Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
830 PM HST Friday Aug 22 2014
high pressure north of the state will keep trade winds blowing
across the islands and local waters through the forecast period.
Clouds and showers will favor windward and Mauka areas. Winds will
become lighter next week as the high pressure to our north weakens.
a 1030 mb high near 42n144w...far north northeast of the main
Hawaiian islands...has an associated ridge extending southwest
through 30n170w and 25n180w. The pressure gradient between this
ridge and equatorial low pressure is sufficiently steep to keep 20
to 25 miles per hour northeast trade winds blowing across local waters this
evening. Satellite loop shows loose patches of broken low clouds are
embedded within trade wind flow over and upwind from the islands.
One of these broken low cloud patches lies across windward Big
Island slopes and is poised to reach Maui within a few hours. Radar
shows scattered moderate showers within this cloud area...but only
isolated light showers farther to the west. We expect a continued
trade wind weather pattern for the forecast period...with clouds and
showers favoring windward and Mauka areas.
Models show the high to our north northeast will weaken and move
southwest by early next week. While the overall position of the
ridge will be unchanged...the weakened high will cause the pressure
gradient to slacken across the islands...resulting in decreased
trade winds. The current forecast keeps at least light trade flow
through the forecast period...but local land and sea breezes may
develop across leeward areas late next week and toward next weekend.
areas of showery low clouds embedded in the trade wind flow will
bring brief MVFR visible/ceiling to windward slopes...coasts and adjacent
waters...otherwise VFR conditions will prevail through early
Saturday morning. Some of the rain showers will occasionally spread leeward
on the smaller islands. No airmets are in effect.
a Small Craft Advisory is in effect for the usual windy waters
around Maui County and The Big Island through tonight. Winds are
expected to drop off just a bit over the weekend and on into early
A high surf advisory remains in effect for south facing shores. This
swell will gradually lower tonight and Saturday. A series of
moderate south swell are expected over the next several days...with
a slightly larger swell possible Wednesday and Thursday. The
combination of easterly trade winds and swell from distant tropical
cyclones will continue to produce moderate surf along east facing
shores through the middle of next week.
high surf advisory until 6 am HST Saturday for Niihau-Kauai
windward-Kauai leeward-Oahu South Shore-Waianae coast-Molokai
leeward-Lanai-Kahoolawe-Maui leeward west-Maui Central Valley-
leeward Haleakala-Kona-south Big Island-kohala.
Small Craft Advisory until 6 am HST Saturday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island southeast waters.