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Temp4.8 C
RH9 %
WindSSW 17 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

784
FXHW60 PHFO 231416
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
416 AM HST Thu Jan 23 2020

.SYNOPSIS...
Variable winds in a stable land and sea breeze weather pattern
will continue over most of the islands through Friday afternoon.
Expect low clouds developing with isolated light interior showers
possible each afternoon followed by overnight clearing across most
islands. One exception will occur over the southeast slopes of
the Big Island where a slight increase in clouds and showers
remains in the forecast through Friday. A weak front stalling
near Kauai on Friday evening will increase clouds and showers
over the Garden Isle through Saturday. Moderate trade winds will
return from Friday afternoon through the weekend along with slight
increases to windward and mountain showers. Winds will decrease
and veer southeasterly in a dry land and sea breeze pattern for
the first half of next week.

&&

.DISCUSSION...
Satellite imagery this morning shows a small band of fairly
stable low clouds and light rain just west of Kauai and Niihau.
Clouds and a few showers from this band may reach the western
slopes of Kauai through the morning hours. Another band of low
clouds associated with a weak low level disturbance will move into
the eastern slopes of the Big Island later today with a slight
increase to cloud cover expected along east and southeastern
slopes. Elsewhere mostly clear skies prevail under a stable high
pressure ridge pattern. Light and variable winds will continue
through the end of the week allowing local scale land and sea
breezes to continue. Dry moisture levels in the atmosphere will
produce cooler than normal low temperatures each night.

Friday through Sunday, the weather pattern changes a bit as a
weakening cold front moves into Kauai and Niihau. This front will
reach Kauai by Friday evening just as the forward motion along
the frontal band stalls out. Expect increasing clouds and showers
for both islands from Friday into Saturday. Trade winds will bleed
out ahead of the stalling frontal band with trades slowly
spreading eastward to all islands through Saturday morning. Clouds
and isolated to scattered showers will also return over windward
and mauka areas with these moderate trades lasting through the
weekend. East to southeast trade winds on Sunday will push the
clouds and showers along the remnant frontal boundary towards the
northwest away from Kauai County with improving weather conditions
in the forecast from Saturday night onward.

Monday through Wednesday, trade winds will veer towards the
southeast direction with a subtropical ridge axis anchored roughly
400 miles north of the island chain. Light southeasterly winds
will allow a return to land and sea breezes over the islands with
a slight increase to clouds and showers along the southeastern
slopes of the Big Island. This drier weather pattern will bring
sunny skies back to the islands through the middle of next week.
Additional high clouds moving into the region next week will
improve sunrise and sunset colors from Wednesday onward.

&&

.AVIATION...
A surface high pressure ridge axis will remain stagnant over the
state for the forecast period and bring a light and variable flow
pattern. This morning, relatively dry air across the region
should keep precipitation chances to a minimum. By this
afternoon, however, expect weak sea breeze development along
coastal areas and a slight chance of showers over island
interiors. Elsewhere, light winds and dry conditions will prevail.

&&

.MARINE...
Light and variable winds will continue through early Friday, then
shift out of the north to northeast and increase into the moderate
to fresh category late Friday as a front passes north of the area.
Fresh to locally strong easterly trades are expected for a brief
period over the weekend before trending back down by early next week
as a series of fronts pass to the north. Although seas may briefly
drop below the Small Craft Advisory (SCA) level (10 ft) Friday as
the large northwest swell subsides, advisory-level conditions
will return Friday night through the weekend due to a combination
of winds and seas.

Surf along north and west facing shores will remain up through next
week due a series of large northwest swells evolving from the
progressive pattern over the northern Pacific. The current swell
building down the island chain is peaking this morning at the
Hanalei and Waimea nearshore PacIOOS buoys, with a peak expected
over the Maui waters by or around daybreak. Although a gradual
downward trend will begin later today, surf will hold above
warning levels for exposed north and west facing shores. The
downward trend will be short-lived due to another large northwest
swell arriving Friday night into Saturday from a large area of
gale- to storm-force winds that has setup within the 300-320
directional band relative to the islands over the northwest
Pacific. Surf will respond and return to warning levels Saturday
through Sunday. As this swell eases into early next week,
advisory-level surf may hold through late Monday before dropping
below on Tuesday. Another large northwest swell will be possible
by Wednesday as a gale develops over the far northwest Pacific
this weekend.

Surf along exposed east facing shores will remain small through the
period due to the lack of persistent trades locally and upstream
across the eastern Pacific.

Surf along south facing shores will remain small through next week.
A couple of background south swells expected over the weekend and
next Tuesday should be enough to keep things from going flat.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 AM HST Friday for Niihau-Kauai
Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu
Koolau-Olomana-Molokai-Maui Windward West-Maui Central Valley-
Windward Haleakala-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-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Big Island Windward Waters-Big Island
Leeward Waters-Big Island Southeast Waters.

&&

$$

DISCUSSION...Bohlin
AVIATION...JT
MARINE...Gibbs

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office