High Surf in Hawaii, February 4 to 6, 2021

Area Forecast Discussion
National Weather Service Honolulu HI
855 PM HST Wed Feb 3 2021

.SYNOPSIS...
A weakening cold front will move through Maui County tonight, then
make a slow exit east of the Big Island on Thursday. Showers will
be most prevalent along the front, with much drier and cooler
conditions building in following the frontal passage. Cool
conditions, light winds, and a few light passing showers mainly
affecting north and west facing slopes and coasts are then
expected Friday through the weekend. Another weather system is
expected to approach the state early next week, possibly bringing
another round of widespread rainfall to the island chain.

&&

.DISCUSSION...
Currently at the surface, the cold front which moved through
Kauai and Oahu earlier today, is entering Maui County this
evening. Meanwhile, around 1200 miles west-northwest of the
islands, a 1024 mb high is building in. Breezy northwesterly winds
have developed behind the front, while breezy south to
southwesterly winds prevail out ahead of it. Infrared satellite
imagery shows mostly cloudy skies over Maui County and the Big
Island. Meanwhile, partly to mostly cloudy conditions are present
over Kauai and Oahu, with the greatest cloud coverage over the
northwest sections of each island due to the northwesterly winds.
Radar imagery shows showers moving through Maui County and the Big
Island in advance of the front, while post-frontal showers are
focused mainly over northwest coasts and slopes of Kauai and Oahu.
Main short term concerns revolve around ongoing headlines
associated with the front.

The cold front will continue to push eastward through Maui County
and into the Big Island tonight, likely pushing east of the Big
Island on Thursday. Breezy northwesterly winds behind the front
will begin to ease to moderate levels on Thursday, then lower
further Thursday night as high pressure begins to nose in from the
west. Winds are expected to become light and variable Friday
through the weekend, as the axis of high pressure settles right
over the islands. This is expected to result in daytime sea
breezes and overnight land breezes statewide. Model solutions
appear to be converging on a new cold front approaching from the
west Monday, then moving southeastward through the island chain
Monday night and Tuesday. This would bring breezy southwesterly
winds in advance of the front, with breezy northwesterly winds
building in behind it for Tuesday night and next Wednesday.

As for the remaining forecast details, showers and isolated
thunderstorms will remain possible in advance of the front
tonight, while much drier air continues to move in behind the
front, limiting showers primarily to north and west facing slopes
and coasts. Shower coverage will likely remain a bit higher over
the Big Island Thursday and Thursday night as the weakening front
and associated deep moisture makes a slow exit to the east.
Meanwhile fairly dry conditions are expected to prevail across
the smaller islands, although a few showers may move into north
and west facing slopes and coasts due to the cool west-
northwesterly boundary layer flow. Fairly dry weather is then
expected to persist statewide Friday through Sunday night, with
a few showers possible in north and west facing slopes and coasts
due to the prevailing west-northwest boundary layer flow, and a
few interior and mauka showers possible in the afternoon hours
aided by sea breezes. Rain chances then appear to increase late
Monday through Tuesday in association with then next cold front
forecast to move through the islands. Drier weather appears to
return by the middle of next week as high pressure noses in from
the west.

As for ongoing headlines...
Winds have dropped below advisory levels over the lower
elevations of the Big Island, so the Wind Advisory has been
cancelled here.

Moisture remains deep enough and temperatures cold enough to
support wintry weather over the Big Island summits and the
Haleakala summit tonight. A Winter Weather Advisory remains in
effect for the Big Island summits through 6 AM Thursday and for
the Haleakala Summit through 10 AM Thursday.

&&

.AVIATION...
A weakening front moving toward the Big Island is bringing layered
clouds with embedded heavy showers from Maui County to the Big
Island. Expect widespread MVFR with isolated IFR and LIFR as the
front moves east tonight. Some strong surface winds will remain
tonight over and around terrain. Behind the front some low topped
showers are expected to bring some mountain obscuration to north
and west facing slopes.

AIRMET Sierra for mountain obscuration will be modified through
the night as conditions warrant.

AIRMET Tango for moderate mid-level turbulence remains in effect
for the entire area.

Light rime icing will continue for layered clouds near the Big
Island.

&&

.MARINE...
A weakening front is over the eastern part of the state this early
evening and moving steadily east. Some gusty southwest and west
winds and possible isolated thunderstorms remain a threat through
the late evening for portions of Maui County waters and waters
around the Big Island.

For building seas associated with an incoming large northwest
swell, a Small Craft Advisory (SCA) has been posted for most coastal
waters, with seas rising from west to east across the island
chain over the next 12 to 24 hours.

The new, large northwest swell will likely lead to High Surf
Warning conditions beginning Thursday for north- and west-facing
shores of most of the islands from Maui westward. With the swell
orientation being west-northwest initially, there is a chance
some of this energy may affect west-facing shores of the Big
Island by later Thursday into Friday. The swell will begin to
gradually subside beginning Friday over the western islands and
Friday night elsewhere. The latest model run, however, shows
northwest swell energy remaining somewhat elevated through the
weekend.

No significant swells are expected elsewhere through early next
week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning from 6 AM Thursday to 6 AM HST Friday for
Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-Oahu North
Shore-Oahu Koolau.

Winter Weather Advisory until 6 AM HST Thursday for Big Island
Summits.

Winter Weather Advisory until 10 AM HST Thursday for Haleakala
Summit.

Small Craft Advisory from 6 AM Thursday to 6 AM HST Friday for
Maui County Leeward Waters-Alenuihaha Channel-Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Waters.

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

&&

DISCUSSION...Jelsema
AVIATION...Morrison
MARINE...Kinel