322
FXHW60 PHFO 170703
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
903 PM HST Thu May 16 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 continue to
produce periods of moderate to heavy showers across portions of
the central and western islands through at least Friday. Satellite
and local radar imagery this evening continue to show a large band
of moderate to heavy showers currently over Oahu. Rainfall rates
under this band are falling around 1 inch per hour. The highest 24
hour rainfall totals over Oahu have reached from 8 to 10 inches in
some locations. A Flood Watch remains in effect for the western
and central islands through Friday.

Impacts through Saturday...Periods of moderate to heavy showers
with the potential for isolated thunderstorms will continue
mainly over Oahu tonight and possibly Molokai and Lanai. This
shower activity will then shift towards Kauai on Friday with
additional bands of showers moving over Oahu. The main flooding
threat will be from bands of showers that line up and train over
any one location, as several hours of 1 to 2 inch rainfall rates
can add up fairly quickly, especially over already saturated
ground. By late Friday the low will begin to drift farther north,
moving away from the islands, and allowing the subtropical ridge
to build back in north of the state. Expect more stable conditions
with decreasing showers as east to southeast winds spreading
across the state from east to west this weekend.

Sunday through Wednesday...By Sunday the moderate to heavy
rainfall threat will linger over Kauai as more stable conditions
move in across the state. Easterly trade winds return from Monday
onward with only brief passing showers in the forecast 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. Moderate to heavy rain showers and
isolated embedded thunderstorms are expected over the western
side islands into Saturday. 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 westward. By
tomorrow afternoon, the heaviest showers will likely be over Kauai
and Kauai Channel.

AIRMET Sierra is in effect for for mtn obsc for Kauai, Oahu,
Molokai, Lanai, Maui and windward Big Island and for IFR conds
over Oahu, Molokai and Lanai.

AIRMET Tango is in effect for turb blw 120 N thru E of the Big
Island.

Occasional light rime icing is expected from Kauai to Maui 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
Friday. 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). 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 later Friday).

Surf along south facing shores will remain up through early next
week due to overlapping, long-period south-southwest swells
expected. The first swell filled in through the day today and will
peak tonight through Friday, likely holding at the advisory
level. Observations at the offshore buoys 51003 and 51004 (51002
remains down) reflect this with the long-period peak energy
shifting into the 15-19 second bands. Expect rough conditions for
most southerly exposures through this period 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 Friday. As this swell slowly eases over the weekend, a
fresh, long-period south-southwest swell will begin to fill in
through the day Sunday. This will peak at a similar level early
next week before easing through midweek.

Surf along north and west facing shores has trended up through the
day due to a short-period northwest swell generated from the
nearby kona low. This swell will linger Friday (largest Kauai),
then ease 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 Friday evening for the islands of Kauai,
Niihau, Oahu, Molokai and Lanai.

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

Wind Advisory until 4 AM HST Friday for Big Island Summits.

Small Craft Advisory until 6 PM HST Friday for Big Island
Windward Waters-Big Island Leeward Waters.

&&

$$

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