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Temp3.4 C
RH14 %
WindNE 14 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

125
FXHW60 PHFO 160605
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
805 PM HST Sat Jun 15 2019

.SYNOPSIS...
A fairly dry trade wind weather pattern will continue through the
middle of next week. Clouds and isolated to scattered showers will
remain in the forecast over windward and mountain areas favoring
the overnight and early morning hours. Little to no rain is
forecast over leeward areas.

&&

.DISCUSSION...
Another extended period of fairly dry trade wind weather remains
in the forecast through next week. Subtle changes in the strength
and position of the high pressure ridge north of the islands will
result in slight adjustments to trade winds and windward shower
coverage over the next seven days. Expect moderate to breezy trade
winds to continue on Sunday with limited shower activity in a
stable and mostly dry weather pattern.

In the big picture, the subtropical ridge north of the islands
continues to produce moderate to breezy trade winds on Sunday. A
strong high pressure ridge aloft will keep clouds and showers to a
minimum with trade wind subsidence inversion heights around 5000
to 6000 feet. A long wave trough remains anchored over the
Central Pacific basin. Subtle changes in the intensity of this
long wave trough will impact the strength of the ridge north of
the islands, modifying the trade wind direction and speed for the
upcoming work week.

On Monday and Tuesday, the long wave trough deepens weakening the
subtropical ridge north of the islands. These changing large
scale pressure patterns will place the Hawaiian Islands along the
southwestern edge of the surface ridge axis, causing wind
directions to veer towards the southeast direction. At the same
time step, the upper level ridge weakens as a trough drifts over
the state. Wind speeds will weaken slightly on Monday and Tuesday
with modified land and sea breezes forming along sheltered leeward
slopes. The upper trough will decrease atmospheric stability
allowing for more scattered windward and mauka showers favoring
the overnight and early morning hours. Trade wind subsidence
inversion heights will rise into the 7000 to 9000 foot range by
Monday night.

Wednesday through Friday, the surface ridge north of the islands
builds slightly and trade winds back towards a more easterly
direction. The subtropical jet stream will develop over the
islands producing high cirrus cloud ceilings across the state.
A building upper level ridge will bring another round of more
stable conditions with subsidence inversion heights falling back
down into the 5000 to 7000 foot range on Wednesday and Thursday. A
weak upper trough will bring a return to more scattered windward
and mauka showers from Friday night into Saturday morning.

&&

.AVIATION...
Surface high pressure will remain to the northeast of Hawaii,
providing moderate to locally strong trade winds to the area.
Passing low clouds will affect windward and mountain areas of the
islands at times, bringing some showers. Mainly VFR conditions
will prevail, though windward and mountain areas may see brief
MVFR ceiling and VIS.

No AIRMETS are expected through early Sunday, but the potential
for AIRMET Tango for low-level turbulence continues due to the
more robust trade winds.

&&

.MARINE...
High pressure far northeast of the state will maintain fresh to
locally strong trades through the middle of the coming week. Winds
may veer east-southeasterly Monday into Tuesday as a weak trough
develops far west of the state. A Small Craft Advisory (SCA) is in
effect for the typically windy waters around the Big Island and
Maui through early Monday morning. This will likely need to be
extended at least into Wednesday.

Elevated surf is expected along south facing shores through
early Sunday morning. Due to the swell still holding strong into
this evening, the High Surf Advisory has been extended through
tonight. For next week, we should see several reinforcing south-
southwest swells for the first half of the week with surf heights
around the summer average through the middle of the coming week.

A reinforcing northwest swell is filling in tonight and will
continue to produce surf in the small to moderate range along
north facing shores through Sunday. Additional pulses of tiny
northwest swell are expected through next week. Surf along east
facing shores will remain small through the weekend, then rise
early next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Sunday for all south facing
shores.

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

&&

$$

DISCUSSION...Bohlin
AVIATION...Hui
MARINE...Kinel

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