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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 040156
Area Forecast Discussion
National Weather Service Honolulu HI
356 PM HST Mon Aug 3 2020
Moderate to breezy trade winds will continue through the week.
Through much of the week, a typical trade wind weather pattern
will focus clouds and showers over windward slopes along with
afternoon showers over leeward Big Island. A passing disturbance
aloft may cause an uptick in showers from Wednesday through
Friday. A decrease in showers and an increase in winds is
expected by the weekend.
Moderate to breezy trade winds and a fairly typical weather
pattern remains in place. The trades are being driven by broad
surface high pressure far north of the state. A mid-level ridge
overhead is maintaining stable conditions with an inversion based
between 5,000 to 7,000 ft, and precipitable water is running
below August normal, which lead to scant rainfall over most
islands today after a somewhat active night of showers. In
addition, a narrow upper-level trough is sending thin high clouds
over Kauai and Oahu.
Only subtle changes are expected through tomorrow. Trades will
hold around current strength. Typical windward rainfall is
expected for the western half of the state. A narrow slot of
drier air will favor suppressed shower activity on the Big Island
and Maui overnight, followed by an increase in showers on the Big
Island as a band of moisture largely skirts by to the south on
An increase in shower activity is possible Wednesday through
Friday. A mid-level trough will slowly move over the state from
east to west, increasing precipitable water and destabilizing the
lower atmosphere. Expect periods of enhanced showers, mainly over
windward areas, as pockets of moisture move along 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. High
pressure north of the islands will also strengthen, driving
increased trade winds.
High pressure anchored far north of the state will maintain
moderate to locally breezy trade wind flow across the main
Hawaiian Islands. The air mass over the state will remain mostly
dry and mostly stable. An inversion aloft around 7ktf will limit
Clouds and isolated showers will favor island interiors in the
afternoon and evening hours, then mainly north and east facing
slopes and coasts during the late night and morning hours.
Localized MVFR CIG and VIS are to be expected in showers, but VFR
conditions will predominate throughout the period.
AIRMET TANGO for turbulence remains in effect below 8,000 feet
over and immediately south through west of higher terrain.
Ridging will remain far north of the islands through the weekend
and continue to support locally fresh to strong trade winds. A
Small Craft Advisory remains in effect due to channeling near the Maui
County and southern Big Island waters through at least Wednesday
There will be small long period southerly swells arriving 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 shorter period choppy surf along
east facing shores. Very small northwesterly swell may exist 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