Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Honolulu HI
1000 am HST Friday Apr 18 2014

Synopsis...
a trade wind weather pattern is expected over the next several days
thanks to high pressure north of the state. Clouds and passing
showers will favor windward and Mauka areas with a few showers
possible over some leeward locations.

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Discussion...
a 1025 mb surface high is centered far to the northeast of the state
with a ridge extending westward to another 1025 mb high far to the
northwest of the state. This places the islands in a moderate trade
wind environment. The high to the northeast is expected to weaken
while the high to the northwest strengthens a bit and moves eastward
over the weekend and on into early next week. As the high
strengthens to our north...we expect a slight uptick in trade winds
speeds during the Sunday and Monday time period. The high will
continue moving eastward to a position far to our northeast by the
middle of next week and weaken a bit as well. Thus trade winds will
likely drop back down to present levels.

Moisture embedded in the trades is providing for passing showers for
windward and Mauka areas with a few showers spreading over to select
leeward areas at times. An upper trough seen on satellite imagery
just to the southwest of the state has raised inversion levels a bit
allowing for slightly higher cloud development. A few windward and
Mauka gauges have received over an inch of rain over the past 12
hours. The upper trough is forecast to linger near the area over
the next several days. Thus showers will continue to favor windward
and Mauka areas and will be highly dependent on incoming moisture
availability.

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Aviation...
airmet Tango continues for low level turbulence to the Lee of the
islands. Upper level winds over the islands are sufficient enough to
continue an upper level turbulence airmet as well.

Clouds and showers are focused over windward and Mauka areas...which
at times will bring MVFR conditions to those areas. Otherwise...VFR
conditions are expected...with passing high clouds.

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Marine...
a Small Craft Advisory remains posted through Saturday afternoon for
the typically windy waters around Maui and The Big Island. This will
likely have to be extended into early next week as moderate to fresh
trade winds are expected to continue into the foreseeable future.

The current small northwest swell will continue to lower today.
Another small northwest swell is expected to fill in over the
weekend. Trade winds will continue to produce short period choppy
surf along east facing shores.

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

&&

$$

Synopsis/discussion/marine...Burke
aviation...M Ballard