|Wind||NE 26 mph|
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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 041335
Area Forecast Discussion
National Weather Service Honolulu HI
335 AM HST Tue Aug 4 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
late tonight into Friday.
In summary, trade winds will prevail for the foreseeable future,
supported by persistent high pressure to the N and NE. The trades
will deliver 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 later tonight into
Friday, favoring windward areas, and most active during nights and
mornings. The trade-wind-supplying high 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 a
few high clouds that are not expected to be very thick.
Moderate to breezy trade winds and a fairly typical weather pattern
will remain in place through this evening, with a mid-level ridge
maintaining a subsidence inversion based around 7 kft, and PWAT
running below August norms at about 1.0". An increase in shower
coverage appears likely later tonight into Friday as an area of
higher PWAT (near 1.7"; currently crossing 150W) moves over the
islands. Dew points will likely creep up into the lower 70s, raising
humidity and giving the air a warmer feel, even with the trades
blowing. A mid-level trough will also move over the islands from the
E, destabilizing the lower atmosphere. The combination is expected
to lead to periods of enhanced showers, mainly over windward areas,
with the trades driving a few rain drops leeward on the smaller
islands. The Big Island's leeward slopes will see afternoon and
evening clouds developing in response to sea breeze convergence that
will drop a few showers.
By the weekend, a return to a more typical trade wind pattern is
expected, with mainly brief windward showers as moisture gradually
diminishes. 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