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Hawaiian Islands Synoptic Discussion and Guidance

231
FXHW60 PHFO 250133
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
333 PM HST Wed Feb 24 2021

.SYNOPSIS...
Breezy to locally strong easterly trade winds will prevail
through the weekend, with clouds and showers favoring windward
and mountain locations. A modest increase in moisture moving in
from the east combined with an upper disturbance may lead to
better windward shower coverage Thursday night through the
weekend. A return of drier trade wind conditions will be possible
early next week.

&&

.DISCUSSION...
Breezy to locally strong trade winds will continue through the
weekend in response to strong high pressure (1040-1050 mb) far
northeast of the state. Clouds and showers will favor windward and
mountain locations, especially through the overnight and early
morning periods. Lowering upper heights combined with a slight
increase in moisture shifting into the area from the east will
support better windward shower coverage Thursday night through the
weekend. Although confidence remains low, this added instability
and better moisture source could trigger a thunderstorm or two
over the Big Island Friday into the weekend - mainly through the
afternoon periods across the leeward Big Island slopes. For the
smaller islands, expect some showers to spill over into leeward
locations due to a combination of the strong trades and the trade
wind inversion rising. A more typical trade wind pattern will be
possible beginning early next week, as drier air arrives from the
east.

&&

.AVIATION...
MVFR clouds that were present this morning have lifted early this
afternoon as locally strong easterly trade winds have allowed
isolated showers to favor east facing slopes and coasts of the
islands. These locally strong winds will continue tonight and into
the day tomorrow as the surface high northeast of the state
strengthens. Clouds and showers will continue to favor eastern
sections of the islands throughout the period. Some MVFR
conditions and mountain obscuration will be possible during the
early morning hours, particularly for the Big Island.

AIRMET Tango remains in effect for low level mechanical turbulence
for areas over and immediately south through west of mountains due
to the locally strong trade winds. Given the persistence of the
strong winds, the threat of low level mechanical turbulence is
likely to persist throughout the forecast period. Occasional low-
level wind shear may also be possible for some airports, but
confidence remains too low to include in the TAFs at this time.

&&

.MARINE...
Strengthening high pressure northeast of the state will produce
strong- to near gale-force easterly trade winds across most of
the Hawaiian waters. The exception will be over the Alenuihaha
Channel, where gales are expected through Thursday. Thus,a Gale
Warning remains in effect for the Alenuihaha Channel through
Thursday afternoon. A Small Craft Advisory is in effect for rest
of the coastal waters due to a combination of strong trades and
elevated seas. Strong trades and elevated seas will likely
continue through the weekend as another strong high builds far
north of the state on Sunday.

Strong trade winds over and upstream of the islands will keep
advisory level surf in place along east facing shores through the
first half of next week. A High Surf Advisory (HSA) is in effect for
east facing shores of Kauai, Oahu, Molokai, Maui and the Big
Island through 6 AM Monday morning. An uptick in surf is expected
over the next few days as the winds increase locally and upstream
of the state.

A series of small overlapping northwest swells will move through
the area into next week, with surf remaining below advisory levels
along exposed north and west facing shores. The first of the
series of northwest swells is expected late Thursday followed by
another reinforcing northwest swell late Saturday into Sunday.

Wrapping trade wind swell continues to provide some small surf
along south facing shores. A small out of season south swell will
give a boost to south shore surf late Thursday through Saturday.

&&

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

Wind Advisory until 6 PM HST Thursday for Molokai-Kahoolawe-Maui
Windward West-Maui Leeward West-Maui Central Valley-Windward
Haleakala-Leeward Haleakala-South Big Island-Big Island North
and East-Kohala-Big Island Interior.

Small Craft Advisory until 6 AM HST Friday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Maalaea Bay-
Pailolo Channel-Big Island Windward Waters-Big Island Leeward
Waters-Big Island Southeast Waters.

Gale Warning until 6 PM HST Thursday for Alenuihaha Channel.

&&

$$


DISCUSSION...Gibbs
AVIATION...Vaughan/Burke
MARINE...Kino

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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