Drought in Hawaii, November 1 to 10, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Sat Oct 31 2020

.SYNOPSIS...
Light and variable winds will continue through Sunday as a low
pressure system north of the islands keeps the large scale winds
weak. As the low drifts further north away from the islands from
Sunday night to Monday a weak high pressure ridge fills in over
the region. Light to moderate trade winds will develop from Monday
through Wednesday with isolated to scattered showers favoring
windward and mountain areas. Another low pressure system will
deepen northwest of Kauai from Wednesday to Friday, wind
directions will become more southeasterlies. The dynamics and
instability around this low will remain too far north for
significant impacts on Hawaiian weather.

&&

.DISCUSSION...
The big picture satellite imagery looks fairly stable across the
Hawaiian Islands this evening. Mostly isolated showers are
developing in the coastal waters near Kauai. A large low pressure
system far north of the islands continues to move away from the
state allowing a weak high pressure ridge to take its place over
the region.

Light and variable large scale winds on Sunday will translate into
land and sea breezes over the islands. A weak subtropical ridge
will slowly fill in over the state, spreading light to moderate
trade winds across the islands from west to east from Sunday
afternoon through at least Wednesday. Isolated to scattered shower
activity will then favor windward and mountain areas, with the
higher rainfall coverage in the overnight to early morning hours.

A slow moving cold front lingering just north of the ridge will
slowly drift southward. Cold air advection associated with this
front will keep the ridge weak near the islands. A migratory high
moving southeast out of the polar region will trap this cold air
and cause a cut off low to form over the weakening frontal
boundary northwest of Kauai by Wednesday. The island by island
forecast from Wednesday onward will depend heavily on the position
and strength of this cut off low relative to the island chain.
Some uncertainty remains in the long range forecast as the closer
this system gets to the northwest islands of Kauai and Oahu the
higher chances for rainfall activity. For now, weather guidance
remains in fair agreement keeping most of the instability and
dynamics northwest of the state with limited weather impacts in an
easterly trade wind regime. Stay tuned.

&&

.AVIATION...
A weakening front approaching from the northwest will keep a light
wind regime in place during the next 24 hours, featuring overnight
land breezes and daytime sea breezes. VFR conditions are expected
to prevail in most areas, although some MVFR cigs may affect PHLI
after 20Z Sunday as moisture associated with the decaying front
moves in.

&&

.MARINE...
Weakening low pressure located a little over a thousand miles
north of the islands is continuing to lift northeast away from
the state tonight. High pressure northwest of the chain will fill
in the low's void and will build in north of the islands through
Monday. The ongoing light to gentle west to northwesterly wind
field surrounding the state will veer more north to northeast
Sunday, while light winds remain variable around the Big Island.
High pressure building into the north will re-introduce long
absent trade flow by Monday. Trades may veer more southeasterly
across the Kauai and Oahu waters at mid week as the next storm
system south of the Aleutian Islands approaches from the northwest.

As the current north-northwest swell subsides tonight, a newly
arriving northwest swell will begin to rise Sunday. This will
produce near November average north shore surf by Sunday afternoon.
Swells will come in from the north to northwest on Monday and may
increase in height. Forecast 7 foot, 14 second period swell will
be pushing north-facing shoreline surf to near High Surf Advisory
levels both Monday and Tuesday. This swell will decline at mid
week, followed by a similarly-sized swell Wednesday night and
Thursday.

South-facing shore surf will remain small into early next week but
will push surf to possibly above summertime averages into mid
week. A mix of small, long period late season background southerly
swells will be the product of ongoing gales within the far
southern hemispheric latitudes. Expect continued small surf along
east-facing shores this weekend. Returning trades will have east-
facing shoreline surf, mainly wind driven waves, trending upward
the next couple of days. This surf may near November averages by
Thursday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

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