High Surf in Hawaii, November 10 to 12, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
318 AM HST Tue Nov 10 2020

.SYNOPSIS...
High pressure north of the state will keep breezy trade winds
blowing through the week, with particularly windy conditions
expected Wednesday and Thursday. Showers will favor windward and
mauka areas with a stray shower spilling leeward from time to
time. An upper level trough moving over the islands may enhance
trade showers Friday through the weekend, while also easing the
trade winds to moderate levels by Sunday.

&&

.DISCUSSION...
Currently at the surface, a 1034 mb high is centered around 1350
miles northeast of Honolulu, while a broad trough of low pressure
is located around 850 miles west of Kauai. The resulting pressure
gradient is producing moderate to breezy trade winds across the
island chain early this morning. Infrared satellite imagery shows
mostly cloudy skies over Kauai and windward Big Island, with
partly cloudy skies in most other areas. Radar imagery shows
numerous showers affecting windward Big Island, with scattered
showers affecting windward sections of the smaller islands. Most
leeward areas are rain free, with a stray shower making the trip
over the mountains from time to time. Main short term concern
revolves around trade wind trends during the next few days.

Strong high pressure northeast of the state will increase trades
to breezy levels across the entire state today. The trades should
ramp up to windy levels late tonight as the high builds due north
of the islands, with windy conditions holding in place through
Thursday. A Wind Advisory may eventually be required for portions
of the state during the peak of the trades. The trades should
trend downward Friday through the weekend as high pressure north
of the islands weakens, with breezy trades on Friday lowering to
moderate levels by Sunday. The trades appear to ramp back up to
breezy levels early next week.

As for the remaining weather details, a band of low clouds and
showers will keep windward Big Island soggy this morning, with
some improvement expected this afternoon. Elsewhere, fairly
typical trade wind shower activity is expected today with showers
favoring windward slopes and coasts. This typical trade wind
weather is expected to hold in place through the weekend and into
early next week. Showers will continue to favor windward and
mauka areas, but due to the strength of the trades, showers will
also reach leeward areas at times. An upper trough is forecast to
move over the islands late in the week through the weekend, and
this could act to enhance showers a bit.

&&

.AVIATION...
A strong high pressure system north of the Hawaiian Islands will
spread breezy to locally strong trade winds across the state for
the next few days. Expect passing showers with cloud ceilings over
windward and mountain areas, brief periods of MVFR ceilings will
also occur in these areas, especially in the overnight to early
morning hours.

AIRMETs are in effect for Tempo Mountain Obscuration for the Big
Island. Expect low level turbulence south and west of mountains
over all islands.

&&

.MARINE...
The center of broad surface high pressure located far northeast
of the islands will be moving south and west through mid week.
The positioning of this high has created a tight enough pressure
gradient across the local waters to generate and maintain
widespread Small Craft Advisory (SCA) level trades into the
second half of the week. The SCA has been expanded to cover all
of the Hawaiian waters and will be in effect through Thursday 6 PM
HST.

Seas will be dangerously rough and choppy under these strong
trades. A High Surf Advisory (HSA) has been extended through
Thursday afternoon for all east-facing shores as the surf will
remain elevated. Breezy trades are expected to diminish Friday
and this will scale down the areal coverage of the SCA with
lowering east-facing surf below advisory levels.

A series of northwest swells are on the schedule this week. A
small, short period northwest swell is slated to peak today with
a slow drop through tonight. The arrival of a moderate longer
period northwest swell Thursday night is forecast to peak on
Saturday with a slow decline through Sunday. South-facing shore
surf will be on the small side for the majority of the week
despite a couple of new long period south to south-southwest swell
arrivals.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Thursday for Kauai Windward-
Oahu South Shore-Oahu Koolau-Olomana-Molokai Windward-Maui
Windward West-Windward Haleakala-South Big Island-Big Island
North and East.

Small Craft Advisory until 6 PM HST Thursday for all Hawaiian
waters-

&&

DISCUSSION...Jelsema
AVIATION...Bohlin
MARINE...Blood