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RH76 %
WindWSW 16 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

163
FXHW60 PHFO 160705
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
905 PM HST Wed Aug 15 2018

.SYNOPSIS...
A high will remain far northeast of the area through early next
week. A far northwest of the area will move east to a position
north of the islands by the middle of next week. Tropical moisture
will move west across the area though the weekend. Drier air will
move over the islands on Monday. Tropical Storm Lane will likely
strengthen to a hurricane and move into the central Pacific over
the weekend. It is too soon to know if Lane will directly affect
the Hawaiian Islands.

&&

.DISCUSSION...
The surface analysis at 800 PM shows a 1026mb surface high around
1700 miles northeast of the islands near 43N 142W. The high is
forecast to move northeast slowly through early next week. This
distant high will maintain gentle to moderate easterly trade winds
over the islands through early next week.

An area of moist air associated with a trough in the lower
atmosphere has been moving west across the islands. A trough
higher in the atmosphere northwest of the islands is making the
atmosphere somewhat unstable. The combination of moisture and
instability will keep showers active for the next few days. Since
trade winds will continue, showers will be focused over mainly
windward areas but cloud will build high enough to spill over to
some leeward areas. Thunderstorms will be possible over the Big
Island slopes during the afternoons and evenings. A new area of
tropical moisture will spread over the islands during the weekend
and enhance showers even more.

Tropical Storm Lane, now far southeast of the islands, is forecast
to strengthen to a major hurricane and move into the central
Pacific over the weekend. It is too soon to know if Lane will
directly impact the islands. An indirect impact associated with
Lane may be seen early next week as drier air associated with
subsidence ahead of the hurricane spreads over the islands on
Monday.

&&

.AVIATION...
Light to locally moderate trade wind speeds are expected through
Thursday, supported by a surface high to the distant northeast.
An area of moisture embedded in the trade wind flow lies over
windward waters from Oahu to the Big Island, with some of this
moisture moving ashore over windward areas. With a nearby upper-
level trough providing instability, showers are more active than
usual, and a few of showers are locally heavy, leading to areas of
MVFR VIS/CIG with isolated areas of IFR VIS/CIG. PHTO will be the
terminal most likely to be impacted. AIRMET Sierra for mountain
obscuration is posted for windward Big Island where low clouds and
showers have persisted.

Little overall change is expected through Thursday, with the light
trade winds keeping most clouds and showers focused over windward
slopes and coasts. However, trade winds will be sufficiently
light to allow afternoon leeward sea breezes to drive the
formation of some clouds and a few showers, some of which may be
locally heavy and/or develop into thunderstorms, mainly over the
interior portions and slopes of the Big Island.

&&

.MARINE...
Light to moderate trade winds are expected to continue through the
weekend. Winds are expected to remain below Small Craft Advisory
levels, with an uptick in winds possible early next week. Shower
activity is expected to increase this weekend, particularly over
the windward waters as tropical moisture moves in from the east.

No significant swells are expected over the next several days, so
expect surf to remain small on all shores. A small south-southeast
swell is expected to fill in Thursday, peak Friday and hold
through Saturday at heights below the summer average. We will
continue to monitor the development of tropical cyclone Lane,
which is currently located in the eastern Pacific. Lane may bring
an easterly swell to the coastal waters as early as Monday of
next week.

See the latest Collaborative Surf Discussion for more details on
surf and swell.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
DISCUSSION...Donaldson
AVIATION...Birchard
MARINE...Kino

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