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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 241343
Area Forecast Discussion
National Weather Service Honolulu HI
343 AM HST Sat Aug 24 2019
A high north of the area will move northeast slowly and maintain locally
breezy easterly trade winds through the weekend. An area of moisture
southeast of the islands may spread over the area today and increase
showers over mainly the Big Island. Winds will weaken next week
as the high moves farther away and rainfall will likely be sparse.
The latest surface analysis shows a 1025 mb surface high about
1000 miles north of the area near 38N153W. The pressure gradient
south of the high is maintaining locally breezy easterly trade
winds over the islands.
An area of showery low clouds that moved over the islands last
night is moving away to the west of Kauai. As of 3 AM, satellite
loops show mostly clear skies over leeward areas and partly cloudy
skies over windward areas. Radars show only isolated light
showers upstream to the east of the islands. The global models
show an area of increased moisture moving toward the islands from
the southeast that may produce an increase in showers, especially
for the windward side of the Big Island, later today.
The global models are in good agreement showing the high north of
the area moving northeast slowly. As the high moves away, the
pressure gradient over the islands will become looser and the
trade winds will weaken. Wind speeds will likely become gentle to
moderate by Tuesday and remain at that strength through the rest
of the week. Moisture will remain rather low and ridging aloft
will keep the atmosphere stable so rainfall will be sparse through
A ridge north of the area will maintain breezy trade winds through
the weekend. Enhanced overnight shower activity has diminished
across the state as a weak low level trough moves west of Kauai.
AIRMET Tango is in effect for low level Moderate Turbulence south
through west of all islands. AIRMET Tango will likely remain in
effect through the weekend.
High pressure to the north will maintain breezy trades through
early next week. The high shifts north after Sunday causing the
pressure gradient around the islands to loosen, leading to lighter
trades towards the middle of next week. A Small Craft Advisory
(SCA) is currently in effect through Sunday for the typical windy
waters around Maui and the Big Island. But another surge in the
trades will likely expand the SCA to waters beyond its common
areas. This will likely go into effect later today or tonight.
The SCA, which good until 6 pm HST Sunday, may need to be extended
as well. On Monday, the trades will begin trending lighter
leading to the scaling back of the SCA.
A surface trough is about to clear the offshore waters west
through northwest of Kauai.
A large, long period southwest swell is expected to arrive
Tuesday and peak Wednesday or Thursday. Otherwise, the surf along
the south facing shores will be small. A northwest swell will
maintain small surf along the north and west facing shores over
the weekend. Meanwhile, the stronger trades will result in a
slight rise in the surf along the east facing shores. This trade
wind swell will trend lower by the middle of next week as the
trades become weaker, resulting in smaller surf. The strong trades
will cause rough and choppy water conditions, especially along
east facing shores over the weekend and into early next week.
Small Craft Advisory until 6 PM Sunday for Maalaea Bay, the
Pailolo and Alenuihaha Channels and waters south of the Big
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
Send comments to: Ryan Lyman