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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 270157

Area Forecast Discussion
National Weather Service Honolulu HI
357 PM HST Sat Sep 26 2020

Trade winds will continue to weaken overnight, and will drop down
to light to moderate speeds on Sunday. Background light trade
wind flow will persist through Tuesday with winds weak enough for
localized sea breeze development. A plume of moisture is expected
late Sunday into Sunday night and will likely bring some scattered
showers. Winds are expected to become light and variable by
midweek with a land/sea breeze weather regime expected during the
second half of the week.


High pressure northeast of the state will maintain moderate trades
through tonight with a decrease in wind speeds expected on Sunday
into early next week as the high to the northeast weakens. For
Sunday, light to moderate trade winds are expected with winds
light enough for localized sea breezes over leeward areas. Sunday
morning should start off sunny for most areas, but an increase of
clouds and showers are expected in the late afternoon and evening,
as a pocket of moisture moves in from the east. This moisture
will linger across the state through Monday morning with scattered
showers expected over windward and mountain areas and some
isolated showers over leeward areas.

For Monday afternoon and Tuesday, we should see a drier airmass
move in across the state with background northeast winds.
Relatively dry weather conditions are expected with a few light

For the second half of next week, we will see the winds weaken
further with light and variable winds expected across the state.
We will see a land/sea breeze weather regime with afternoon
clouds and showers developing over the interior areas during the
afternoons. As the land breeze begins to develop during the
evening, these clouds and showers will begin to move towards the
coast and move offshore by late night. The main uncertainty in the
extended forecast is the intensity of the afternoon showers. Some
guidance is indicating some tropical moisture moving near the
state, and if this were to materialize we could potentially see
some brief downpours during the afternoons.


High pressure far northeast of the state will maintain light to
locally moderate trade wind flow across the Main Hawaiian
Islands through twenty hours and beyond. Low topped clouds and
scattered light showers will favor north and east facing slopes
and coasts. Isolated MVFR conditions are to be expected in
showers, otherwise VFR conditions will prevail all areas.

AIRMET Tango remains in effect for moderate low-level turbulence
over and downwind of the terrain of all islands. Conditions are
expected to improve later today or tonight as the summit level
winds ease.


Moderate to fresh easterly trades will begin to trend down
tonight. Localized land and sea breezes near the coasts could
begin to develop as early as Sunday, with that pattern continuing
for the next several days as the ridge weakens in response to a
series of fronts passing to the north.

Surf along north facing shores will slowly lower through the
weekend, but the active pattern across the northern Pacific is
forecast to continue into next week as the jet stream amplifies
and drives back-to-back systems southeastward across the Date
Line. The first of these swells would arrive Wednesday and peak
Thursday, with surf nearing advisory level, while the second
arrives Friday.

Surf along south facing shores will remain up through the weekend
as a long-period south-southwest swell fills in today, with heights
nearing advisory level (8 ft faces) by Sunday as it peaks. A gradual
downward trend is expected late Sunday into early next week. For
the long range, the active trend is expected to continue down
south around New Zealand within Hawaii's swell window. If this
evolves as predicted, expect another decent south swell by the end
of the first week in October.

Surf along east facing shores will remain small through the
weekend due to the slackening trades. However, a small easterly
swell from former tropical cyclone Lowell in the eastern Pacific
can't be ruled out early next week, especially for the eastern end
of the state.

The large daily tide cycles will gradually trend down toward the
monthly minimum each day into the first week of October.






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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