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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 130201

Area Forecast Discussion
National Weather Service Honolulu HI
401 PM HST Sun Jul 12 2020

Moderate to locally breezy trades will continue through Monday,
with an increase in trade showers expected beginning tonight as
an upper level low nears the state. A more active shower pattern
will hold through the middle of the week as the trade winds ease
into the light to moderate range. A more typical trade wind shower
regime will return for the weekend with lighter trades holding
through Friday, then becoming breezy next weekend.


An upper level low currently located about 550 miles north of the
Big Island will be slowly moving west over the next few days and
will likely bring some periods of enhanced moisture during the
first half of this week. Beginning tonight and into Monday, a
slight increase of showers are expected across windward and mauka
areas as an area of higher moisture passes near the islands.
Latest radar and satellite imagery are already showing an uptick
in showers over windward Oahu and Kauai this afternoon. This trend
will continue overnight tonight, with the greatest moisture
passing near the western half of the state into Monday. Some
moderate rain showers are expected to ride in with the breezy
trade winds over windward areas through Monday. Leeward areas
could see some passing showers particularly during the overnight
and early morning hours.

Starting Tuesday, the high currently located far north-northeast
of the state will begin to drift further east and away from the
state. This will allow the trades to weaken to light to moderate
speeds and will remain through much of the upcoming work week.
Another round of some enhanced moisture is possible Monday night
into Tuesday.

By the middle of the week, the upper level low will begin to drift
further west and a drier air mass will begin to move in from the
east. This should bring back our fair trade wind weather to the
eastern half of the state on Wednesday, while some clouds and
showers continue to linger over the western half of the state.
Thursday looks to be the sunniest day of the week with light trade
wind weather. For Thursday night and Friday, latest guidance is
showing another disturbance passing near the state which may bring
an increase of clouds and showers toward the end of the week. By
the weekend, model guidance are in fairly good agreement with
breezy trade wind weather returning.


High pressure to the north will maintain a moderate to locally
breezy trade wind pattern over the region through tomorrow. An
upper level low to the northeast could enhance some of the trade
wind shower activity that will be focused over windward and
mountain areas. VFR conditions are expected to prevail, with some
periods of MVFR in clouds and showers. Greater chance for MVFR
conditions tonight and tomorrow as upper level low moves closer
to the region.

AIRMET Tango remains in effect for mechanical turbulence to the
lee of the islands. Expecting this AIRMET to remain in place for
another day or so with the locally breezy trades in place.

No other AIRMETs expected today, however as alluded to above, an
AIRMET for mountain obscuration is possible tonight or tomorrow
with clouds and showers moving in.


High pressure far to our north-northeast is providing for breezy
trade winds across the area. A Small Craft Advisory (SCA) is
currently posted for the typically windy waters around Maui County
and the Big Island. The high is forecast to drift eastward over
the next couple of days with a gradual decrease in trade wind
speeds expected by Tuesday. The SCA will likely be discontinued by
then. These lighter trade winds will continue through Friday.
Seas will remain well below the 10 foot SCA threshold throughout
the forecast period.

There will be a series of small southerly swells over the next
several days that will keep surf near of just above background
levels. A slightly larger long period south swell may fill in
Friday and Saturday. East facing shores will continue to experience
short period choppy surf produced by the trade winds. A small but
slightly longer period east swell produced from Tropical Cyclone
Cristina far in the eastern Pacific, may provide a slight uptick
in surf heights during the late Tuesday through Friday time
period. No other significant swells are expected.


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



AVIATION...M Ballard

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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