Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 020630
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Thu Dec 1 2022

.SYNOPSIS...
Trade winds will strengthen to moderate to locally breezy Friday,
and continue through the weekend, maintaining showers across
windward areas. A system developing northwest of the state late in
the weekend, may increase moisture and strengthen southeast
winds, potentially enhancing shower chances next week.

&&

.DISCUSSION...
A slight chance of showers and thunderstorms remains in the
forecast over the Mauna Loa summit through the weekend, where
lava-induced extreme heating of the lower atmosphere will spur
occasional development of pyrocumulonimbus clouds.

Current radar trends show limited showers across the state this
evening, with a majority of showers concentrated in the
vicinity of the Big Island and Maui, as deeper layered moisture
(moisture depths between 8-10k ft) and weak instability linger
in that area. Otherwise, much drier (modeled moisture depths
under 7k ft) and much more stable air, remains anchored over the
remainder of the western and central islands, limiting showers and
clouds for these areas tonight. Overall expect limited showers
across windward areas of Kauai through Oahu through Friday
morning, while scattered showers linger around the eastern end of
the state.

Friday through the Sunday afternoon...easterly trade winds will
strengthen to moderate to locally breezy and continue through the
weekend, as a ridge of high pressure lingers north of the state.
This will generate a trade wind weather pattern across the state,
with showers embedded in the trades focused across mainly
windward and mauka zones. The areal coverage of showers will
increase slightly during the overnight and early morning periods.
Showers may occasionally drift to leeward locations at times.
Rainfall rates will remain limited through Sunday afternoon, as
surface and upper level ridging in place over the state,
maintains a mainly stable airmass.

Sunday night through next week...deterministic guidance remains
in agreement with a mid-latitude trough rapidly amplifying east of
the Dateline Sunday night and closing off northwest of Kauai
Monday. Additionally, at the surface, a low is forecast to develop
and strengthen northwest of Kauai by Monday, with current
forecast trends suggesting this feature will remain west of Kauai
and drift slowly westward, causing winds to become mainly
southeasterly across the island chain. This will potentially
increase moisture and enhance rainfall chances across portions of
the state through the middle of next week. This time period
certainly bears monitoring, especially over the western end of the
state.



&&

.AVIATION...
A high pressure ridge far north of the region will keep light to
moderate trade winds in the forecast through Saturday. Clouds and
passing showers will favor the windward and mountain areas of
Molokai, Maui and the windward slopes of the Big Island through
Friday morning, with only brief showers along windward slopes of
Oahu and Kauai.

AIRMET Sierra in effect for Tempo Mountain Obscuration above 020
elevation due to clouds and SHRA over portions of Maui and the Big
Island.

&&

.MARINE...
Large surface high pressure centered approximated 1,400 miles
north northeast of the islands will maintain a pressure gradient
tight enough to support moderate trade winds through the night. A
large west northwest swell that peaked this afternoon has lifted
significant seas up to around the 10 foot Small Craft Advisory
(SCA) criteria over those nearshore seas surrounding Kauai, the
Kauai and Kaiwi Channels, along with the windward Oahu and Maui
waters. An SCA is in effect for these waters until 6 AM HST Friday
morning. As this high sinks southeastward Friday onward, moderate
trades will veer more easterly and persist well into next week.
The approach of an early week cold front from the northwest may
hang up just west of the state as a low developments along it
northwest of the Hawaiian offshore waters. As this occurs, high
pressure moving in from the north will re-tighten the pressure
gradient upstream and over the island chain. This will strengthen
next week`s winds as they veer to more of a southeast direction.

A large, long period west-northwest (300-310 degree) swell has
recently peaked and will begin to subside from early Friday into
the weekend. As this swell gradually fades tonight, a High Surf
Warning will remain in effect for most of the smaller island`s
north and west-facing shores until 6 AM HST Friday. A High Surf
Advisory (HSA) is also in effect for the west-facing shores of Big
Island until 6 AM HST Friday. A northeast swell moving into our
nearshore windward waters Saturday may lift north and east-facing
shore surf across the state to near HSA levels.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 AM HST Friday for Niihau-Kauai Leeward-
Waianae Coast-Oahu North Shore-Maui Windward West-Kauai North-
Molokai Windward-Molokai North-Molokai West-Windward Haleakala.

High Surf Advisory from 6 AM to 6 PM HST Friday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai
North-Molokai Windward-Molokai North-Molokai West-Windward
Haleakala.

High Surf Advisory until 6 PM HST Friday for Kona-Kohala.

Small Craft Advisory until 6 AM HST Friday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters.


&&

$$


DISCUSSION...SWR
AVIATION...Bohlin
MARINE...Blood


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