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Area forecast discussion 
National Weather Service Honolulu HI
406 PM HST Thu Oct 27 2016

breezy trade winds will continue through the weekend, then ease a
bit next week. Passing low clouds and showers will affect mainly
windward and mountain areas. An area of moisture to the northeast
will enhance showers late tonight into Friday, and may affect
some leeward areas as well. An upper level trough will move over
the state this weekend, resulting in heavier showers and wet trade
wind weather into early next week.


water vapor imagery shows a weak mid-level ridge over the state,
with a trough to the northwest. At the surface, high pressure is
located far north of the state, with a front in between around
33n. 00z soundings from Lihue and Hilo show inversions of 7-8kft.
Precipitable waters range from 1.05 at Lihue to 1.29 at Hilo,
which are drier than normal for this time of year. Afternoon mimic
total precipitable water imagery shows higher moisture from Maui
County eastward, extending upstream across the eastern offshore

Much of the area has stayed cloudy today, greatest across windward
sections but with occasional clouds and showers passing leeward as
well, especially from Oahu to Maui. Additional moisture just
entering the windward coastal waters will enhance showers
tonight/Friday. Forecast soundings/cross sections show a minor
surge in moisture depth, but with the inversion remaining in
place. We will also see a surge in trade wind speeds as well. The
high to the north will move southeast and weaken slightly.
However, the front between US and the high will dissipate,
bringing US more under the direct influence of the high and lead
to the stronger wind speeds.

The upper trough currently to the northwest will amplify and dig
across the state this weekend, then linger nearby through Monday.
Falling mid-level temperatures will help to erode the inversion
and destabilize the atmosphere. Showers will be more active this
weekend, and with the strong trade winds they will more frequently
spread leeward as well.

The GFS and European model (ecmwf) are pretty similar with the overall pattern near
the islands through the forecast period. By Tuesday, a strong
mid-level ridge builds across the state from the west,
reestablishing the inversion and returning US to a more typical
trade wind weather pattern. Through a series of surface highs and
fronts passing far north of the state, the subtropical ridge
gradually shifts southward through next week. Late in the week the
ridge may approach the far northern offshore waters, with trade
wind speeds across the islands dropping to more moderate levels.


VFR conditions prevail at most taf sites but there has been some
brief MVFR conditions at phny and phmk due to low clouds and
rain showers. There will likely be some brief MVFR conditions early
tonight over windward slopes with the possibility of tempo MVFR
later tonight as moisture riding in on the trades interacts with
island terrain.

Airmet Tango is currently posted for low level turb south and west of
mountain ranges due to breezy trade winds. We can expect these
conditions to continue tonight and Friday.


the morning ascat pass covered the area from Oahu to The Big
Island and supports small craft conditions for most areas. High
resolution model guidance shows a greater surge in trade winds
tonight, and we will begin the expanded small craft for all waters
with this package.

A series of small to moderate north and northwest swells will
fill in over the weekend and again toward the middle of next week,
but surf heights are expected to remain below advisory levels. A
long period east swell is possible this weekend from the distant
Hurricane Seymour in the eastern Pacific. Furthermore, east facing
shores will see an increase in rough and choppy surf under the
strengthening trades, possibly approaching advisory level in the
next few days.


Hfo watches/warnings/advisories...
Small Craft Advisory until 6 PM HST Sunday for Oahu windward
waters-Oahu leeward waters-Kaiwi Channel-Maalaea Bay-Pailolo
Channel-Alenuihaha Channel-Big Island leeward waters-Big Island
southeast waters.

Small Craft Advisory until 6 PM HST Sunday for Kauai northwest
waters-Kauai windward waters-Kauai leeward waters-Kauai Channel-
Maui County windward waters-Maui County leeward waters-Big
Island windward waters.




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