High Surf in Hawaii, June 21 to 23, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
412 AM HST TUE JUN 21 2016

.SYNOPSIS...
High pressure north of the state will keep a moderate trade wind
flow in place through early next week. Clouds and showers will
focus primarily over windward and mauka areas, but an occasional
shower will drift into leeward areas mainly during the overnight
and early morning hours.

&&

.DISCUSSION...
Currently at the surface, a strong 1038 mb high is centered around
1500 miles north of Honolulu, driving the moderate trade winds
across the island chain. Upstream, a weak trough of low pressure
is located around 800 miles northeast of Hilo. Infrared satellite
imagery shows partly to mostly cloudy skies in place across the
state. Meanwhile, radar imagery shows showers affecting mainly
windward and mauka areas, with a few drifting into leeward areas
as well. Main short term concern for today revolves around rain
chances.

Today,
High pressure will remain centered well north of the state,
keeping a moderate trade wind flow in place. Satellite and radar
imagery show an area of enhanced clouds and showers affecting Maui
county and Oahu, while remaining just upstream of Kauai, with
MIMIC total precipitable water values running between 1.5 and 1.7
inches. Precipitable water values upstream of Maui county and the
Big Island are generally in the 1.2 to 1.5 inch range, fairly
close to climatological norms. The area of enhanced clouds and
showers will focus mainly across Oahu and Kauai this morning as it
shifts eastward within the trade wind flow, with some disruption
expected for the afternoon as a result of daytime heating. A wet
trade wind pattern is therefore expected across Kauai and Oahu
this morning, with a more typical trade wind set up for Maui
county and the Big Island.

Tonight through next Monday,
A persistent trade wind weather pattern will remain in place as
strong high pressure remains centered well to the north of the
island chain. There will be some minor fluctuations in the trade
wind speeds, but overall moderate trades are expected to prevail,
with slightly enhanced speeds for Thursday and Friday as the
surface trough northeast of the state dissipates. Bands of
enhanced moisture will move through the area within the trade wind
flow, with clouds and showers focusing primarily over windward and
mauka locales. Showers will periodically affect leeward areas of
the smaller islands as well, mainly during the overnight and early
morning hours.

&&

.AVIATION...
Under moderate to locally breezy trade winds, AIRMET Tango
remains posted for low level turbulence leeward of the higher
terrain on all islands. This AIRMET will likely remain in effect
through today, since little significant change is expected in
the background trade wind flow.

A diffuse area of low level moisture moving along the low level
trade wind flow has been focused mainly over the windward
sections of some of the islands overnight. As a result, brief
periods of MVFR CIGS / VIS due to low clouds and SHRA will likely
continue this morning over most windward facing slopes and some
of the higher terrain. Otherwise, expect VFR conditions to prevail
over leeward areas of all islands today.

&&

.MARINE...
Fresh to locally strong trade winds associated with high pressure
centered north of the state will continue through the week and
into the upcoming weekend. The roughest conditions will remain
across the typical windier marine zones between Molokai and the
Big Island. The latest nearshore wave guidance reflects this and
depicts the highest seas ranging from 7 to 10 ft over the waters
south of the Big Island and across the Alenuihaha Channel each
day. As a result, the small craft advisory will remain up for
these areas and will likely be extended in later packages.

In addition to the local winds and seas, the current long-period
south swell has slightly increased through the overnight hours based
on the latest Barbers Point and Lanai PACIOOS buoy observations.
This southerly source will hold through the mid-week period, then
begin to ease by Friday. Surf associated with this swell should
remain just below advisory level through this time along south
facing shores...however...it will need to be monitored. A small
southerly swell will be possible again Sunday through early next
week.

Surf along east facing shores will remain rough through the
remainder of the week as a result of fresh to locally strong
trade winds associated with high pressure north of the region. A
slight increase in the surf along east and north facing beaches
will be possible Wednesday night through Friday as a small north-
northeast swell fills in. Breakers should remain below the
advisory level along east facing shores through this time.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

&&

Discussion...Jelsema
Aviation...Houston
Marine...Gibbs