High Surf in Hawaii, July 2 to 5, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
329 AM HST SAT JUL 2 2016

.SYNOPSIS...
Strong and gusty trade winds will affect the state through
today, with a slight drop in winds expected for the rest of the
holiday weekend. A dry and stable air mass will result in rather
dry conditions with very little rainfall through today. The
airmass will gradually moisten from the east tonight through the
remainder of the holiday weekend, leading to increased showers
that will periodically spread leeward on the smaller islands. A
fairly wet moderate to breezy trade wind pattern will prevail
during the early to middle part of next week, followed by lighter
trade winds and somewhat drier conditions for the later part of
the week.

&&

.DISCUSSION...
Mainly dry and windy conditions prevail across the Aloha State on
this early Saturday morning. Rain gauge and radar data show some
light rainfall amounts over windward sections of Maui and the
Big Island. The strong trade winds are being driven by surface
high pressure centered about 1200 miles NNE of Oahu. Aloft, an
upper level low is centered several hundred miles west of Kauai,
and continues to bring areas of high-level cloudiness over the
islands. A mid level ridge is located just to the northeast of the
islands, and a very stable airmass is present over the state. The
12Z Lihue sounding shows a low/strong inversion based around 5k
feet, with strong low-level winds ranging from 25 to 35 kt.

A few locations around the state have observed wind advisory
criteria conditions of 30 mph sustained winds or 50 mph wind
gusts thus far during this event. Most areas have seen sustained
winds of 20-25 mph and peak gusts in the 40-45 mph range. The
latest model guidance continues to indicate that the strongest
winds are occurring now and will continue into this morning before
slowly diminishing. Model soundings show low-level winds near 30
kt during this time, with the inversion remaining strong and lower
than usual. This combination of factors will continue to produce
conditions conducive for strong wind gusts over and downwind of
island terrain. A wind advisory remains in place through 6 PM
today for the entire state, and there is a small chance that the
Haleakala summit will see high wind warning conditions. Otherwise,
rather dry conditions will persist today. The above mentioned mid
level ridge and unusually low inversion will keep low-level
moisture minimal. A few showers may affect the windward Big
Island and windward East Maui, but little to no rain is expected
elsewhere.

Trade winds will ease somewhat tonight and Sunday, and shower
activity is expected to return to more normal levels as the
inversion rises and increased low-level moisture moves into the
state from the east. Expect passing but more frequent showers over
windward areas, with the breezy trade winds carrying some showers
over leeward portions of the smaller islands at times.

A somewhat wet moderate to breezy trade wind pattern appears to
be in store from Sunday night through at least Tuesday, as areas
of increased low-level moisture move through the state, while
forecast soundings show the inversion up between 8 and 10 thousand
feet. Showers will remain most frequent over windward areas, but
should be numerous and substantial enough so that some will be
carried leeward in the trade wind flow. Somewhat drier and less
breezy trade wind conditions may develop around midweek and
continue through the later part of the week.

The high clouds that have been producing periods of interesting
sky conditions during the past several days will thin over at
least the eastern half of the state today as the upper level low
to our west drifts further away and ridging noses in from the
southeast. Thicker high clouds will likely return by Tuesday and
continue through midweek as the upper trough to our west
strengthens once again.

&&

.AVIATION...
Strong, gusty trade winds and stable atmospheric conditions will
persist, supporting the continuation of AIRMET Tango for moderate
to isolated severe low level turbulence over and immediately S
through W of terrain on all islands. Sustained surface wind speeds
of 30 knots is also included in AIRMET Tango.

VFR conditions will prevail, with the stable trade wind flow
providing shallow low clouds that may occasionally become
widespread enough along windward slopes and coasts to lead to
isolated MVFR ceilings.

&&

.MARINE...
Recent observations from the nearshore PACIOOS buoys have been
running around 1 to 2 ft lower than predicted this morning, which
indicates the current wind forecast over the waters could be running
slightly too high. The overnight ASCAT pass, however, did clip the
Kauai waters and showed wind magnitudes ranging from 20 to 25 knots.
This combined with the potential of the local winds slightly
increasing further will support keeping the current advisory and
gale warning in place through the day today. Although the winds will
begin to ease Sunday through the upcoming week, the Small Craft
Advisory will likely be extended in later forecast packages, mostly
for the windier marine areas from the Pailolo Channel to the waters
south of the Big Island.

Advisory-level surf will remain possible along the east facing
beaches due to the strong trade winds, beginning as early as
tonight. Elsewhere, no significant surf is anticipated through the
weekend. Looking ahead through the upcoming week, the latest hi-res
wave model guidance has begun to reflect a small to moderate south
swell by the end of next week in response to the recent gale located
east of New Zealand. Although later observations at the buoys
farther south across the Pacific will need to be monitored over the
coming days, this southerly source will likely support near advisory-
level surf along the south facing shores by next Friday. Please
refer to the recently issued Collaborative Nearshore Swell and Wind
Forecast (SRDHFO) for more details.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM HST this evening for all Hawaii islands.

Gale Warning until 6 PM HST this evening for Pailolo Channel-
Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters.

Small Craft Advisory until 6 PM HST this evening for Kauai
Windward Waters-Maui County Leeward Waters-Big Island Windward
Waters.

Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest
Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters-
Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-
Maalaea Bay.

&&

DISCUSSION...Jacobson
AVIATION...Birchard
MARINE...Gibbs