Special Marine Warning 1, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
406 PM HST Sat Jan 9 2021

.SYNOPSIS...
An upper level disturbance will bring the threat of isolated
thunderstorms to Maui County through this evening and for the Big
Island through tonight. By Sunday, the disturbance should be away
from the state and we should see the return of light to moderate
trade wind weather. The trades will diminish once again on Tuesday
as a front approaches and moves into the area around midweek.

&&

.DISCUSSION...
A cold upper level trough continues to move closer to the state
this afternoon. Latest sounding from Hilo, shows very steep lapse
rates across the mid levels with lifted index values at -6. A weak
inversion continues to remain at around 7000 feet. Latest radar
and satellite imagery are showing a cluster of thunderstorms
moving into the Maui windward waters. For rest of this afternoon
and evening, the threat of isolated thunderstorms will continue to
exist across Maui County and the Big Island as the upper trough
continues to dig southward toward the state. For Maui, the next
few hours looks to be the greatest chance for any thunderstorm
development. And as the trough continues to moves southward, the
threat of thunderstorms will continue to exist over the Big
Island through tonight, while the chances decrease over Maui
County. The main impacts from any thunderstorms this afternoon and
overnight will be heavy rain and potentially some frequent
lightning.

By Sunday, the front will be dissipated and the upper level
trough will be south of the Big Island. This will allow light to
moderate trades to return and we should see some scattered showers
ride in with the trades.

The light to moderate trades will be short-lived as a front begins
to approach the state on Tuesday. The winds will be light on
Tuesday, but will be gradually veering towards the south ahead of
the front. Fairly dry conditions are likely on Tuesday as the
front approaches. Latest model guidances are in fairly good
agreement with the front within the vicinity of Kauai Wednesday and
making its way through the state sometime Wednesday night.
Although it is still far out in the forecast, this front does not
look very impressive at this time. Stay tuned for more details.

&&

.AVIATION...
Light winds will prevail over most of the state as a dissipating
front stalls near Kauai. Sea breeze conditions will transition to
land breezes as the nighttime hours approach. VFR will prevail
generally, though periods of MVFR in lower clouds and showers have
been affecting randomly distributed areas around the island chain,
mainly in mauka and interior sections on the individual isles.
Most of the cloudiness will clear out as the daytime heating
wanes under this light wind regime. Light to moderate trade winds
will begin returning Sunday. Lastly, with an upper air
disturbance in the area, there is a slight chance of thunderstorms
over Maui and the Big Island through the evening hours.

An AIRMET for high level turbulence remains in effect as the
upper air disturbance passes by.

&&

.MARINE...
A large north northwest swell will build this evening with surf
heights reaching advisory thresholds along north and west facing
shores. A High Surf Advisory is posted for exposed areas through
Sunday night. A Small Craft Advisory is also posted for most
windward coastal waters through Sunday/Sunday night for seas in
areas exposed to this northwest swell. See Marine Weather Message
(MWWHFO) on our website for more information.

As this swell declines on Monday, a large northwest swell will
arrive and continue into Tuesday night and bring another round of
advisory level surf to north and west facing shores. After
another brief drop below advisory levels on Wednesday, yet another
large northwest swell will likely bring advisory level surf to
north and west facing shores Wednesday night through Friday, with
the potential for warning level surf on Thursday.

Surf along east facing shores will remain small into next week with
light to moderate wind speeds. Surf along south facing shores
will remain small through next week with mainly background energy
moving through. A small south southwest swell may give a small
boost to south shore surf around the middle of next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory from in effect to 6 PM HST Sunday for Niihau-
Kauai Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu
Koolau- Molokai-Maui Windward West-Maui Central Valley- Windward
Haleakala.

Small Craft Advisory in effect to 6 PM HST Sunday for Kauai
Northwest Waters-Kauai Windward Waters-Oahu Windward Waters- Kaiwi
Channel-Maui County Windward Waters-Alenuihaha Channel-Big Island
Windward Waters.

&&

DISCUSSION...Kino
AVIATION...Kinel
MARINE...Foster