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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 240135

Area Forecast Discussion
National Weather Service Honolulu HI
335 PM HST Fri Aug 23 2019

Moderate to breezy trades will continue through the weekend,
periodically delivering clouds and showers to windward areas while
most leeward areas remain mostly dry. Trade wind speeds may diminish
by the middle of next week.


As a weak surface trough N of the islands weakens and drifts NW over
the next 24-48 hours, surface high pressure will strengthen far N of
the area, and trade wind speeds will increase somewhat. The locally
breezy trade winds will continue through early next week, but are
expected to weaken Tuesday/Wednesday as the high weakens and a low
passes far N of the area. Winds may increase again by next weekend
as the low departs and the high consolidates far NE of the area.

A mid-level ridge will build over the area from the E the next
couple of days, supporting an increasingly stable island atmosphere.
With the ridge in place and no major sources of moisture expected
through the weekend, trade winds will periodically deliver clouds
and showers that will primarily dampen windward areas, while most
leeward areas remain dry. More significant moisture areas may become
embedded in the trade flow in about a week, but confidence in that
is close to zero.

Latest satellite images show an area of broken to overcast stable
and showery low clouds immediately upstream of the smaller islands,
associated with a weak trade wind disturbance that is sometimes
called a "screaming eagle". The presence of this feature is at least
partially responsible for today's lighter than expected trade winds.
Model guidance indicates that this feature will bring primarily
windward showers to the islands from Maui to Kauai through the
evening before moving W of the area by morning, with trades
increasing as it does so. Another slug of moisture passing S of the
Big Island may fuel some windward showers statewide Saturday night,
but nothing significant in the way of accumulation or coverage is


High pressure remains north of Hawaii with nothing to disrupt the
easterly trade winds. The wind speeds may be higher in some areas.
Expect the breezy conditions to continue through the weekend before
the pressure gradient loosens a bit. VFR conditions will dominate
most areas across the state with maybe a few passing, infrequent
MVFR conditions on the windward side of the mountains with clouds
and maybe a shower and lower visibility.

It will be breezy into this evening and again Saturday afternoon so
there is a chance for some pockets of low level turbulence south and
west of the mountains, and AIRMET TANGO . Other than that, no
AIRMETs are expected through this forecast period.


High pressure to the north will maintain moderate to locally strong
trades through the weekend. A Small Craft Advisory (SCA) is posted
through Sunday for the typically windy waters around Maui and the
Big Island. Another front is forecast to pass north of the state
next week with east trade winds weakening.

Only background south swell energy is expected over the weekend into
early next week. A larger, longer period southwest swell is expected
to arrive Tuesday and will likely peak Wednesday or Thursday near
advisory levels.

Small northwest swells will provide for above nil surf Saturday for
north and west facing shores before subsiding. Breezy trades will
continue to produce small choppy surf along east facing shores over
the next few days.


Small Craft Advisory until 6 PM 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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