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Temp5.9 C
RH19 %
WindNE 9 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 261958

Area Forecast Discussion
National Weather Service Honolulu HI
958 AM HST Sat Sep 26 2020

Moderate trade winds will continue today, then weaken to gentle
speeds over the next few days. 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. This morning's satellite imagery is showing fair
weather cumulus clouds mainly over windward and mountain areas
with some light showers riding in with the trades. For rest of the
day today and tonight, we will continue to see passing showers
with a downward trend of winds and showers expected late tonight
into early Sunday morning.

As the high northeast of the state weakens, the trade winds will
become light enough for the development of sea breezes over select
leeward areas starting Sunday afternoon. 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 north to northeast
winds. Relatively dry weather conditions are expected with a few
light showers.

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 breeze and seabreeze weather regime with
afternoon clouds and showers developing over the interior areas
during the afternoon. 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.


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. AIRMET Sierra for mountain obscuration across Windward
Maui and the Big Island has been cancelled due to daytime cloud
lifting, but conditions are likely to return late tonight or early

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 trade winds


Moderate to fresh easterly trades will continue today, then 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