Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
1005 am HST Thu Oct 20 2016
fresh to strong trade winds will persist through the weekend and
will supply periods of wetter and drier conditions. Trades will
focus more of the rain across windward and Mauka areas, with many
of the showers carrying over to leeward sides of the smaller
islands at times.
a 1033 mb surface high is located about 1100 miles north of Kauai
this morning and is driving fresh to strong trade winds across the
state. A weak cold front is about 400 miles north of Kauai and is
slowly moving towards the south. To the east, an area of clouds
and showers is moving in with the trades, and are currently
between 200 to 300 miles upstream. Meanwhile, conditions are
trending drier across the state this morning as overnight showers
are sliding west of our area. 12z soundings at Hilo and Lihue
showed precipitable water (pw) of 1.3 to 1.5 inches with weak
midlevel inversions. Mimic satellite derived precipitable water shows relatively
drier values of 1.1 to 1.2 inches moving in from the east,
followed by precipitable water values of 1.4 to 1.5 inches associated with the
clouds and showers further upstream.
For today, expect to see mostly sunny skies for leeward areas
while partly to most cloudy skies prevail over windward areas and
the Kona slopes on The Big Island. Showers will be kept to a
minimum due to the drier air filtering in. The upstream showers
are likely reach the eastern end of the state tonight and continue
to track westward across the area on Friday and Friday night. The
breezy trade winds are likely to blow many of the showers onto
leeward sides of the smaller islands. Drier air will again filter
in with the trade winds on Saturday.
Sunday afternoon into Monday, an east to west oriented band of
moisture, remaining from the aforementioned cold front to the
north, will push through the islands by the trade winds. The band
will bring an increase in showers to all parts of the smaller
islands, particularly for windward and mountain areas. The trade
winds will finally weaken behind the remnant around Monday.
After this band exits the islands, models are indicating additional
bands or waves of moisture to move through the islands next week,
making for what appears to be a progressively wet trade wind pattern.
breezy trade winds are producing moderate turbulence leeward of
the mountains, and airmet Tango is posted. This airmet will
likely remain over the next few days. Trades will push clouds and
showers into the windward slopes producing isol MVFR conditions
due to clouds and shra.
a Small Craft Advisory (sca) covers all coastal waters through Sunday
afternoon due to expected strong trade winds. Winds are forecast
to reach near-gale strength in the typically windy areas around
The Big Island and Maui Friday through Saturday. The trades will
start decreasing late Sunday with the areas under the Small Craft Advisory being
scaled back to the typically windy areas by Monday.
There will be a series of mainly small northwest to north northwest
swells into next week, and a small background swell from the
south. The strong trades, along with the upstream fetch, will
build surf for east facing shores beginning Friday. Surf heights
are likely to reach advisory levels from Friday night through
Small Craft Advisory until 6 PM HST Sunday for all Hawaiian