will maintain breezy to strong
trade winds across the region. AIRMET Tango remains in effect for
moderate low level mechanical turbulence to the lee of the
mountains. As breezy trades are expected to persist, this AIRMET
will likely remain in place over the next couple of days.

Bands of clouds and light showers off the Pacific will impact
mainly north and east facing slopes and coasts. Showers will be
most active in the late night and morning hours.

AIRMET Sierra for mountain obscuration is currently in effect for
windward exposures of Kauai and Oahu. Conditions are expected to
persist through the morning hours, but VFR conditions should
prevail statewide by mid afternoon.

&&

.MARINE...
Strong high pressure far north of the state will drift slowly
eastward keeping strong to locally near gale force winds today
before declining slowly through Thursday. The Gale Warning for
Maalea Bay and the Pailolo and Alenuihaha Channels has been
downgraded to a Small Craft Advisory and will remain for all zones
due to strong trades and elevated seas through the day. A trough
looks to develop northwest of the state, which will cause the
trade winds to veer toward the east by Friday. Moderate to fresh
east to east- southeast winds will likely persist through the
weekend.

A moderate size, medium to long period north northwest (330
degree) swell will build through the day, peak this afternoon, and
decline Thursday. Long period forerunners have begun to arrive
early this morning at PacIOOS Hanalei Buoy as surf looks to peak
this afternoon just below High Surf Advisory criteria for north
and west facing shores. A similar sized west northwest (300 to
320 degree) swell is scheduled to arrive Thursday night and peak
Friday at or near High Surf Advisory levels.

Surf along east facing shores will remain rough and choppy just
below High Surf Criteria due to strong trade winds over and
upstream of the islands through Thursday before declining slightly
Friday and into the weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM HST this evening for Lanai Mauka-
Kahoolawe-Maui Windward West-Maui Leeward West-Kohala-Lanai
Windward-Lanai Leeward-Maui Central Valley North-Maui Central
Valley South-South Haleakala-Big Island South-Big Island
Southeast-Big Island North.

Small Craft Advisory until 6 PM HST this evening for all
Hawaiian waters-

&&

$$

DISCUSSION...Bohlin
AVIATION...Bedal
MARINE...Shigesato