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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 230139

Area Forecast Discussion
National Weather Service Honolulu HI
339 PM HST Thu Aug 22 2019

Expect a typical trade wind weather pattern through the weekend,
with clouds and showers favoring windward and mauka areas. Warm
and humid conditions are forecast Tuesday through midweek as
wind speeds trend down into the light and variable range.


An upper low and a dissipating surface trough north through
northeast of the islands puts a dent in the subtropical ridge.
That said, locally breezy trade winds continue across local waters
this afternoon. Satellite loop shows clouds focusing across
windward and mauka areas of the islands, with rather sparse cloud
cover upwind from the islands. Radar shows isolated to scattered
light showers, mainly across windward areas.

Models show trade winds will remain locally breezy as the upper
low and dissipating surface trough pass westward and the ridge
rebuilds. The current weather pattern will prevail with clouds
and showers favoring windward and mauka areas. An increase in
shower coverage is possible late Saturday into Sunday as a pocket
of higher moisture moves through from east to west.

After the weekend, models show a weakness developing within the
ridge as a broad upper trough and surface front pass to the north.
The pressure gradient will weaken over the state, possibly
allowing a land and sea breeze regime to develop Tuesday through
midweek. If this scenario evolves, clouds and showers will favor
interior areas through the afternoon and evening hours.


A ridge N of the area will maintain locally strong E flow over
the main Hawaiian Islands through tomorrow.

VFR conditions will prevail through the night, but ISOL MVFR
ceilings or visibilities are possible over E sections of the
islands. Satellite loops show an area of showery low clouds a few
hundred miles east of the Big Island of Hawaii moving W toward
the islands. This cloud area may produce more widespread MVFR
conditions when it reaches the islands tomorrow, especially over
the E side of the Big Island.


High pressure to the north will maintain mostly fresh trades
through Friday. Thus, the Small Craft Advisory (SCA) has been
extended through Friday for the typically windy waters around Maui
and the Big Island. A trough approaching from the north will
briefly ease the trade winds Friday night to below SCA levels. A
new high building northeast of the islands will then strengthen
winds back to moderate and locally strong levels over the weekend,
with SCAs likely being required once again for the windier marine

A south swell will continue to decline through Friday. A series
of small long-period south and southwest swells will maintain
average surf along south shores Sunday through early next week. A
larger southwest swell may arrive Tuesday and remain through the

Small northwest swells will linger over the next few days
providing some out of season surf along north facing shores.
Breezy trades will continue to produce small choppy surf along
east facing shores over the next few days. An increase in wind
swell is expected late in the weekend as trades strengthen locally
and upstream of the state.


Small Craft Advisory until 6 PM HST Friday 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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