Drought in Hawaii, July 1 to 31, 2019

Area Forecast Discussion
National Weather Service Honolulu HI
835 PM HST Sun Jun 30 2019

.SYNOPSIS...
A trade wind weather pattern is expected over the next couple of
days due to high pressure far northeast of the state. Clouds and
passing showers will tend to favor windward and mauka areas. Winds
will become lighter Wednesday through Friday as a trough of low
pressure approaches from the northwest. This will favor windward
showers during the overnight and morning hours, and interior and
mauka showers during afternoons and evenings. More typical trad
wind weather is expected to return next weekend as high pressure
strengthens northeast of the state.

&&

.DISCUSSION...
Currently at the surface, a persistent trough of low pressure is
located around 450 miles to the west of Kauai. Meanwhile, a pair
of high pressure systems are located far northeast and far north-
northwest of the island chain. The low level boundary layer flow
remains out of the east-southeast this evening, and this is
keeping the stronger winds northeast of the state, while light to
moderate trades prevail across the island chain. Infrared
satellite imagery shows mostly cloudy skies in place across the
vast majority of the state, with radar imagery showing scattered
showers in both windward and leeward areas. Main short term
concerns revolve around rain chances and trade wind trends.

High pressure far northeast of the state will remain nearly
stationary over the next 7 days. A weak disturbance within the
Intertropical Convergence Zone (ITCZ) around 750 miles south of
the Big Island, will pass by to the south of the islands over the
next couple days. This is expected to give a bit of a boost to
trade wind speeds, elevating them to moderate levels through
Tuesday. The western edge of the surface ridge will weaken during
the middle of the week as a surface trough of low pressure
approaches from the northwest. This is expected to the lighten the
trade winds enough to allow for daytime sea breezes and overnight
land breezes Wednesday through Friday, particularly across the
western islands. The surface ridge is then expected to strengthen
next weekend, bringing a return of moderate to locally breezy
trade winds.

The convergent east-southeasterly boundary layer flow will keep
scattered showers in place through the remainder of the evening.
Shower coverage is expected to diminish after midnight in leeward
areas, although isolated showers will remain possible. Scattered
showers will continue in windward locales through the night. We
expect a fairly typical trade wind pattern featuring scattered
windward showers and isolated leeward showers through the first
couple days of the new week, with coverage the highest during the
night and early morning hours. There could be some leeward shower
development each afternoon as well given the east-southeasterly
boundary layer flow and lingering humid airmass. During the middle
to latter part of the work week, showers will favor windward and
mauka areas during the overnight and morning hours, and interior
and mauka areas during the afternoon and evening. A more typical
trade wind pattern will return next weekend, featuring scattered
windward showers and the occasional leeward spillover.

&&

.AVIATION...
East-southeast flow, combined with moist conditions in the lower
levels, will allow for scattered shower development across the
region tonight. Most activity will be concentrated along the
windward coasts and slopes, although isolated activity could push
over the leeward sides. MVFR conditions are likely above 2000 ft
due to mountain obscuration from the low clouds and precipitation.

AIRMET Sierra remain in effect above 2000 feet on north thru east
sides of all islands due to mountain obscuration from clouds and
SHRA.

&&

.MARINE...
Surface high pressure located far northeast of the state will
maintain trade winds across most of the coastal waters into
Tuesday. A weak disturbance moving by well south of the state on
Monday might provide a slight boost in trade wind speeds. The
trades are expected to weaken, and possibly shift out of the
east-southeast, from Tuesday night into this weekend. Therefore,
no Small Craft Advisory conditions are in the forecast through
Friday, including the Fourth of July Holiday. Easterly trade
winds may start to return across the area late next weekend.

The nearshore buoys continue to show energy from the current
long-period south-southwest swell. Surf produced by this swell
appears to be near its expected peak, so surf will gradually
lower from early Monday morning through Tuesday. A High Surf
Advisory (HSA) remains in effect for south facing shores of all
Hawaiian Islands through Monday afternoon. Additional swells
arriving from the South Pacific are expected to keep surf heights
above the summer-time average, but below the HSA criteria, along
south facing shores from Tuesday through Friday.

Elsewhere, the current small trade wind swell will likely
maintain modest surf along east facing shores into Tuesday. Surf
will gradually lower from late Tuesday through Friday as the
trades weaken.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Monday for Niihau-Kauai
Windward-Kauai Leeward-Oahu South Shore-Waianae Coast-Molokai
Leeward-Lanai Makai-Kahoolawe-Maui Leeward West-Maui Central
Valley-Windward Haleakala-Leeward Haleakala-Kona-South Big
Island-Big Island North and East.

&&

DISCUSSION...Jelsema
AVIATION...Thomas
MARINE...Houston