Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Honolulu HI
1146 am HST Sat Aug 1 2015
minor changes to the wind forecast on Wednesday and Thursday for
Hurricane Guillermo/S adjusted track and intensity.
moderate to fresh trades will continue through Monday...then
weaken by Tuesday as Hurricane Guillermo disrupts the flow. Showers
will increase as remnant moisture associated with former tropical
depression 08e reach the islands today and on Sunday...with best
chances of rain over windward and southeastern portions of The Big
Island. The forecast for next week will be highly dependent on the
eventual track of Hurricane Guillermo...but anticipating a wet weather
pattern across the islands Tuesday night through Thursday night.
Previous discussion.../issued 959 am HST Sat Aug 1 2015/
A broad high pressure is centered far north of the state driving moderate
to fresh trades across the islands through Monday. Visible
satellite and radar show scattered clouds and showers impacting the
windward sides of the islands this morning with mostly sunny skies
across the leeward areas. Temperatures will continue to be warm
with highs in the upper 80s to low 90s and lows in the middle
70s...but the breezes will make conditions a little more bearable.
The Big Island will be impacted by clouds and rainfall associated
with the remains of tropical depression 08e today through Sunday
night or Monday. Thunderstorms have recently reformed near the
center of 08e...but these will likely pass south of The Big
Island as the moisture expected to impact will be on the northern
periphery of the Post-tropical cyclone. Windward and southeast
portions of The Big Island will be most impacted by the
rain...and could become locally heavy at times. Trade winds will
carry some of the moisture from 08e over the windward smaller
islands tonight and Sunday...but showers will not be as
concentrated as on The Big Island.
Models show winds weakening across Hawaii Monday night into
Tuesday as Hurricane Guillermo begins to disrupt the trade wind
flow. We will begin to feel the effects of Guillermo by Tuesday
night with an increase in cloud cover and rainfall. These effects
will continue through Thursday night as Guillermo reaches or
passes near the islands. However...it is important to keep in mind
that the overall forecast scenario will continue to evolve during
the next several days as new track and intensity forecasts are
Long range models show moderate to locally fresh trade winds
building back over the state this weekend.
VFR conditions prevail at most taf sites with the exceptions of phto
phny and phli where there has been occasional MVFR conditions being
reported due to low clouds and rain showers. Expect these conditions to
continue through the day especially at phto as moisture associated
with former tropical depression 08e moves into The Big Island from
the east. Airmet Sierra remains posted over the windward Big Island
slopes due to low clouds and rain showers.
Airmet Tango remains posted over and immediately south and west of
mountain ranges of all islands due to moderate to fresh trade winds.
a Small Craft Advisory /sca/ is in effect over the typically
windier areas around Maui and The Big Island through 6 am HST
Sunday. The Small Craft Advisory is in effect for breezy trade winds accelerating
through the island terrain. The driving high pressure system is
expected to weaken and slide northeast away from the state Sunday
or Monday which will allow winds to weaken.
Hurricane Guillermo...located far east-southeast of The Big
Island...will continue to move toward the west northwest and reach
the central Pacific waters later today. Although the track and
intensity of the tropical cyclone remains uncertain so far in the
future...adverse effects for Hawaiian coastal waters next week can
not be ruled out.
That being said...swell generated from Guillermo is aimed towards
Hawaii from the east-southeast. Anticipating forerunners from this
swell to reach the eastern part of the state as early as Sunday
afternoon. The swell will build surf heights to advisory
heights along the east facing shores by Sunday night which will
likely linger through much of the week as Guillermo reaches or
passes by Hawaii. A high surf advisory will likely go into effect
Sunday afternoon or night for east facing shores.
Small Craft Advisory until 6 am HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island leeward waters-Big
Island southeast waters.