Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 230215
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
415 PM HST Sun Jan 22 2017

.SYNOPSIS...
High pressure northeast of the state will begin to lose its
influence on the area tonight as a cold front approaches from the
northwest. This will allow the windy trades to gradually ease from
west to east across the island chain. The front will pass by well
to the north of the state Monday and Monday night, further easing
the trades and allowing for localized sea and land breezes.
Moderate trade winds will then rebuild across the island chain
Tuesday through Thursday as high pressure sets up to the northeast
of the state. A cold front will approach from the northwest late
in the work week and move through the island chain next weekend.
Showers will favor windward and mauka areas through the work week,
with more widespread shower activity expected next weekend as the
cold front pushes down the island chain.

&&

.DISCUSSION...
Currently at the surface, a 1031 mb high is centered around 825
miles to the northeast of Honolulu, with a weakening cold front
around 80 miles to the south of South Point on the Big Island.
Although winds have eased a bit since early this morning, windy
conditions remain in place across the island chain this afternoon.
Visible satellite imagery shows mostly cloudy skies in place in
windward areas, with partly cloudy conditions across most leeward
locales. Meanwhile, radar imagery shows scattered showers moving
into windward areas, with some light showers or sprinkles reaching
leeward areas from time to time. Main short term concern for
tonight revolves around wind headlines.

Tonight,
The strong trades are expected to ease overnight as high pressure
northeast of the state begins to lose its influence on the island
chain. Winds are expected to drop below advisory levels early this
evening across Oahu and Kauai, so we expect to allow the Wind
Advisory to expire here at 6 pm. Across Maui County and the Big
Island, the easing of the trades will be a bit delayed, so we have
extended the Wind Advisory until 10 pm here. The High Wind Warning
has been cancelled. As for sensible weather details, the trades
will continue to focus showers over windward and mauka areas
overnight, with windward sections of the Big Island and Maui
expected to see the most persistent shower activity. Isolated to
scattered light showers or mist will reach leeward areas of the
smaller islands from time to time as well.

Monday and Monday night,
High pressure will shift eastward and further away from the state
as a cold front passes by well to the north of the island chain.
This will weaken the trade wind flow across the state, with
localized sea breezes and land breezes expected in some areas. As
for sensible weather details, showers will focus primarily over
windward and mauka areas through the period. Some heavier showers
may affect windward sections of Maui and the Big Island however,
as an upper level disturbance moves overhead and the remnant
moisture from the old front lifts northward into these areas.

Tuesday through next Sunday,
Model guidance is in good agreement, showing high pressure
rebuilding north of the state Tuesday through Thursday, allowing
moderate trade winds to become re-established across the island
chain. The trades will then diminish Thursday night through
Saturday as a cold front approaches from the northwest. The cold
front is expected to push into Kauai by late Saturday afternoon
and down the island chain Saturday night and Sunday. Clouds and
showers will favor windward and mauka areas through the period.
The coverage of showers is expected to remain greatest Tuesday and
Tuesday night particularly over windward sections of Maui and the
Big Island where lingering deep moisture and lower upper level
heights will reside. Drier more stable conditions are expected
statewide Wednesday through Friday night as deep layer ridging
builds over the area. Showers are then expected to increase over
the weekend as the cold front pushes down the island chain.

&&

.AVIATION...
A remnant cold front lingers around 80 miles south of the Big
Island this afternoon. A high pressure center roughly 825 miles
northeast of Honolulu will continue to move eastward away from the
state resulting in weaker trade winds during the overnight hours.
An upper level trough moving eastward across the islands will
bring a period of cirrus clouds to all islands this evening.

Mostly VFR conditions are forecast through the overnight hours
with scattered MVFR mainly along windward areas of all islands
and isolated MVFR elsewhere.

AIRMET SIERRA for mountain obscuration over northern and eastern
slopes of Maui and the Big Island remains in effect.

AIRMET TANGO for low level moderate and isolated severe
turbulence south and west of all the Hawaiian Islands remains in
effect. Wind speeds will weaken tonight, decreasing turbulence
activity and likely ending this Airmet.

&&

.MARINE...
Generally treacherous conditions continue across the Hawaiian
coastal waters this afternoon.

As strong trade winds have gradually declined from their peak,
have trimmed back the areal extent of the gale warning in the
coastal waters. Expecting these windier waters, South and
Southeast of Oahu, surrounding Maui County and the Big Island, to
continue to experience gale force winds for the next few hours.
Some of these areas will drop out of the gale area after 6 pm this
evening, please refer to the latest Marine Weather Message,
MWWHFO, for further details. The rest of the coastal waters zones
remain covered by a small craft advisory, which covers both the
strong trade winds and the 10 plus foot choppy, wind driven seas
which will pose a continuing hazard into at least early Monday.
Windward waters and the channels will hold the most hazardous
conditions for small craft through the period, and these areas
will experience the worst conditions for the longest period. The
small craft advisory will likely need to be extended in some areas
beyond Monday.

Short period trade wind swell along the east facing shores will
continue to bring high surf advisory level surf for east facing
shores continuing through Monday afternoon.

A large northwest swell will likely produce surf well above the
advisory threshold along north and west facing shores of the
smaller islands from Tuesday through Thursday morning. Another
large northwest swell may produce advisory-level surf along north
and west facing shores of the smaller islands starting Friday
night and continuing into next weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM HST this evening for Niihau-Kauai-Oahu.

High Surf Advisory until midnight HST tonight for Niihau-Lanai.

High Surf Advisory until 6 PM HST Monday for Kauai Windward-Oahu
Koolau-Olomana-Molokai Windward-Maui Windward West-Windward
Haleakala-Big Island North and East.

Wind Advisory until 10 PM HST this evening for Molokai-Lanai-
Kahoolawe-Maui Windward West-Maui Leeward West-Maui Central
Valley-Windward Haleakala-Leeward Haleakala-Kona-South Big
Island-Big Island North and East-Kohala-Big Island Interior.

Gale Warning until midnight HST tonight for Maalaea Bay-Pailolo
Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters.

Small Craft Advisory until 6 PM HST Monday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Big Island Windward Waters.

Gale Warning until 6 PM HST this evening for Oahu Leeward Waters-
Kaiwi Channel-Maui County Windward Waters-Maui County Leeward
Waters.

&&

$$

DISCUSSION...Jelsema
AVIATION...Bohlin
MARINE...Brenchley


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