Heavy Rain in Hawaii, June 2 to 5, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
335 PM HST THU JUN 2 2016

.SYNOPSIS...
Trade winds will weaken over the next 24 hours as the ridge north
of the islands is eroded and a surface trough moves to within
several hundred miles northeast of the state. Daytime sea breezes
and nighttime land breezes will become more widespread from Friday
night through the weekend. Sea breezes will produce afternoon
interior clouds and showers, some briefly heavy this weekend, and
land breezes will bring partial clearing at night. Trade winds
will return next week as high pressure builds north of the state.

&&

.DISCUSSION...
Moderate trade winds will steadily decline tonight. The surface
ridge driving the trades sits north of the state along 29N and is
being eroded by a deep trough and its associated front dropping
down from the north. As this process continues, a weak surface
trough, now located about 575 miles northeast of the state, will
drift closer. The result will be a steady decrease in the trades
tonight and Friday.

A typical rainfall pattern will focus modest showers along
windward slopes tonight, as the band of deep moisture that
affected the state during the past few days has cleared to the
south. Mid level ridging will maintain stable conditions with an
inversion in the 7000 to 9000 foot range. Aside from evening
clouds and isolated showers on the Big Island, leeward areas will
be rather dry.

Lighter winds are due for most islands for Friday and the weekend.
By the afternoon, the surface trough will stall roughly 350 miles
northeast of the islands, while the ridge to the north continues
to erode. This will weaken and eventually cut off trade winds over
the Big Island as well as most of Maui County heading into the
weekend, while northeast winds hold over Kauai and, to a lesser
degree, on Oahu. With the exception of Kauai where windward
showers will prevail, a land and sea breeze regime will dominate,
featuring afternoon clouds and spotty interior showers followed
by a clearing trend at night. The GFS and ECMWF are showing
moisture associated with the band currently south of the state
being drawn back up over the Big Island during the weekend,
suggesting showers will be more active there. In addition,
conditions could become slightly unstable on Saturday as a mid to
upper level trough swings by, placing the highest chances for some
isolated heavy afternoon showers on that day.

Trade winds will rebuild late Sunday and Monday as the surface
trough to the northeast moves away and surface high pressure
strengthens far north of the islands.

&&

.AVIATION...
Moderate trade winds will ease tonight as a weak surface trough,
several hundred miles northeast of the Big Island, moves north of
the state. Western portions of the state should expect light north
winds by Friday morning, while eastern portions will see light and
variable winds leading to a land-sea breeze pattern.

Overnight clouds and showers will continue to focus along windward
and mountain areas. Overall, conditions should stay predominately
VFR with select passing showers carrying MVFR CIGS/VIS.

A subtropical jet moving over the state may introduce light to
moderate upper level turbulence between FL300 and FL400. As of
0200Z, the only upper level turbulence report has been 225 NM
west of Kauai. This area corresponds nicely with the turbulence
guidance, keeping the highest chances west of the state into the
night. Therefore, no AIRMET Tango has been issued over the state.
Guidance shows a more increased chance for turbulence closer to
the state starting early Friday morning as a polar jet pushes
south.

&&

.MARINE...
No marine advisories are expected through at least the weekend.
Moderate trade winds will decrease over the next 24 hours then
become light and variable over the eastern end of the state for
the weekend. Trades will rebuild early next week, with small craft
advisory level winds possible over the typical areas around Maui
and the Big Island by midweek.

Small swells are due through most of the upcoming week. Energy
from the current mix of south-southeast and southwest swell has
dropped slightly today and will fade during the weekend. A larger
south-southwest swell is possible during the middle of next week.
A small northwest swell is also possible this weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

Public and Marine...Wroe
Aviation...Eaton