314
FXHW60 PHFO 191955
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
955 AM HST Sun May 19 2024

.SYNOPSIS...
Clouds and light rain linger today before giving way to a more
typical trade wind pattern from Monday onward.

&&

.DISCUSSION...

The islands remain socked in with overcast skies as the area remains
under a peripheral influence from the kona low, which now sits just
shy of 1000 miles NW of Honolulu. These clouds are associated with
the extensive warm conveyor which extends into the tropics. The
dominant instability axis and surface trough reside along the west
side of this conveyor and should consequently keep heavy rain and
thunderstorms focused west of the islands as well. Nonetheless, the
corridor of gently sloped isentropic ascent draped across the area
will support continued cloud cover and will maintain the existing
shield of stratiform rain that is slowly advancing eastward across
the area. A rogue heavy shower cannot be ruled out, especially in
the vicinity of Kauai, but for all intents and purposes the wet
pattern of the past week has come to an end.

Anticyclonic flow is building over the eastern end of the state
and will continue building westward as the trough associated with
the kona low drifts west. This will bring increasing stability to
the middle and lower portion of the column while eventually
veering the existing locally breezy ESE flow to the more familiar
easterly trade wind direction during Monday. Locally breezy trades
then persist for the balance of the week allowing dewpoints to
fall into the mid to upper 60s and bringing characteristic
increases in showers windward and mauka, particularly overnight
and during the early morning. Periodic intrusions of mid and high
cloud can be expected as the moisture plume with the kona low
resides west of the islands through the week. &&

.AVIATION...

Layered clouds continue to blanket the area this morning. The
clouds appear thickest over Kauai, while thinning over Oahu and
Maui County. While MVFR and IFR conditions are still possible,
particularly over Kauai, improving conditions are expected as the
day progresses. Scattered showers will favor islands west of Maui
and their surrounding waters with isolated activity expected
elsewhere. A slight chance of diurnally driven thunderstorms will
exist over the Big Island this afternoon.

Weak to moderate east southeast background flow will lead to a
land/sea breeze pattern on Kauai, Oahu, and leeward sections of
Maui, Molokai, and the Big Island. A light to moderate trade wind
flow is expected to build in tonight and Monday.

AIRMET TANGO remains in effect for moderate upper level
turbulence from FL250-400 as deep upper level troughing remains
west of the area. This is expected to continue through today and
likely into tonight. AIRMET SIERRA remains in effect for mountain
obscurations over Kauai and Oahu, but with conditions improving,
expect that to be cut back or cancelled altogether later today.
Periods of light to moderate rime icing is expected from Kauai to
Maui in layer 130-FL220, but as the layered clouds break up later
today, conditions should improve. Therefore, AIRMET ZULU is in
effect.

&&

.MARINE...

Locally strong east-southeast winds will persist through Monday
before transitioning to easterly trades Tuesday through the
weekend. A Small Craft Advisory (SCA) remains in effect through 6
PM this evening for the windier waters around Maui County and the
Big Island. This SCA may need to be extended in time with easterly
trades returning.

A pair of overlapping south swells will keep south shore surf near
low-end advisory levels today as a long-period reinforcement
moves through. A High Surf Advisory remains in effect for south
facing shores through this evening. South shore surf will slowly
decline Monday through the middle of the week as the south swell
gradually fades. South shore surf will fall back below the
summertime average on Thursday, followed by a very small long-
period reinforcement near the end of the week.

The current very small northwest swell will gradually ease through
Monday, with north shore surf going to near flat Tuesday through
next weekend.

Surf along east facing shores will remain well below average
for the next couple of days. An upward trend is expected Tuesday
through the weekend as trade winds strengthen over and upstream
of the islands.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening for Niihau-Kauai
Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-Kona-Kauai
South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai Southeast-
Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central
Valley South-South Maui/Upcountry-South Haleakala-Big Island
South-Big Island Southeast.

Small Craft Advisory until 6 PM HST this evening for Maui County
Windward Waters-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters.


&&

$$


DISCUSSION...JVC
AVIATION...M Ballard
MARINE...Vaughan