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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 200150

Area Forecast Discussion
National Weather Service Honolulu HI
350 PM HST Mon Oct 19 2020

A weakening frontal boundary will linger near Kauai over the next
several days. Clouds and passing showers will favor the west end
of the island chain for the next couple days with drier conditions
expected elsewhere. A bit drier weather is expected Wednesday
through Friday. The front may strengthen a bit over the weekend
with increasing clouds and showers mainly for Kauai.


A stalled and weakening frontal boundary lies near Kauai.
Moisture associated with the front is providing for passing
showers over Kauai and Oahu as well as over the adjacent coastal
waters. Showers are generally moving from south to north. Most
showers are generally on the light to moderate with a few embedded
heavy showers seen on radar. Most of Maui county and the Big
Island are dry. Winds are southerly over the west end of the
island chain with light east to southeast flow around the Big

The frontal boundary will remain near or just west of Kauai over
the next several days and continue to weaken over time. Showers
will continue to favor Kauai and possibly Oahu during this period
with much less in the way of shower activity over the rest of the
the state. The airmass will become a bit drier from midweek onward
so it will not feel quite as muggy. Winds will continue to remain
light across the area favoring an east to southeast direction with
local land and sea breezes dominating in sheltered locations.

As we head into the weekend, the old frontal boundary may get
some reenforcement energy. Some increase in showers is likely
over and around Kauai if this were to occur. Winds will continue
to remain on the light side favoring an east southeast direction
with daytime sea breezes and nighttime land breezes occurring in
sheltered locations.


A north to south front remains hung up around Kauai and Niihau,
but is forecast to dissipate by Wednesday. However, with some
lingering upper-level support, expect periods of showers to
continue developing over the western half of the island chain.
Cloud tops with these showers are mostly around 10-15kft, with
some higher tops to 20-25kft possible. Though more cloud cover is
in place over the Kauai and Oahu area, most ceilings are above
3000 ft MSL and no AIRMETs are needed at this time.

Surface winds will remain light to moderate out of the southeast
for the Big Island and Maui County, and light out of the south for
Oahu westward.


Light to moderate southerly winds and showery conditions will
continue over the Oahu and Kauai waters as a stalled frontal
boundary slowly diminishes through midweek. For Maui County and
the Big Island, drier conditions along with light to moderate
east to southeast winds will prevail with pockets of fresh breezes
possible in the channels and windier areas with this direction.
Although wind directions should shift back out of the east through
the second half of the week, wind speeds should remain light
enough for land and sea breeze conditions to continue near the
coasts as low pressure remains northwest of the islands.

Nuisance coastal flooding due to a combination of peak monthly tides
and water levels running near a foot above predicted will continue
through Tuesday. Impacts are anticipated around daybreak when the
peak daily tides occur. See the latest Special Weather Statement
for more details regarding impacts. Daily tidal ranges will lower
through the second half of the week.

Surf along north and west facing shores will continue to lower into
Tuesday as the northwest swell that peaked over the weekend eases.
Outside of a small east-northeast swell that will impact exposed
north facing shores Tuesday through midweek, very little is
expected. Guidance shows a gale developing over the far northwest
Pacific near the western Aleutians Tuesday night into Wednesday,
then tracking east-northeastward into the Bering Sea through the
second half of the week. A large area of strong- to gale-force
winds on the backside of this feature focused at the islands
within the 315 to 335 degree directional bands are predicted with
seas responding and climbing to around 25 ft in this area. If
this materializes, expect a long-period, northwest swell locally
to fill in late Saturday into Sunday. More details will follow as
the scenario evolves.

Surf along east facing shores will trend up Tuesday through
Thursday as an east-northeast swell arrives from a recent batch
of strong breezes that were focused at the islands near the west
coast over the weekend. Otherwise, small surf will continue due to
the lack of trades.

Surf along south facing shores will remain small through the week
with mainly a combination of background south and south-
southeast swell energy moving through.






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

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It was last modified on: Wed, Dec 17 2014 - 1841 UTC
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