Small Craft Advisory 2, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
338 PM HST Fri Jan 11 2019

.SYNOPSIS...
A weak background east to southeast flow will allow daytime sea
breezes and overnight land breezes to dominate through the middle
of next week. The atmosphere will remain stable and somewhat dry.
Showers will favor windward portions of the Big Island and Maui,
while the rest of the state experiences afternoon clouds and a few
showers over interior areas and the terrain. A front may move down
the island chain late Thursday and Friday.

&&

.DISCUSSION...
The islands remain under a stable and weak east to southeast low
level flow that is leading to a dominant land and sea breeze
weather pattern. The subtropical ridge continues to be depressed
south of its normal position, placing the feature just north of
the state, while a strong ridge aloft is anchored overhead. The
result is a stable, mainly gentle east to east-southeast
background flow with a solid inversion based between 5,000 to
7,000 ft. Nearby low level moisture is running near to slightly
below January normal. This has resulted in light shower activity
along windward slopes of the Big Island and east Maui, where
trades are strongest. Elsewhere, sea breezes have produced
afternoon clouds and only a few showers over island terrain.

Little change is expected through the middle of next week. The
subtropical ridge will remain near or just north of Kauai, keeping
the east to southeast background flow weak, and the ridge aloft
will maintain stable conditions. No significant areas of low level
moisture are being detected by the forecast models. As a result,
a land and sea breeze pattern will dominate over most islands,
leading to clouds and a few showers over island terrain and
interior areas followed by clearing at night over most areas.
However, stronger trade winds over the southern end of the island
chain will likely continue to produce showers over windward
portions of the Big Island and east Maui.

A front may move down the island chain late Thursday and Friday.
Recent runs of the GFS and ECMWF have been relatively consistent
in advertising this pattern shift. Southwesterly winds may become
breezy ahead of the front on Thursday, with showers likely
affecting each island as the front moves through. Breezy north to
northeast winds may fill in behind the front.

&&

.AVIATION...
Light winds will prevail across the state through tonight, with
daytime sea breezes and overnight land breezes expected in most
areas. A few light showers could affect windward coastal areas
overnight into the early mornings, and the interior and mountain
areas during the afternoons/early evenings. Brief MVFR cigs/vis
are possible in showers, but VFR conditions will prevail statewide
for the majority of the next 24 hours.

No AIRMETS are currently in effect, and none are expected through
tonight.

&&

.MARINE...
A ridge just north of the islands will keep light easterly to
variable winds over the area into next week. Winds will veer out
of the south by midweek as a front approaches the island from the
northwest.

The current small to moderate north-northwest swell has started to
show a gradual trend down. This swell should hold around 4 to 5
feet, 12 sec through the night, before the next very large
northwest swell arrives.

The new, very large northwest swell is expected to rise rapidly
very early Saturday morning and peak Saturday evening around 13
to 15 ft, 19 sec. This will translate to H1/3 surf height values
25 to 35 ft. Warning level surf will then hold into Sunday. A High
Surf Warning will go into effect by 6 am HST Saturday morning for
north and west facing shores of Niihau, Kauai, Oahu, and Molokai,
and north facing shores of Maui. A High Surf Warning will go into
effect for the west facing shores of the Big Island by 6 pm HST
Saturday.

Combined seas will also rise rapidly as the swell arrives and
spreads down the island chain. A Small Craft Advisory for seas
will go into effect for all waters, excluding Maalea Bay, the
Pailolo and Alenuihaha Channels, and leeward Maui County waters by
6 am HST Saturday morning.

The National Data Buoy Center experienced a widespread data
outage last night and earlier today. This has delayed the
observations from buoys 51101 and 51001. Communications have been
restored and the buoy data from the missing time frames will
continue to back fill over the next several hours, hopefully
coinciding with the arrival of the long period energy.

This swell is then forecast to begin to subside Sunday, likely
falling to advisory levels by Sunday afternoon. Another
reinforcing moderate to large northwest swell is forecast arrive
late Sunday night, keeping surf along exposed north and west
shores at advisory levels into the middle of next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning from 6 AM Saturday to 6 PM HST Sunday for
north and west facing shores of Niihau, Kauai, Oahu, and for
north facing shores of Maui.

High Surf Warning from 6 PM Saturday to 6 PM HST Sunday for west
facing shores of the Big Island.

Small Craft Advisory from 6 AM Saturday to 6 PM HST Sunday for
Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-
Kaiwi Channel-Maui County Windward Waters-Big Island Windward
Waters-Big Island Leeward Waters-Big Island Southeast Waters.

&&

DISCUSSION...Wroe
AVIATION...TS
MARINE...