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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 040621

Area Forecast Discussion
National Weather Service Honolulu HI
821 PM HST Mon Aug 3 2020

Moderate to breezy trade winds will continue through the week, and
may get a little stronger by the weekend. The trade winds will
deliver passing low clouds and showers that will primarily focus
over windward areas, with a few showers occasionally spreading
leeward on the smaller islands. Increased moisture and a passing
disturbance aloft are expected to bring an uptick in showers from
Tuesday night into Friday.


In summary, trade winds will prevail for the foreseeable future,
delivering low clouds and showers to windward areas that will
occasionally spread leeward. An increase in moisture will likely
bring greater low cloud and shower coverage from Tuesday night into
Friday, favoring windward areas, and most active during nights and
mornings. The trade-wind-supplying high to the distant N and NE is
expected to bring stronger trades over the weekend as low-level
moisture diminishes slightly. A weak trough aloft to the W of the
islands will bring periods of high clouds that are not expected to
be very thick, but bring the potential for colorful sunrises/sunsets.

Moderate to breezy trade winds and a fairly typical weather pattern
will remain in place through Tuesday, supplied by broad surface high
pressure far north of the state. A mid-level ridge overhead is
maintaining stable conditions with an inversion based around 7,000
ft, and precipitable water (PWAT) is running below August normal at
about 0.9". A few brief windward showers are expected in the short
term, and typical windward rainfall is expected over the W half of
the state. A narrow slot of drier air is expected to favor
suppressed shower activity on the Big Island and Maui overnight,
followed by an increase in showers on the Big Island as an area of
moisture largely skirts by to the S on Tuesday.

An increase in shower coverage appears likely from Tuesday night
into Friday; based on the consistency in forecast guidance in
advecting an area of higher PWAT that is currently near 150W. In
addition, a mid-level trough will slowly move over the state from
the E, destabilizing the lower atmosphere. Expect periods of
enhanced showers, mainly over windward areas, as pockets of moisture
move along with the trades. Dew points will likely creep up into the
lower 70s, raising humidity and giving the air a warmer feel even
with the trades blowing.

By the weekend, forecast models show a return to a more typical
trade wind pattern with mainly brief windward showers as moisture
gradually diminsihes. High pressure NNE of the islands will also
strengthen, driving increased trade winds.


A high pressure ridge locked in place north of the Hawaiian Islands
will keep moderate to breezy trades in the forecast for the next
several days. Wind speeds will be strong enough for low level
turbulence over and south through west of all island mountain
ranges. Expect brief passing showers and periods of low cloud
ceilings over windward and mountain areas. Mostly VFR conditions
will prevail with isolated MVFR.

AIRMET TANGO for turbulence remains in effect below 8,000 feet over
and immediately south through west of higher terrain. These
conditions will likely continue for the next few days.


Ridging will remain far north of the islands through the weekend and
continue to support locally fresh to strong trade winds.
Therefore, a Small Craft Advisory remains in effect for the waters
around Maui County and the Big Island through at least Wednesday

Small, long-period southerly swells will arrive through the week
with surf heights remaining below advisory levels. A short-period
southeast swell will linger through the week, keeping surf slightly
elevated along exposed shorelines. Easterly trades will continue to
produce elevated surf along east facing shores. A very small
northwesterly swell may arrive late in the week.


Small Craft Advisory until 6 PM HST Wednesday 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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