FXHW60 PHFO 051343
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
343 AM HST Tue Mar 5 2024

.SYNOPSIS...

A wet trade wind pattern with isolated thunderstorms and locally
heavy rain, especially over windward areas, will prevail through
Wednesday night. Breezy trades will further strengthen during the
middle part of the week.


&&

.DISCUSSION...
Overall the forecast seems to be on track, so no changes to the
short term forecast with the morning package. Overnight saw
showers carried in on the trades focused over the windward and
mauka slopes. Kauai, Maui and the Big Island experienced the
heavier showers, and on the Big Island, a few of the area stream
gages did respond. Fortunately there has been enough of a break in
the showers for the streams to periodically get a break an

High pressure to the north, and a weakening surface trough moving
west away from the main Hawaiian islands is helping to bring
breezy trade winds to the region. An upper level trough sinking
southward over the islands is responsible for the unstable
airmass, allowing trade wind showers to be more intense than
normal. In addition, this instability could trigger a few
thunderstorms.

This set up over the next couple of days will continue the wet
trade wind weather with the potential for moderate to locally
heavy rain focused windward and mauka, particularly over the
western end of the state through early Tuesday morning and the
Big Island and Maui Tuesday and Wednesday.

The Winter Storm Warning remains in effect through Tuesday night
for the Big Island, with the primary concern being freezing rain
leading to ice accumulation.

As the above mentioned upper level trough lingers over the
islands, a couple more rounds of moderate to locally heavy rain
potential exist both Tuesday night and Wednesday night. In both
cases, the focus is expected to be mainly over Maui and the Big
Island, but can't completely rule out Oahu and Kauai from seeing
additional showers.

Trade winds will linger through the week with high pressure to the
north. Winds are expected to increase mid-week so the above
mentioned surface trough dissipates. Toward the end of the week,
the high will move to the east, and be replaced by a new high,
which will maintain the moderate to locally windy trade winds.

From Thursday on into the weekend the upper level trough lifts to
the north and northeast, just enough to cut off some of the
instability that is leading to the heavier showers. As such look
for a return to a more typical trade wind pattern.


&&

.AVIATION...

Moderate to breezy trade winds will persist for the next several
days as strong surface high pressure holds north of the state.
Clouds and showers will favor windward slopes and coasts. Periods of
MVFR conditions with low ceilings and visibility in showers are
expected mainly over windward airfields, especially in the late
night and morning hours.

A deepening upper level trough will enhance convective activity.
There is a slight chance of thunderstorms statewide through forty-
eight hours and possibly beyond.

AIRMET Sierra is now in effect for northeast facing slopes of
Kauai, Oahu, and the Big Island. Conditions are expected to
improve later this morning.

AIRMET Tango is in effect for moderate leeward mountain wave
turbulence over all islands due to breezy trade winds, and is
expected to remain necessary through twenty-four hours and
possibly beyond. Additionally, areas of moderate upper level
turbulence remain an issue for the eastern third of the state.
Upper level turbulence conditions are expected to rapidly improve
this morning as the subtropical jet shifts to the east.


&&

.MARINE...
A strong high pressure system will drift eastward, slowly passing
north of Hawaii over the next few days. Expect strong to near-
gale east-northeast trade winds through much of this week as
another strong high pressure system builds into the region from
the west as the first one retreats eastward on Thursday. A Small
Craft Advisory remains in effect for all waters, and will likely
remain in place through much of this week. A persistent trough
aloft will keep the island atmosphere unstable, with briefly heavy
showers producing periods of strong wind gusts and low visibility.
Isolated thunderstorms are also in the forecast into Thursday.

The persistent trade winds will generate rough and choppy surf along
east facing shores through the week. Gradually diminishing
medium period swells out of the northwest and north will continue
to trend down today. A small, medium period northwest swell will
arrive on Wednesday. Followed by a larger and longer period
northwest swell, building surf heights to near advisory thresholds
along exposed north and west facing shores from Friday to
Saturday.

South shores will remain seasonably small with mainly medium
period background swell energy pulses.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM HST Wednesday for Big Island
Summits.

Small Craft Advisory until 6 AM HST Thursday for all Hawaiian
waters-


&&

$$


DISCUSSION...M Ballard
AVIATION...Bedal
MARINE...Bohlin