Drought in Hawaii, April 1 to 30, 2019

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Sun Mar 31 2019

.SYNOPSIS...
A front approaching the state will reach Kauai Monday, then stall
and dissipate over the central islands. Showers will increase ahead
and along the front. Trade winds will return to the islands Tuesday
as high pressure builds behind the front. Light showers will favor
windward and mauka areas Tuesday through Friday. Winds will become
light toward the weekend as the high moves to the northeast of the
area.

&&

.DISCUSSION...
Showers have increased a bit across some of the islands this evening
as a front approaches the area from the northwest. Much of the
showers activities are over the Big Island, with Oahu saw some
heavier showers earlier this evening. Airmass has also become
unstable enough for some thunderstorms to develop over northeast Big
Island coastal waters. As the moisture will linger in the island
vicinity, specially over the southern islands, while airmass will
stay somewhat unstable, do expect a little more showers to affect
mainly the southern islands with isolated thunderstorms through rest
of the evening into early Monday morning. The upper level trough
associated with the front has also brought rather strong winds over
the Big Island summits earlier Sunday. Thus a Wind Advisory remains
in effect for those areas.

The front is forecast to reach Kauai by about midday Monday and then
dissipate over the central islands late Monday into Tuesday. Winds
will turn northerly and increase behind the front. This front will
be rather shallow, with the greatest chances for showers expected
over north facing slopes of Kauai and Oahu.

High pressure will build northwest of the islands behind the front,
with moderate northeast trade winds returning over the area. Some
light showers will likely to focus along windward and mauka areas
under this weather regime. The high will move from west to east with
winds turning more easterly by Wednesday through Thursday night.

The high will move off to the northeast of the area Friday and
Saturday as another front gradually approaches the area from the
northwest. Winds will become light once again as the front moves
closer to the area. This will allow more widespread daytime sea
breezes and nighttime land breezes to develop over the islands. No
significant increase in showers is expected for now as the airmass
is forecast to stay somewhat stable. But then forecast model
solutions do diverge a bit upon how far south this next front will
advance to.

&&

.AVIATION...
Instability is on the increase across the island chain as a front
approaches from the northwest and a weak surface trough remains
nearly stationary northeast and east of the Big Island. Spotty
showers, and a chance of a thunderstorm over Big Island windward
waters, are possible through the nighttime hours. Predominantly,
winds will be light and variable through Monday morning. VFR will
hold sway, however.

No AIRMETS are currently in effect.

&&

.MARINE...
The gradient between a ridge of high pressure near the Big Island
and an approaching front is supporting light to locally moderate SW
to W winds over the marine area this evening. Showers are primarily
scattered in coverage and moving toward the NE, except for numerous
showers over windward Big Island waters. A particularly active
thunderstorm erupted over windward Big Island waters (about 20-40 nm
NE of the Hamakua coast) around sunset, and continues to linger,
apparently associated with a weak surface trough.

The front will move into Kauai coastal waters Monday morning, then
gradually move SE toward Oahu while weakening Monday night while the
aforementioned trough dissipates. High pressure building N of the
area will support a switch to moderate to locally fresh N to NE
winds as the front passes, with the front eventually dissipating
over the central portion of the island chain by Tuesday. This high
will move very slowly toward the E through the week, supporting
moderate to fresh trade winds that will eventually veer from NE to E
from Tuesday through Thursday. Light and variable winds are expected
Friday as the ridge moves over the islands once again, in advance of
another approaching front. Thereafter, the process described above
is expected to repeat, with the front dissipating near (or N of) the
islands, and high pressure building to the N bringing a return of
light to moderate N to NE winds next weekend.

A Small Craft Advisory (SCA) will likely be required for windier
areas around Maui and the Big Island as trade winds peak around
midweek. Additionally, seas may reach the SCA criteria of 10 feet in
waters around Kauai and Oahu Monday night/Tuesday as an
advisory-level long-period NW swell arrives. In the meantime, surf
will be below advisory levels as today's WNW swell diminishes and a
slight pulse from the NW arrives on Monday. Surf will gradually
diminish below advisory levels Wednesday into Thursday. Another NW
swell arriving Friday into the weekend may approach advisory levels,
but forecast guidance has been inconsistent in the depiction of the
source low's track. Otherwise, little significant surf is expected
elsewhere.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 AM HST Tuesday for Big Island Summits.

&&

91.22.97.84