Mauna Kea Weather Center - National Weather Service Bulletins

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Hawaiian Islands Synoptic Discussion and Guidance

525
FXHW60 PHFO 291336
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
336 AM HST Thu Oct 29 2020

.SYNOPSIS...
A front over Maui County will stall and dissipate by tonight.
Spotty heavy showers will continue along and southeast of the
front. Northwest winds behind the front will bring less humid
conditions and will push shallow shower bands over the islands
through the weekend. A ridge will build north of the islands by
Monday and bring a return of trade winds.

&&

.DISCUSSION...
A front stalled over Maui County will weaken over the next 24
hours. Showers will likely remain concentrated along the weakening
front, but locally breezy westerly winds will also bring a few
showers to most islands, especially along leeward (west facing)
slopes. Tomorrow, these winds could become gusty over some
windward (east) areas as the winds blow downslope. There will
noticeably drier air behind the front.

During the weekend, the low will lift off to the northeast. Northwest
to north flow south of the low will continue to carry bands of
showers over the islands. A trough aloft digging south over the
area could enhance showers on Sunday.

The global models are in good agreement showing a surface ridge building
north of the islands by Monday. The ridge will produce easterly
trade winds over the islands.

&&

.AVIATION...
Clouds and showers developing along a ENE-WSW front draped over
Maui County have been generally diminishing in coverage and
intensity overnight as the front becomes increasingly diffuse.
However, the front is still expected to produce isolated IFR
VIS/CIG and TEMPO MVFR VIS/CIG through the morning, with the
potential for IFR conditions expected to diminish by afternoon. In
the meantime, AIRMET SIERRA for mountain obscuration remains posted
for Maui County. A stable post-frontal NW flow over Kauai and
Oahu will bring low clouds and a few showers, mainly to the N and
W facing slopes while low clouds and a few showers will develop
in the SW-W flow near the Big Island. The front will gradually
dissipate while low pressure N of the islands supports low-level
winds from the W statewide into Friday.

&&

.MARINE...
A weakening front near east Maui will likely stall and gradually
dissipate in the vicinity of the northern Big Island later today
and tonight. 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 from Friday into the weekend as a surface low remains
north of the state, and a surface trough moves across the western
islands from the north-northwest. Trade winds may return from
late Sunday into early next week as a surface ridge builds north
of the state.

A new moderate short-period north-northwest swell due to the
fetch associated with the surface low located north of the
islands is expected to arrive later this morning. This swell will
gradually build from this afternoon through Friday, which will
cause surf to increase over 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 small short-period southeast swell, as well as
small long-period south and southwest swells. An upward trend in
surf along south facing shores is possible next Wednesday due to a
slightly larger long-period south swell. The current northeast
swell will continue to steadily trend down today. Another small
medium-period northeast swell arriving tonight or Friday will
maintain tiny surf along east facing shores into this weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory till 6 PM Friday for the summits of Mauna Kea and
Mauna Loa on the Big Island.

&&

$$
DISCUSSION...Donaldson
AVIATION...Birchard
MARINE...Houston

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

Current Conditions
Temp		-0.7 C
RH		99 %
Wind		WSW 36 mph
Road		Closed