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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 200136

Area Forecast Discussion
National Weather Service Honolulu HI
336 PM HST Sat Oct 19 2019

Trade winds will continue through the forecast period, thanks to
persistent high pressure to our north. Clouds and showers will
favor windward and mauka areas. Patchy high clouds will move over
the islands through early next week.


A 1027 mb high far northeast of the main Hawaiian Islands
continues to drive moderate to locally breezy trade winds across
local waters this afternoon. Satellite imagery shows scattered to
patchy broken low clouds moving across windward areas within trade
flow as well as thin high clouds moving west to east across the
entire state. Radar shows isolated to scattered showers associated
with the low clouds moving into windward areas. Isolated showers
are also noted across a few leeward areas as well.

Models show trade winds will prevail for the next week, with only
minor speed fluctuations expected. Moderate to locally breezy
trades will persist through tonight, then decrease Sunday through
Monday as a weakening cold front approaches from the northwest.
Trades are expected to increase again Monday night through
Wednesday as high pressure northeast of the state strengthens,
then trend down late next week as a new cold front approaches from
the northwest. Expect trade wind weather to continue for the next
7 days, with showers favoring windward and mauka areas along with
the occasional leeward spillover. Showers will be most common at
night and during the morning hours. High clouds associated with
a jet stream will continue to move overhead through the rest of
the weekend and into early next week.


Moderate easterly-northeasterly trade winds should continue
through the forecast period. Toward the end of Sunday, the trades
may shift a little to an easterly-southeasterly direction. We
have not had any reports of low-level turbulence so there will
probably not be a need for an AIRMET Tango as the winds are not
expected to increase much, if at all. The windward sides of the
islands will see passing MVFR conditions, especially during the
overnight hours. Will issue AIRMET Sierra for mountain obscuration
if necessary but so far with this persistent weather pattern, the
mountain obscuration has not been consistent enough to warrant an
AIRMET. VFR conditions are expected across the rest of the state.

No AIRMETs are currently in effect.


High pressure northeast of the state will maintain locally strong
easterly trade winds at least through tonight. A front will approach
the state from the north late tonight will cause winds to shift to
the east-southeast and weaken, especially over the western half of
the coastal waters, despite the front remaining north of the islands.
A Small Craft Advisory is in effect through tonight for the typically
windier areas near Maui County and the Big Island, but may need to
be extended through Sunday if winds are slower to drop off.

Surf is expected to remain below advisory levels through the forecast
period. The current combo north and northwest swell will continue
to gradually decline through the weekend. A somewhat larger northwest
swell could reach the islands late next week.

Near-shore buoys are also registering an increase in long-period,
south energy, so south facing shores should see a gradual rise in
surf through tonight as this small swell fills in. Surf should be
around the summer average over the weekend, before slowly dropping
off early next week.

The large fetch of fresh to strong trade winds near and east of
the state will maintain rough surf along east facing shores into
early next week. A slight decrease is possible Sunday as winds
briefly decrease, but choppy surf will quickly return as trades
restrengthen early next week.

See the Collaborative Nearshore Swell and Wind Forecast for Oahu
(SRDHFO) to get more details on surf and swell sources.


Small Craft Advisory until 6 AM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.




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

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It was last modified on: Wed, Dec 17 2014 - 1841 UTC
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