FXHW60 PHFO 090133
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
333 PM HST Thu Feb 8 2024

.SYNOPSIS...
Easterly trade winds will gradually ease through Saturday as a
surface ridge to the north weakens. Modest showers will be focused
over windward and mauka slopes, while most leeward areas remain
rather dry. Trade winds will break down Sunday and Monday, leading
to a land and sea breeze pattern with limited showers. A shallow
dissipating front is expected drift over Kauai and Oahu Monday
night and Tuesday under light northerly winds. Southwesterly
winds are expected to develop around Wednesday as a stronger front
approaches.

&&

.DISCUSSION...
The stable, easterly trade wind flow will be on a slow decline for
a couple of days. The surface high that had been driving the
recent gusty trade winds is moving eastward, away from the
islands, and weakening, while its trailing surface ridge located
over 250 miles north of Kauai is eroding. The easterly trade
winds winds will slowly ease through Saturday, with the strongest
winds hanging on around the Big Island. A strong mid level ridge
overhead is producing very stable conditions with an inversion
based below 7,500 ft, and the precipitable water within the trade
wind flow is currently an inch or less. Under these stable
conditions, expect windward rainfall to be modest and to favor
windward Big Island tonight, then shift up the island chain
Friday as a shallow batch of moisture moves through. Aside from
spotty afternoon showers on the Kona slopes of the Big Island,
leeward areas will remain rather dry.

Trades will veer southeasterly Saturday night and break down on
Sunday as the surface ridge to the north is further weakened by an
approaching front. The GFS and ECMWF have not been consistent in
their handling of this pattern, but both models have suggested
that the front will be rapidly weakening and that a weak surface
ridge could develop west of Kauai. This would result in a weak
surface trough forming across the central portion of the island
chain on Sunday. If this occurs, we would see a few more showers
near the trough axis somewhere between Oahu and Maui, but even
though the mid level ridge overhead will weaken, conditions
overall should remain stable and lower any chance of heavy shower
development. Elsewhere, expect a land and sea breeze pattern with
limited interior rainfall Sunday afternoon.

A rather dry and light northwesterly flow on Monday will give way
to northerly winds that should push the dissipating and shallow
front down to Kauai or Oahu on Tuesday. These islands will likely
experience some light shower activity, but little rainfall is
expected elsewhere.

Southwesterly winds are expected to develop around Wednesday and
could become gusty as a stronger front approaches. Timing on this
frontal passage is uncertain but favors next Thursday.

&&

.AVIATION...
Light to moderate easterly trade winds will shift to be out of
the east-southeast by tomorrow afternoon in response to a distant
cold front. Bands of light showers off the Pacific will impact
mainly east and southeast facing slopes and coasts. Isolated
spillover showers are likely over leeward portions of the smaller
islands, especially in the late night and morning hours.

For leeward and interior Big Island, local sea breezes will give
way to weak land breezes after sunset. Overnight clearing is
expected along west facing slopes and coasts, but sea breezes and
inland cloudiness can be expected to return Friday afternoon.

Shower activity is expected to increase during the overnight
hours. Mountain obscuration could become an issue for portions of
windward Big Island later this evening. Otherwise, VFR conditions
will prevail except for brief MVFR in passing showers.

&&

.MARINE...
A high pressure system far northeast of the state will continue to
drift slowly eastward away from the islands through Friday. A low
pressure system and trough approaching the islands from the northwest
will weaken the ridge north of the islands through the first half
of next week. Trade wind speeds will continue to weaken into the
weekend, with light to moderate winds forecast over the western
islands starting on Friday, then the entire state by Sunday. The
Small Craft Advisory (SCA) has now been cancelled, as winds and
seas continue to ease.

The northeast swell will continue to diminish through Friday. Surf
heights along north and west facing shores will continue to slowly
decline today as the current northwest (310 deg) swell diminishes.
Models show another moderate northwest (310-320 deg) swell moving
into the region Friday into the weekend. This swell is not even
evident at Buoy 51001 far northwest of Kauai as of 2 PM HST, so it
will likely be running a bit late and have lowered surf heights
slightly for Friday as a result. Surf heights could approach advisory
levels late Friday afternoon or evening for exposed north and west
facing shores, but will monitor the swell as it arrives at the offshore
buoys tonight. This northwest swell will then decline through the
first half of next week. Wave guidance is indicating the potential
for an extra large, long- period northwest (320 deg) swell arriving
around next Thursday, with the potential for surf well above warning
levels along exposed north and west facing shores. This situation
will be closely monitored over the next several days.

Expect small background south swell pulses to continue through the
middle of next week. A small, long-period south (200-220 deg) swell
with Tasman Sea origins may produce a slight bump in south shore
surf from Friday through Sunday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Wroe
AVIATION...Bedal
MARINE...TS