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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 311946

Area Forecast Discussion
National Weather Service Honolulu HI
946 AM HST Sun May 31 2020

Expect trade wind weather through the upcoming week with clouds
and showers favoring windward and mauka areas, and generally dry
weather expected over most leeward locations. An old frontal
boundary interacting with island terrain may produce increased
showers over starting around Monday night and continuing for a few


High pressure centered about 600 miles northwest of Oahu will
produce locally breezy and dry trade wind weather today. As with
any trade wind pattern, some windward and mauka showers will
still remain possible, but with a relatively dry atmosphere today,
showers will remain fairly light.

During the upcoming week, we will see remnants of an old frontal
boundary get caught up in the trade wind flow and that should
bring increasing showers to windward and mauka areas starting
around Monday night and lasting for a few days. Also, the remnants
of the frontal boundary will cause the dew points to increase,
which will likely make the weather feel slightly warmer than
normal. A drier trade wind pattern is expected to return during
the second half of the week.


Moderate to locally strong trade winds will persist through
twenty-four hours and beyond. Diurnal wind increases this
afternoon may result in gusts over 30 kt over summits and through
channeled areas of the Big Island and Maui this afternoon and
early evening. AIRMET Tango is in effect for the lee side of the
mountain ranges of Maui Molokai Lanai and the Big Island through
22z and is likely to be extended.

The air mass over the state remains mostly dry and mostly stable.
Shower activity will be limited and focused over island interiors
during the late afternoon and evening hours, then over north and
east facing slopes and coasts during the late night and morning
hours. Weak sea breezes are likely along Big Island Leeward
coast in the late afternoon and early evening hours.

Brief MVFR CIG and VIS are possible in isolated moderate showers.
Otherwise, VFR conditions will prevail all areas.


High pressure north of the area is providing for moderate to
locally windy trade winds across the area. A Small Craft Advisory
(SCA) is currently posted for the Alenuihaha Channel as an
overnight ASCAT pass indicated 25 kt winds there. The SCA will
remain up through tonight. The high is forecast to move off to a
position far northeast of the area on Monday resulting in a slight
decrease in trade wind speeds. The high is then forecast to build
back in to our north on Wednesday with trade winds increasing
once again.

Surf along south facing shores will remain slightly elevated
through Monday as a series of southerly swells move through the
area. A larger and longer period south swell is expected to fill
in Monday night, peak during the late Tuesday through Wednesday
time period, then lower gradually Thursday through Friday. A High
Surf Advisory is likely along south facing shores of all islands.
A smaller long period south swell is expected to arrive by next

A series of small north and northwest swells are on tap through
most of the week keeping surf above summertime flatness levels.
With the expected decrease in trade winds across the area, surf
will remain on the small side along east facing shores until the
trades pick up during the second half of the week.


Small Craft Advisory until 6 AM HST Monday for Alenuihaha




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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