Wildfire in Hawaii, May 19 to 22, 2019

Area Forecast Discussion
National Weather Service Honolulu HI
954 AM HST Sun May 19 2019

.SYNOPSIS...
A trade wind weather pattern will prevail through tonight with
clouds and passing showers favoring windward and mauka areas. A
front will approach the area on Monday and remain northwest of
the area through Friday. Winds will be lighter with daytime sea
breezes and nighttime land breezes prevailing. Showers will tend
to favor interior and mauka areas but a few showers are also
possible over leeward areas at times. Trade winds may return by
next weekend.

&&

.DISCUSSION...
High pressure, both at the surface and aloft, is presently
centered far northeast of the state. This places the islands in a
moderate trade wind environment. An area of moisture riding along
in the easterly trade wind flow, is providing for some passing
light showers over windward and mauka sections of Kauai and Oahu
with generally dry conditions prevailing elsewhere. A few thin
high cirrus cloud will also be moving over the area today from the
southwest but will likely not dim the sunshine all that much.

The large scale weather pattern will begin to change on Monday as
a cold front approaches the state from the northwest. This will
cause the high pressure ridge to be displaced to the southeast,
with the low level wind flow becoming lighter and from an east
southeastly direction. This lighter wind pattern will allow for
daytime sea breezes and nighttime land breezes to develop across
many ares. Shower activity during the afternoons and evenings will
tend to develop over interior areas due to daytime heating and sea
breeze convergence, but could occasionally drift over some leeward
locations. During the nighttime hours, showers will be focused across
areas of low level convergence primarily over windward and mauka
areas. This weather pattern will continue on into at least Friday
as the front remains stalled northwest of the state.

As we head into next weekend, subtle model differences show up in
the global models. The GFS shows moderate trade wind returning
while the ECMWF shows only light trades possibly returning. The
current forecast currently favors the GFS since this blends in
well with late May climatology. Showers would then then to favor
windward and mauka areas.

&&

.AVIATION...
High pressure to the northeast of the islands will help to
maintain moderate easterly or east southeasterly flow today.
ISOL -SHRA will occur along the windward slopes and coastal area
with dry and VFR conditions elsewhere. Expect more of the same
tonight with highest concentration of low clouds and -SHRA along
the windward coasts and slopes.

AIRMET SIERRA remain in effect above 2000 feet for the northeast
facing slopes on Oahu for tempo mountain obscuration.

&&

.MARINE...
High pressure northeast of the state will keep moderate to
locally strong trade winds in place through tonight. As a result,
a Small Craft Advisory (SCA) remains in effect for the typically
windy waters around Maui and the Big Island through 6 AM Monday.
The winds will ease and shift around to the east-southeast Monday
through Tuesday, as the high moves northeast and a cold front
approaches from the northwest. The front will then stall northwest
of the area during the middle and latter part of the week, while
high pressure strengthens northeast of the island chain. This will
bring a slight increase in the east to east-southeasterly winds
Wednesday through Friday.

A series of small southwest and south swells will produce small
to moderate surf along south facing shores through the middle of
the week. A larger long-period south-southwest swell is expected
to arrive during the Memorial Day weekend, with surf possibly
reaching advisory levels along south facing shores.

The current small northwest swell peaked overnight last night and
will be on a decline through Monday. North shore surf will remain
small Monday night through Thursday, with a new small to moderate
sized northwest swell possible Friday into the Memorial Day
weekend. Surf along east facing shores will remain small through
the middle of the week. A developing fetch of moderate trades
upstream of the islands could bring a boost to east shores surf
Thursday through the Memorial Day weekend.

&&

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

&&

DISCUSSION...Burke
AVIATION...Thomas
MARINE...Kino