Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 271955

Area Forecast Discussion
National Weather Service Honolulu HI
955 AM HST SAT AUG 27 2016

Locally breezy trade winds will continue through early next week as
high pressure persists north of the state. Passing showers will
favor windward and mauka areas, with showers more active tonight
through Sunday night. By the middle of next week, we may begin to
feel impacts from Tropical Storm Madeline.


Water vapor imagery shows an upper level ridge north of the state,
with a low far to the northwest. At the surface, high pressure is
located far to the north, with a ridge extending to the south-
southwest. 12z soundings show inversion heights ranging from just
over 7kft at Lihue to near 9kft at Hilo. Precipitable waters are
1.18 and 1.37 inches respectively, which is below average for this
time of year. Early morning MIMIC total precipitable water imagery
shows a sharper gradient across the state, with lower values over
Kauai and higher values near the Big Island. A bulge of tropical
moisture is located near 150W, with a bigger surge of moisture
located just east of 140W associated with Madeline.

Trade winds will be the dominant feature for the next few days.
Even though the high is far north of the state, a nearly
stationary low to our south will help to enhance the pressure
gradient across the islands. This will lead to locally breezy
conditions, especially from tonight into Monday. Rainfall has
been pretty typical, with the wettest gages receiving a quarter
to a half inch of rain over the past 12 hours. Little change is
expected during the day, with showers more active over the
easterly half of the state and mainly affecting windward and
mauka areas.

An area of showery clouds is located over the northeast offshore
waters, and are expected to spread across the state
tonight/Sunday. High-resolution model guidance shows a surge in
trade winds with this feature, and forecast soundings/cross
sections show an increase in moisture depth. The current forecast
features an increase in trade showers tonight, which looks on
track. Behind this feature, moisture depth starts to decrease
Sunday night, and we may be drier than normal by Monday. Another
surge of moisture to enhance trade showers is possible on
Tuesday, but that is starting to get into the more uncertain
period of the forecast.

The National Hurricane Center in Miami is currently issuing
bulletins on Tropical Storm Madeline, which is located just east
of 140W. Madeline is expected to move northwest for the next few
days before turning west, and may impact the state during the
middle of the week. There is a large degree of uncertainty with
the speed, track, and intensity of tropical systems like this,
which can result in significant changes to the types of impacts we
could see. Be sure to stay up to date with the latest forecasts,
which are issued every six hours. When Madeline crosses 140W into
the Central Pacific Basin this evening, the Central Pacific
Hurricane Center in Honolulu will begin issuing advisories. In
addition, Hurricane Lester is located far to the east, but may
affect the state over the upcoming holiday weekend. Given it`s
more extreme distance, there is even greater uncertainty as to
possible impacts to the state from Lester.


Tradewind moisture will affect mainly windward and mountain areas
this weekend. Currently most of the moisture in the way of low
clouds is located from the Big Island to Molokai. Some MVFR
ceilings and visibilities expected with the clouds and showers
passing through. But overall...VFR conditions will prevail about
the state. Cloud tops are running between 8000 and 10000 feet.
Currently there are no AIRMETS or SIGMETS.


A Small Craft Advisory remains in effect for the typically windier
locations around Maui county and the Big Island, due to locally
breezy trade winds accelerating around the high terrain. Winds
may be somewhat lighter today, but are expected to pick up by
tonight as the cloud feature northeast of the state moves through.

No significant swells are expected through the middle of next week,
though surf along E facing shores will be slightly elevated due to
the stronger trades. Winds and seas, as well as surf along east
facing shores, may increase toward the middle and end of next
week due to the possible effects from Tropical Cyclones Madeline
and Lester. Uncertainty in this forecast scenario is high.


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



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