Heavy Rain in Hawaii, August 3, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
352 PM HST WED AUG 3 2016

.SYNOPSIS...
Moderate to locally breezy trade winds are expected to continue
through Friday as high pressure remains to the north of the
islands. Expected increasing showers tonight and tomorrow as an
area of enhanced moisture is carried in on the trades. The trades
will carry some of the showers to leeward areas at times. A
slightly drier period is expected Friday, with rain chances
increasing again during the weekend, when the remnants of former
tropical cyclone Howard are forecast to approach the islands from
the east.

&&

.DISCUSSION...
No significant changes to the forecast this afternoon. We are
already seeing some increases in shower activity, particularly
over the Big Island, with the area of increased low level
moisture moving in over the state from the east. High pressure
remaining north of the state will continue to bring moderate to
locally breezy trades to the region, so expect some of the showers
to reach leeward areas. This batch of low level moisture is
expected to clear out by Friday, given the area a day or so of
drier weather.

Heading into the weekend, the forecast reflects an increase in
rain, and winds shifting, in response to the remnants of former
tropical cyclone Howard reaching the islands. Howard was
downgraded to a post-tropical cyclone with the 11 am package from
the National Hurricane Center, which was then the last final
advisory. The models are in good agreement with the remnants
reaching the islands as a trough, bringing rain to the islands.
The details of how much rain and when are still being evaluated.
At this time the forecast reflects an increase in rain chances
Saturday afternoon through Sunday night and into Monday.

&&

.AVIATION...
An increasingly moist trade wind flow will continue to spread over
the island chain from the east tonight. The afternoon Hilo
sounding revealed that the inversion has been weakened
considerably, and day time convection over the leeward Big Island
slopes has been reaching over 15000 ft. Although the afternoon
Lihue sounding continued to show an inversion near 5000 ft, expect
the increasingly moist trade wind flow, now over the eastern half
of the state, to spread over all islands tonight. Periods of MVFR
ceilings and VIS can be expected over windward portions of all
islands tonight, and we will have to monitor for mountain
obscuration. Aside from some afternoon and evening clouds and SHRA
on leeward Big Island slopes, VFR will prevail for leeward areas,
though isolated passing SHRA are expected.

Airmet Tango is in place for low level turbulence. Conditions are
border line, and with the inversion expected to erode overnight,
the Airmet may be allowed to expire.

&&

.MARINE...
The Small Craft Advisory /SCA/ remains in effect for the typically
windier areas around the Big Island and Maui County. Locally
strong trade winds are expected into Friday. Over the weekend,
winds will become increasingly variable as the remnants of Post-
Tropical Cyclone Howard pass near or over the state.

Small background south swells will keep below advisory surf along
the south facing shores for the foreseeable future. The elevated
trade winds will keep seas choppy along the east facing shores
into Friday. Increasing east swells, from Tropical Storm Howard
and the distant Ivette, are expected to begin affecting the east
facing shores Friday and continue into next week. Advisory
conditions associated with Howard's swells are possible over the
weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Friday for Kaiwi Channel-
Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island
Leeward Waters-Big Island Southeast Waters.

&&

DISCUSSION...M Ballard
AVIATION...Wroe
MARINE...Eaton