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Temp1.2 C
RH16 %
WindNE 4 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 250647

Area Forecast Discussion
National Weather Service Honolulu HI
847 PM HST Sun Jun 24 2018

A high pressure ridge north of the islands will keep a breezy
trade wind weather pattern across the Hawaiian Islands through
next week. Clouds and showers will move across each island
favoring windward and mountain areas with brief periods of showers
drifting over leeward sections. Wind speeds will decrease next
weekend as an upper low weakens the ridge north of the islands.


A strong high pressure ridge north of Hawaii will continue to
produce breezy trade winds through Friday. Trade wind inversion
heights are high enough to continue to produce showers across all
islands with likely showers favoring windward and mountain areas
with brief periods of showers drifting into leeward areas through
the week. Longer range models continue to show good agreement on
this high confidence breezy trade wind solution.

A weak upper level low shown on GOES water vapor imagery remains
just northeast of the islands and this system will drift slowly
westward reaching the eastern half of the state as an upper level
trough on Monday. This system is fairly weak and will not deliver
much noticeable weather impacts as the trade wind inversion
height is already high enough for sustained shower activity.

In the extended forecast period, the ridge north of the islands
will weaken next weekend in response to a strong upper level low
approaching the islands from the north. Lighter trade winds may
allow sea breezes to develop along western slopes of all islands
each afternoon.

Vog (Volcanic smOG) and other emissions from Kilauea and the East
Rift Zone will drift southwest across the Kau District with
atmospheric eddies west of the Big Island helping to push some vog
concentrations up along leeward slopes of the Big Island. However
the rest of the state will remain well protected from vog
emissions by the breezy northeasterly trade winds keeping the vog
plume well south of the smaller islands through Saturday.


Breezy, occasionally strong, trade winds will persist as a ridge
of high pressure remains northeast of the state. AIRMET Tango
remains in effect for low level turbulence over mountains and
leeward sections of all islands due to the breezy trades. AIRMET
Tango may continue over the next couple of days due to the
persistent wind speeds.

AIRMET Sierra is in effect for tempo mountain obscurations
this afternoon for windward sections of Kauai, Oahu and the Big
Island, which may be extended through morning for some windward
sections. Elsewhere, VFR conditions will prevail with passing low
clouds and showers bringing isolated MVFR conditions to windward
and mauka sections.


Fresh to strong trades associated with high pressure to the
NE will continue through the week, with some decrease in wind
speeds possible next weekend as the pressure gradient potentially
weakens. A Small Craft Advisory for the windier areas around Maui
County and the Big Island is in effect through Tuesday night, but
an extension in time will likely be required.

Surf along E facing shores will remain elevated the next couple of
days due to the local and upstream trade wind flow, with surf
heights remaining below advisory levels. Surf along S facing
shores will increase starting Tuesday as a long-period S swell
arrives. The peak of the swell around Thursday will likely warrant
a High Surf Advisory, with the swell gradually diminishing into
next weekend. A S hemisphere storm track that is favorable for
the generation of another S swell is expected the next couple of
days, with associated swells potentially arriving about a week


Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.




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