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RH59 %
WindSSW 42 mph
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Hawaiian Islands Synoptic Discussion and Guidance

500
FXHW60 PHFO 300631
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
831 PM HST Thu Oct 29 2020

.SYNOPSIS...
A dissipating front across the Big Island will lift away tonight.
Another weak trough passing by will bring moderate west to
northwest winds through Saturday with some scattered showers.
Rainfall should remain light. A ridge will build north of the
islands by Monday and bring a return of trade wind weather through
most of next week.

&&

.DISCUSSION...
A dissipating front across the Big Island will lift away from the
state tonight. Satellite loop and radar show that associated
clouds and showers are already diminishing across the state, and
this trend is expected to continue Friday. Over the summits of
the Big Island, a Wind Advisory remains in effect, where southwest
winds of 35 to 50 mph are expected through at least Friday
afternoon and possibly through Saturday. Over the western end of
the state, we will continue to see a cooler and drier airmass with
a few light showers possible overnight tonight. A weak trough
will trigger scattered showers across the state on Friday.
Westerly winds will increase behind the trough and could produce
gusty downslope winds on the east side of the islands.

Over the weekend, the trough will lift off to the northeast,
causing local winds to decrease. Light to moderate westerly winds
will continue through Saturday and become light and variable on
Sunday. Winds should be light enough for the development of
afternoon sea breezes on Sunday. This will cause afternoon cloud
build ups, along with some scattered showers, over interior areas
during the afternoon. Also, a weak upper trough digging south
over the area could enhance showers on Sunday.

Models show a surface ridge building north of the islands by
Monday. The ridge will produce easterly trade winds over the
islands through most of next week.

&&

.AVIATION...
A low pressure system roughly 400 miles north of Oahu will keep
light winds in the forecast, with mostly cloudy conditions, and
brief periods of MVFR ceilings for some islands. Isolated to
scattered showers are forecast across the region for the next few
days. A band of low clouds lingers over the east and southeast
slopes of the Big Island, producing MVFR ceilings through the
overnight to early morning hours.

AIRMET Sierra in effect for Tempo Mountain Obscuration over the
east and southeast slopes of the Big Island due to low clouds and
showers.

&&

.MARINE...
A broad surface low is located about 400 nm north of Honolulu
early this evening. This feature is moving slowly south, and the
large circulation around it will continue to affect the waters
near the islands into Saturday. In addition, a dissipating front
remains stalled near the northern Big Island. As a result,
moderate south to southwest winds will persist over the waters
surrounding the Big Island, while light to moderate northwest to
west winds are expected over the waters adjacent to the smaller
islands. This general wind pattern is forecast to continue
through Saturday. In addition, a series of weak disturbances may
move down across the western islands from the north-northwest.
The surface low is forecast to move north-northeast away from the
area from Friday night into Saturday. Trade winds will likely
return to the state from late Sunday into early next week as a
surface ridge builds north of the area.

The surface low north of the islands is sending a north-northwest
swell toward the state early this evening. Recent observations
from the National Data Buoy Center buoys northwest of Kauai
(51001 and 51101) have been indicating the north-northwest swell
may be about 1 foot above the guidance. This swell will continue
to spread down across the island chain through Friday, which will
cause surf to increase along most north facing shores. The
greatest surf heights are expected along northern exposures of
Kauai and Oahu on Friday. This north-northwest swell will
gradually lower from Friday night into the weekend. Forerunners
from a new long-period northwest swell are expected to arrive
late Saturday. This swell will likely build to moderate heights,
and shift out of the north-northwest from Saturday night through
Sunday. Yet another long-period north-northwest swell is expected
to spread across the area from late Sunday night through Monday.
Surf produced by this swell may approach the High Surf Advisory
criteria along some north and west facing shores of the smaller
islands Monday. This north-northwest swell will gradually lower
from Tuesday into mid-week.

Surf along south facing shores will remain small into early next
week due to a mix of southerly swells. An upward trend in surf
along south facing shores is possible next Wednesday due to a
slightly larger long-period south swell. Expect tiny surf along
east facing shores through this weekend. Surf along east facing
shores may trend up slightly early next week as the trade winds
return.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM HST Friday for Big Island Summits.

&&

$$

DISCUSSION...Powell
AVIATION...Bohlin
MARINE...Houston

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office