614
FXHW60 PHFO 202000
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
1000 AM HST Mon May 20 2024

.SYNOPSIS...
The low pressure system far north of the state will continue to
drift slowly northward over the next few days as high pressure
builds back into the region. Expect moderate to locally breezy
east to east-southeast winds over most islands through midweek,
though wind directions will be modified by local scale daytime sea
breezes over sheltered areas of each island. Brief passing
showers will favor mainly windward and mountain areas,
particularly during the overnight through early morning hours. A
disturbance will move through the islands from Tuesday night
through Thursday morning, increasing windward and mauka showers
midweek.

&&

.DISCUSSION...
High pressure is building back into the region today as the low
pressure north of the state and a trough to the northwest
continues to drifts slowly away from the main Hawaiian Islands.
Latest satellite imagery this morning shows only a few clouds
moving into windward and mountain areas with isolated to scattered
showers. Most interior and leeward areas are experiencing mostly
sunny to partly cloudy conditions this morning. A strong
inversion was noted around 5,000 feet in the early morning Hilo
sounding. With increasing stability and low inversion heights
spreading westward, vertical cloud development and shower coverage
will be rather limited today through Tuesday. Expect moderate to
locally breezy east to east-southeast winds over the eastern half
of the state and moderate winds over the western half through
midweek. However, localized sea breezes will be possible during
the daytime over sheltered areas. This will cause clouds to build
over island interior sections today and Tuesday, though showers
will remain limited.

Low pressure aloft associated with the kona low to the north of
the state will swing around and develop into a new trough and
eventual low in the mid- to upper levels. A weak surface low is
forecast to develop just south of 30N by late Tuesday through
Thursday. Meanwhile, a developing shortwave aloft will move into
the eastern islands late Tuesday. This combination could increase
moisture depth and result in and increase in windward and mauka
showers spreading across the island chain from west to east from
Tuesday night through Thursday morning, particularly during the
overnight through early morning hours.

From Thursday through the rest of the week, easterly trade winds
spread to all islands. Broad upper level troughing will keep
passing showers mainly during the overnight to early morning hours
favoring windward and mountain areas.

&&

.AVIATION...
A surface trough to the west is continuing to move away from the
area and will allow a surface trough north of the islands to
strengthen. This will allow light to moderate east to southeast
winds to transition to moderate trade winds later today and
tonight. VFR conditions will prevail with brief MVFR conditions
over windward slopes in passing clouds and showers. No AIRMETs are
in effect and none are expected today.

&&

.MARINE...
A trough of low pressure far northwest of the state and a strong
high far northeast of the state will produced fresh to strong
trade winds over the eastern half of the state and moderate trades
over the western half of the state through Tuesday. A Small Craft
Advisory is in effect for the windier zones around Maui County and
the Big Island. Starting late Tuesday night into Wednesday,
another trough will develop west of the state and will cause the
winds to weaken and veer toward the southeast over the western
half of the state. By Thursday, the trough should weaken and we
should see fresh to locally strong trades across the state through
the rest of the week.

Surf along south-facing shores will remain at or near advisory
heights through the day today. Recent south shore buoys
observations show a swell of 3 to 4 feet with a periods of 16 to
17 seconds. The current south swell should gradually fade over the
next few days and should drop below advisory thresholds by Tuesday.
Surf along east facing shores should see a gradual rise over the
next several days as the trades strengthen upstream of the state.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening for all south
facing shores.

Small Craft Advisory until 6 AM HST Tuesday for Maui County
Windward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-
Big Island Windward Waters-Big Island Leeward Waters-Big Island
Southeast Waters.

&&

$$

DISCUSSION...Vaughan
AVIATION...M Ballard
MARINE...Kino