High Surf in Hawaii, January 12 to 14, 2017

Area Forecast Discussion
National Weather Service Honolulu HI
345 PM HST Thu Jan 12 2017

.SYNOPSIS...
A powerful storm in the north Pacific created a swell that will
produce very large surf along north and west facing shores starting
early Friday morning. A surface ridge will remain over the islands
through Saturday. The ridge will bring mostly dry and hazy weather.
The ridge will shift north slowly early next week allowing trade
winds to gradually build over the islands.

&&

.DISCUSSION...
A ridge, at the surface and aloft, will remain near the islands
through Saturday. Moderate east southeast winds near the Big Island,
veer to south southeast over Kauai. The Big Island and Maui block
much of the low level flow so winds will be light and variable on
the smaller islands. The light low-level flow will allow nighttime
land breezes and daytime sea breezes to prevail. The sea breezes
will produce afternoon cloudiness over interior areas but the
atmosphere will remain stable so rainfall will be sparse. The east
southeast winds will carry volcanic emissions from Kilauea (VOG)
over the smaller islands, so it will remain hazy through the weekend.

The global models are in good agreement showing surface pressures
building northeast of the state early next week. The surface ridge
near the islands will strengthen and shift north and trade winds
will build over the islands. The trade winds will help clear the vog
early next week. Trade winds could become breezy by mid-week.
Returning trade winds will likely bring windward showers, but the
atmosphere is expected to remain rather stable, so no excessive rain
is likely.

&&

.AVIATION...
There are no AIRMETs in effect and none are expected through
tomorrow. A surface ridge near Kauai will remain nearly stationary.
Moderate to locally fresh east winds south of the Big Island will
veer to south southeast near Kauai. Daytime sea breezes and
nighttime land breezes will prevail. The ridge will maintain stable
conditions over the area. VFR will prevail at the TAF sites over the
main Hawaiian islands, but TEMPO MVFR is possible over interior
areas, including Lanai Airport, during the afternoons.

&&

.MARINE...
The current northwest swell continues to subside. Surf from this
swell has dropped below the high surf advisory level.

A hurricane force low in the north Pacific has produced a very large
west northwest swell headed toward the islands. Forerunners from
this swell had reached buoy 51001 by 200 PM and will reach Kauai
this evening.  Surf along exposed north and west facing shores will
build above the 25 ft High Surf Warning level Friday morning on the
smaller islands. Since this swell will be coming from a west
northwest direction, the surf will be partly blocked by Kauai and
Niihau, so surf will be smaller on Oahu than Kauai County. On the
other hand, this west northwest direction will allow quite a bit of
the swell energy to pass south of Kauai and Niihau and reach west-
facing shores of the Big Island. Surf is expected to reach the 12 ft
High Surf Warning level on the west-facing shores of the Big Island
by Friday evening.

Another very large swell is likely around the middle of next week,
but there is some uncertainty about the exact size and timing of
the swell.

The ridge near the islands will keep winds over the coastal waters
relatively light through the weekend, so no Small Craft Advisories
for winds are expected over the next few days. Combined seas will
rise above the 10 ft Small Craft Advisory threshold in areas of the
coastal waters exposed to the large swell. Locally strong trades may
return by the middle of next week as high pressure builds northeast
of the area.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning from 600 AM Friday for north and west facing
shores of Niihau Kauai Oahu and Molokai, and for north facing shores
of Maui.

High Surf Warning from noon Friday for west facing shores of the Big
Island.

Small Craft Advisory starting 600 AM Friday for all coastal waters
except the Pailolo Channel and Maalea Bay for large combined seas.

&&

Donaldson