High Surf in Hawaii, June 4 to 6, 2018

Area Forecast Discussion
National Weather Service Honolulu HI
337 AM HST Mon Jun 4 2018

.SYNOPSIS...
Trade wind weather will continue through the forecast period as a
surface high to our north shifts southwest through Wednesday,
then moves east afterwards through next weekend. Trade showers may
become more active after midweek as an upper low moves southwest
over the area.

&&

.DISCUSSION...
There is no change in forecast philosophy from last evening. A
1032 mb high about 930 miles north of the main Hawaiian Islands,
near 34N158W, continues to drive locally breezy trade winds
across the area this morning. Radar shows isolated to scattered
showers moving across windward shores of the islands. Water vapor
loop shows an upper trough extending from a low aloft far
northeast of the islands to another low far west of Kauai.

Models show the high to the north of the islands will move south
through Wednesday. The pressure gradient south of the high will be
steep enough to produce locally breezy trade winds through
Tuesday. The trade winds will carry showery low clouds over the
islands through the week. The atmosphere is expected to remain
rather stable for the next couple of days, so rainfall amounts
will remain light with showers focused over mainly windward areas.
Leeward areas will be mostly dry except for afternoon showers
over the lee slopes of the Big Island.

The low aloft northeast of the islands will move slowly south
through Tuesday, linger over the islands through Thursday morning,
then move off to the northeast. High clouds will increase as the
upper low approaches. These clouds will not produce any rainfall,
but skies will be mostly cloudy to overcast at times. By mid-
week, the low aloft will help weaken the trades, and wind speeds
will become moderate. The atmosphere will become more moist and
unstable starting Thursday, so showers are expected to become more
active.

A Special Weather Statement (SPS) was reissued this morning for
ashfall around Kilauea summit following an earthquake late
yesterday afternoon. We will likely continue this SPS through
today.

&&

.AVIATION...
Expect predominately VFR conditions, with periods of MVFR CIG/VIS
mainly over windward slopes with passing showers in a typical
trade wind pattern. AIRMET Sierra for Tempo Mountain Obscuration
was issued this morning for windward slopes with low ceilings
expected to diminish for most areas by late morning.

Breezy to locally windy trade winds will continue today. AIRMET
Tango for Tempo Moderate low level turbulence over the mountains
and south through west sections remains in effect for all islands.

Volcanic Ash SIGMET Uniform remains in effect for volcanic ash
emissions near the Kilauea/Halemaumau crater. Winds will continue
to carry any ash towards the southwest and west. Volcanic
emissions will continue to produce areas of MVFR VIS are over
southern sections of the Big Island.

&&

.MARINE...
Surface high pressure far north of the state will maintain
locally strong trade winds into mid-week. As a result, a Small
Craft Advisory (SCA) is in effect through Tuesday afternoon for
the Kaiwi Channel, all waters surrounding the islands of Maui
County, and the typically windy waters adjacent to the Big Island.
Trade wind speeds are expected to decrease slightly by late
Tuesday, but the latest forecast maintains SCA conditions Tuesday
night and Wednesday across the typically windy waters adjacent to
the Big Island and islands of Maui County.

Buoys near south Oahu continue to show the current long-period
south swell appears to be gradually increasing early this
morning. The most recent observations from the newly deployed
PacIOOS Barber's Point buoy (51212) show a significant wave
height of about 4 feet with a wave period of near 17 seconds.
Note that this new buoy appears to have minimal contamination from
the trade wind swell. A High Surf Advisory (HSA) has been issued
for south facing shores of all Hawaiian Islands through early
Tuesday morning. This south swell is forecast to gradually subside
from Tuesday through Thursday. Another long-period south swell is
forecast to arrive by early Friday. Surf produced by this swell
may reach the HSA criteria along south facing shores next weekend.

Elsewhere, the locally strong trade winds will maintain rough
surf along the east facing shores this week. A couple of small
northwest swells may produce a slight bump in surf along some
north facing shores of the smaller islands from Wednesday into
this weekend.

&&

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

Small Craft Advisory until 6 PM HST Tuesday for Kaiwi Channel-
Maui County Windward Waters-Maui County Leeward Waters-Maalaea
Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-
Big Island Southeast Waters.

&&

DISCUSSION...Powell
AVIATION...Bohlin
MARINE...Houston