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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 121958
Area Forecast Discussion
National Weather Service Honolulu HI
958 AM 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 end of the week, with lighter trades
holding through Friday, then becoming breezy next weekend.
Our typical breezy trade wind weather will hold through today
with some scattered showers over windward and mauka areas. Leeward
areas with the exception of the Kona area will remain mostly dry
and sunny for the rest of the day today.
An upper level low currently located about 550 miles north of Big
Island will begin to inch closer and will likely bring some
periods of enhanced moisture during the first half of the week.
Beginning tonight, a slight increase of showers are expected
across windward and mauka areas as a weak disturbance passes north
of the islands. This weak disturbance is expected to pass north
of Oahu Monday morning and move near Kauai by mid day. So overall,
some light to moderate rain showers will be on the increase for
Maui County and the Big Island tonight, Monday morning for Oahu
and in the afternoon for Kauai. Trade winds will remain fairly
breezy through the day Monday, but some fluctuations are expected
particularly for Oahu and Kauai as this weak disturbances passes
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
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.
Long story short, very little weather impacts are expected
through the first half of the week, but an increase of clouds and
showers are expected.
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 Thursday.
Seas will remain well below the 10 foot SCA threshold throughout
the forecast period.
Surf heights are expected to remain on the small side through the
weekend and on through most of next week. There will be a series
of small southerly swells that will keep surf near of just above
background levels. A slightly larger long period south swell may
fill in around Friday. 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 AM HST Monday 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