442
FXHW60 PHFO 200116
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
316 PM HST Sun May 19 2024

.SYNOPSIS...
Clouds and areas of light rain linger into tonight. Locally breezy
trades return during Monday and continue through the week
bringing periodic clouds and showers to windward and mauka areas.


&&

.DISCUSSION...

Clouds and embedded disorganized areas of light stratiform rain
are slowly advancing east across the forecast area this evening.
As the kona low, now around 1000 miles NW of Honolulu, lifts
north and west veering mid-level flow will steer this activity SE
of the area overnight. The other area of cloud cover is anchored
along the surface trough and low-level instability axis. This
corridor of ascent and attendant clouds and heavy showers will
continue to drift westward away from the islands during the next
couple of days. As anticyclonic flow builds into the state from
the east, there will be enough breaks in low and mid-level cloud
cover to allow the sun to emerge on Monday. Returning trades will
deliver periodic low clouds and showers to windward and mauka
areas for the remainder of the week.

&&

.AVIATION...

Layered clouds over the region have started to thin. A few
lingering high clouds remain over Kauai this afternoon, revealing
VFR conditions over the Garden Isle. The AIRMET for mountain
obscuration has been canceled for Kauai, but as trade wind clouds
and showers pick up overnight and Monday, another AIRMET may be
needed for the east side of the island.

Layered clouds over Oahu continue to bring some mountain
obscurations, so AIRMET SIERRA continues for Oahu. Conditions are
expected to improve overnight, so anticipating the AIRMET will be
cancelled, or scaled back as conditions improve.

High clouds remain over Maui County, but VFR conditions continue
to dominate, although some pockets of MVFR in passing clouds and
showers continue.

The layered clouds have moved down over the Big Island over the
last few hours, and additional low level clouds have moved in from
the east, and developed over the island. AIRMET Sierra was posted
for mountain obscuration on the east side of the island, but may
need to be expanded. Conditions are expected to improve overnight,
but AIRMET Sierra may linger over the east side of the island with
additional low level clouds moving in from the east.

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 into tonight.
AIRMET Zulu is in effect for areas of light to moderate rime
icing in the layered clouds from Oahu to the Big Island. As
alluded to above, as the layered clouds break up later
tonight, conditions should improve.

&&

.MARINE...

Locally strong east-southeast winds will persist through Monday
before transitioning to easterly trades Tuesday through the
weekend. The Small Craft Advisory (SCA) has been extended through
Monday afternoon for the windier waters around Maui County and
the Big Island. This SCA may need to be extended further in time
with easterly trades returning, and could also include additional
zones.

Latest surf observations show that surf along south facing shores
continues to be at advisory levels this afternoon. The Lanai buoy
(51203) shows the current reinforcing south swell above guidance
at about 3.5 feet 18 seconds, and spectral density plots from
bouy 51003 suggest an additional bump of energy in the 16-17
second range moving into south facing shores this evening and
tonight. Therefore, the High Surf Advisory for south facing shores
has been extended through tonight for now, though it is possible
surf heights could linger at borderline advisory levels through Monday
morning. South shore surf is expected to slowly decline Monday
through the middle of the week as the south swell gradually fades,
then will fall back below the summertime average on Wednesday. A
very small, long-period reinforcement will arrive Thursday and
linger through 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 AM HST Monday 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 Monday for Maui County
Windward Waters-Alenuihaha Channel-Big Island Windward Waters- Big
Island Leeward Waters.


&&

$$


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