High Surf in Hawaii, March 6 to 10, 2018

Area Forecast Discussion
National Weather Service Honolulu HI
940 AM HST Tue Mar 6 2018

.SYNOPSIS...
A dissipating front near the islands will fuel windward showers
today, with some decrease in showers expected overnight and
Wednesday as cool air spreads over the islands. Otherwise, moderate
to locally breezy northeast trade winds are expected through the end
of the week, bringing periods of clouds and showers that will
primarily affect windward areas. Fewer showers are expected over the
weekend, as trade winds continue.

&&

.DISCUSSION...
Strong high pressure will prevail to the distant NW of the islands
into the weekend, supplying the islands with cool NE trade winds
while delivering periods of clouds and showers that will favor
windward slopes and coasts.

A weak and diffuse cold front near the islands is in the process of
dissipating and becoming increasingly difficult to identify in
satellite imagery. However, radar shows the associated moisture is
fueling an increase in showers moving over the islands in a locally
breezy ENE trade wind flow. The dissipating front is associated with
a low about 1500 miles NE of the islands while the trade winds are
being supported by a strong 1041 mb high centered about 1800 miles
to the NNW. Moisture associated with the front will likely stall
near windward Big Island tonight and Wednesday, keeping showers
active there, while showers decrease elsewhere across the chain.

The general layout of weather features will change only slightly the
next couple of days, with moderate to locally breezy NE trade winds
delivering dew points in the mid- to upper-50s and loosely organized
bands of clouds and showers that will primarily affect windward
areas. GFS indicates shallow bands moving over the islands Wednesday
night and again Thursday, with another band possible on Friday.

A longwave trough aloft will extend over the islands from the NE
beginning Wednesday, and while it is not expected to significantly
destabilize the island atmosphere, it will help to support the
aforementioned trade wind showers through Friday. This trough will
also bring periods of mid-and high-level cloudiness to portions of
the state. As the trough swings E late in the week, trade wind
showers should become less active over the weekend, but some high
clouds may linger.

High pressure to the NW will move SE late in the weekend and early
next week, and trade winds will veer to the E while the the air mass
moistens. GFS and ECMWF both indicate a significant increase in
moisture Tuesday and Wednesday that could potentially fuel more
widespread rainfall, with trade winds continuing to focus showers
over windward areas.

&&

.AVIATION...
High pressure far north of the area will continue to produced
moderate to locally strong trade winds over the islands. AIRMET
TANGO for low level turbulence remains posted over and immediately
south through west of the mountains. Winds are expected to ease
slightly tomorrow, likely eliminating the need for the low level
turbulence AIRMET.

A dissipating frontal band, running northwest to southeast over
Kauai and Oahu, will continue to push south over the islands today.
Most clouds and showers will focus along the windward and mountain
areas, introducing reduced VIS and CIGS. Some showers will make it
to leeward areas. AIRMET SIERRA is already posted across the
windward and mountain areas of all islands, excluding Lanai. The
frontal band is currently just reaching the Maui County islands, and
is expected to reach the Big Island by this afternoon. Improving
conditions over the smaller islands should begin this afternoon,
with remnants of the front lingering across windward areas of the
Big Island and eastern Maui into tonight.

AIRMET TANGO for upper level turbulence is also posted over the area
due to an upper level jet just south of the islands.

&&

.MARINE...
A Small Craft Advisory (SCA) remains posted for the windier
locations around Maui and the Big Island. The SCA also includes the
windward zones, Kaiwi Channel, and all other waters around Kauai for
large combined seas due to rising northwest and north-northeast
swells. These conditions will continue into mid-week, so the SCA has
been extended through tonight.

Surf will be on the increase today as a larger swell from the north-
northeast continues to build. Surf is expected to reach advisory
level on east facing shores today. The swell may also be large
enough to include north facing shores in an advisory, but for the
moment it appears surf will remain just below the advisory level
there. This swell and elevated surf are expected to last into the
weekend, with a small dip tonight through Wednesday night, due to
the long fetch directed toward the islands from a low far northeast
of the state. In addition, a moderate, long- period west-northwest
swell is expected to build today and persist through Wednesday.
However, surf is expected to remain below the advisory level for
west facing shores. Otherwise, small southerly swells will continue
through Wednesday.

See the latest Oahu Surf Discussion (SRDHFO) for additional details
on surf and swell.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Thursday for East facing
shores of Kauai Oahu Molokai Maui and the Big Island.

Small Craft Advisory until 6 AM HST Wednesdaty for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu
Windward Waters-Kaiwi Channel-Maui County Windward Waters-Maalaea
Bay-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters-Big Island Southeast Waters.

&&

DISCUSSION...Birchard
AVIATION...EATON
MARINE...TS