372
FXHW60 PHFO 171351
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
351 AM HST Fri May 17 2024

.SYNOPSIS...
A kona low north of the state will continue drawing unstable
tropical moisture northward over the islands into Saturday. Bands
of showers producing moderate to heavy rain and isolated
thunderstorms will move over the central and western islands
tonight through at least Friday. The kona low will begin to drift
away from the state this weekend with improving trends spreading
from east to west. Enhanced rainfall may linger over Kauai and
Niihau into Sunday. By Monday all islands will see a dramatic
improvement in weather conditions as easterly trade winds return.

&&

.DISCUSSION...
A kona low northwest of the Hawaiian Islands will begin to slowly
drift north away from the state today. A low level trough
currently over Oahu will continue to produce periods of moderate
to heavy showers across the western islands into the evening
hours. Most of the heavy rain and flooding threat will occur along
this trough shower band. The highest 24 hour rainfall totals over
Oahu have reached around 10 inches in some locations. A Flood
Watch remains in effect for the western islands into the evening,
the Flood Watch for Oahu may be cancelled later today as this
shower band moves westward into the Kauai Channel.

The latest satellite and local radar imagery this morning shows
this shower band moving slowly westward through Oahu this morning
where continued rainfall is expected until around mid morning.
This shower band will then move into the Kauai Channel and
approach Kauai from the east. Shower activity over Kauai will
increase from late morning through the overnight hours as this
shower band slowly moves over the garden isle. Rainfall rates
under this band are falling up to 1 inch per hour.

Saturday and Sunday...The high pressure ridge will slowly build in
north of the island chain this weekend, as the kona low exits the
pattern to the north. Expect more stabilizing trends with
decreasing showers as east to southeast winds spread across the
state. By Sunday, the moderate to heavy rainfall threat will
diminish over Kauai as more stable conditions fill in across the
state.

Monday through Wednesday...More typical easterly trade winds
return across Hawaii nei from Monday onward with only brief
passing showers in the forecast favoring the typical windward and
mountain areas through the middle of next week.

&&

.AVIATION...
A strong kona low NNW of Kauai is pulling tropical moisture out
of the south across the state. This will keep the the islands in
an showery weather pattern through the weekend. Moderate to heavy
rain showers and isolated embedded thunderstorms are expected
over the western side islands through this evening. On the Big
Island, shower activity will taper off during the nighttime hours
only to redevelop during the afternoons and early evenings.

Latest radar imagery reveals the heaviest showers over Oahu and
the Kaiwi channel. This band is expected to slide gradually westward.
By this evening, the heaviest showers will likely be over Kauai
and Kauai Channel.

AIRMET Sierra is in effect for  Kauai, Oahu, Molokai, Lanai, and
windward Big Island. IFR conds over Kauai, Oahu, Molokai and Lanai
will likely improve towards noon, but mountain obscuration will
likely remain an issue for Oahu and Kauai through twenty-four
hours.

AIRMET Tango is in effect for low level mechanical turbulence
north through east of the Big Island and East Maui.

Occasional light rime icing is expected from Kauai to Molokai in
layer 140-FL250.

&&

.MARINE...
Fresh to locally strong south to southeast winds associated with
a kona low north-northwest of the state will persist through
tonight. A shift out of the east to southeast direction is
expected over the weekend through early next week as it lifts
northward and away from the area. A Small Craft Advisory remains
in effect for the Windward and Leeward Big Island waters (Hamakua
Coast and waters near South Point) through tonight. In addition to
the winds, expect locally rough seas in heavy showers or storms
that develop, with the best chances being over the waters west of
Maui County. Seas should remain just below the advisory level over
the exposed Kauai waters as a short-period northwest swell moves
through (downward trend expected this weekend).

Surf along south facing shores will remain up through early next
week due to overlapping, long-period south-southwest swells
expected. The first swell has filled in and will peak today,
likely holding at the advisory level into Saturday before briefly
lowering. Observations at offshore buoys 51003 and 51004 (51002
remains down) reflect this with the long-period peak energy now in
the 15-17 second bands. Expect rough conditions for most
southerly exposures today due to a combination of the onshore
winds, swell, and periodic heavy showers moving through. As a
result, a High Surf Advisory remains in effect through Saturday. A
fresh, long-period south-southwest swell will begin to fill in
through the day Sunday, then peak at a similar level early next
week before easing through midweek.

Surf along north and west facing shores will remain up into
Saturday due to a short-period northwest swell generated from the
kona low. This swell will lower over the weekend.

Surf along east facing shores will remain well below average
through the weekend. An upward trend is possible next week as the
trades return locally and far upstream over the eastern Pacific.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through this evening for Kauai, Niihau and Oahu.

Wind Advisory until 6 PM HST this evening for Big Island Summits.

High Surf Advisory until 6 PM HST Saturday for south facing
shores.

Small Craft Advisory until 6 AM HST Saturday for Big Island
Windward Waters-Big Island Leeward Waters.

&&

$$

DISCUSSION...Bohlin
AVIATION...Bedal
MARINE...Gibbs