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Hawaiian Islands Synoptic Discussion and Guidance

435
FXHW60 PHFO 071953
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
953 AM HST Fri Aug 7 2020

.SYNOPSIS...
A typical trade wind weather pattern can be expected through the
weekend and on into the middle of next week thanks to high
pressure far north of the area. Clouds and passing showers will
tend to favor windward and mauka areas with just a few brief
showers expected over select leeward locations.

&&

.DISCUSSION...
Surface high pressure is centered far north of the area. This
places the islands in a moderate to breezy trade wind environment.
Meanwhile, a week mid level low is centered just west of Kauai.
The combination of instability associated with the mid level low
along with an area of enhanced moisture embedded in the trades,
has been providing for passing showers over most windward and
mauka areas this morning with a few brief showers spilling over to
some leeward locations. The mid level low is forecast to drift
westward today with the airmass becoming more stable. Overall,
shower activity is expected to decrease later today.

The area of high pressure will remain to our north through the
weekend and on into the middle of next week. Little day to day
change in wind speeds or direction is expected. Satellite imagery
shows plenty of moisture upstream of the islands. Even though the
airmass will be more stable, this moisture will tend to interact
with island terrain and continue to allow for passing showers over
windward and mauka areas especially during the late night through
mid morning hours with a possible second maximum during the late
afternoon and early evening hours. Models indicate a drier airmass
will be in place early next week but another mid level low may be
in the island vicinity which could keep shower probabilities a
bit elevated especially for windward and mauka areas.

&&

.AVIATION...
High pressure far north of the state will bring persistent
moderate trades to the islands through this morning causing moderate
turbulence in the lee of the mountains. An area of enhanced
moisture and weak instability caught up in the flow will depart to
the northwest today but may still support a greater coverage of
showers for Oahu and Kauai into this evening. Brief MVFR
associated with typical trade wind showers will also be possible
for all windward locations.

AIRMET TANGO remains in effect over and immediately south thru
west of mountains below 9000 feet for tempo moderate turbulence.

AIRMET SIERRA for Kauai through Maui for mtn obsc above 025
is expected to be allowed to expire 22z.

&&

.MARINE...
Breezy trade winds will trend up this weekend as the high north-
northeast of the area strengthens. This will likely result in the
current Small Craft Advisory needing to be extended and expanded
beyond the typically windier waters around Maui County and the Big
Island. Winds are expected to back down again early next week.

The current small south swell will continue to decline today,
with south facing shore surf returning to background levels by
tomorrow. Small short period southeast swell will continue, with
the Big Island blocking some of that energy from reaching the
smaller islands. Surf along east facing shores will build through
the weekend as trade winds strengthen. Although, surf heights
should remain just below the advisory levels along east facing
shores.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

&&

$$

DISCUSSION...Burke
AVIATION...Powell/Clark
MARINE...EATON

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

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RH		32 %
Wind		ENE 12 mph
Road		Open (4x4)