Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
330 am HST sun may 3 2015
moderate trade winds will persist into Monday...with periods of
breezy trades expected during the upcoming work week. Conditions
will be stable...with clouds and showers favoring windward slopes
and coasts. Pockets of moisture riding in on the trade winds will
periodically boost shower coverage... allowing a few showers to
spread to leeward sections of the smaller islands.
the ongoing forecast remains in line with the latest model
guidance...with a climatological trade wind weather pattern
prevailing for the foreseeable future. Moderate to locally fresh
trade winds will prevail this week...providing brief showers that
will favor windward slopes and coasts.
Moderate trade winds today and Monday will likely increase a notch
on Tuesday. A surface high about 1150 miles NE of the islands is
currently driving the trade winds...but is being weakened by fronts
to its north and west. The high will rebuild by Tuesday...pushing easterly
trade winds into the locally breezy range before dropping a notch on
Wednesday and Thursday as the high weakens. A new high building northwest
of the area late in the week is expected to lead to stronger trades
as we head into next weekend.
Brief showers will favor windward slopes and coasts...with showers
most active during the night and morning hours. Pockets of moisture
passing through will lead to increases in showers at times...but
these are difficult to forecast with much skill beyond the first
period. One such area of moisture riding in on the trades has made
for a wet night along the windward side of The Big Island...with
rain gages indicating 12 hour rainfall totals between one half and
one inch. Probability of precipitation have been boosted over windward Maui and Big Island
through this morning to account for this area. GFS depicts another
shower area passing through Monday night and Tuesday...while other
model guidance is not. As GFS has a decent track record detecting
these showery patches...windward probability of precipitation have been increased for late
Monday and early Tuesday. Either way...midlevel ridging will remain
overhead through the week...keeping the atmosphere rather stable
with the inversion mainly varying between 6000 to 9000 feet.
VFR conditions with moderate to locally breezy trade winds will
prevail across most areas of the state today. MVFR conditions with
areas of mountain obscuration will affect windward sections of The
Big Island and east Maui this morning...where airmet Sierra is in
effect. Conditions should improve in these areas by afternoon.
Isolated MVFR conditions will also be possible across the windward
sections of the other islands...mainly within passing showers.
Airmet Tango is in effect for moderate low level turb over and S
through west of the mountains on all islands...due to the locally breezy
a Small Craft Advisory /sca/ for the typically windy waters around
Maui and The Big Island is in effect through Tuesday...and will
likely need to remain in place through the upcoming week. The Small Craft Advisory
may need to be expanded in area around Tuesday...and again around
Friday...when trade wind speeds are expected to be stronger.
Moderate to fresh trade winds prevailing over and upwind of the
islands through the week will maintain elevated short-period surf
along east facing shores. The expectation is that surf will remain
below advisory levels however. Elsewhere...a long period south-southwest swell
is expected to gradually build on Tuesday and peak Wednesday into
Thursday. Peak surf heights associated with this swell will likely
necessitate a high surf advisory for S facing shores. A tiny north swell
is expected Monday through Wednesday...with a slightly larger north-northwest
swell expected from Thursday into Saturday.
Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay... and
the pailolo and alenuihaha channels...and waters south of The Big
Public and marine...birchard