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Area forecast discussion 
National Weather Service Honolulu HI
330 am HST Thursday Oct 2 2014

Synopsis...
light trade winds today and Friday will yield to light and variable
winds over the weekend...continuing into next week. The light trades
will deliver a few showers to windward coasts and slopes...while
also allowing afternoon clouds and showers to develop over interior
and leeward areas. Some showers may be heavy this afternoon. The
light and variable winds over the weekend will lead to mostly clear
nights and mornings...with afternoon clouds and showers favoring
interior and upslope areas. A more stable air mass developing over
the islands should limit shower intensity by the weekend...but muggy
conditions will continue.

&&

Discussion...
it/S been a relatively quiet night...with light trade winds pushing
a few showers ashore along windward coasts and slopes. While radar
shows that some of these small showers have intense cores...coverage
is limited. Latest surface analysis depicts a surface ridge within
100 miles north of Kauai...extending SW from a high centered about 1900
miles NE of the islands. With the ridge in this position...a light east
to southeast flow exists in the low levels...with island-scale land/sea
breeze circulations overriding this flow. A weakening low aloft
centered about 550 miles east-northeast of Oahu is moving slowly east...while an
associated weak trough extends west over the islands. High clouds S of
the trough axis are streaming over The Big Island and adjacent
waters.

A somewhat less active weather pattern is expected to develop over
the islands the next several days...as the low aloft weakens and a
slightly drier airmass moves in from the east. Models indicate that a
weak trade wind flow today will persist through Friday...as the
ridge drifts slightly north. Still expect afternoon seabreezes today and
Friday to drive interior and leeward clouds and showers. Morning
balloon soundings indicate that a moist and unstable air mass
remains in place...with the phli sounding indicating cape values in
excess of 3000 j/kg. Thus locally heavy rainfall appears possible
once again this afternoon...mainly interior and leeward. Showers are
not expected to be as widespread or intense on Friday. High clouds
near The Big Island should trend towards clearing out today as the
trough aloft weakens.

During the weekend and into the middle next week...a cold front
several hundred miles northwest of the state will move slowly southeast...pushing
the surface ridge over the state...supporting a pure land/sea
breeze pattern over the islands. Scattered showers will develop
mainly across interior and leeward areas each afternoon...with
clearing each night as land breezes take over. Developing light southeast
background flow may allow areas of volcanic haze to spread over the
smaller islands during this time. The front is forecast to retreat
northward by the middle of next week...allowing the ridge to shift
north...and a light trade wind flow is expected to return. Warm and
muggy conditions will continue through the forecast period...with
above normal sea surface temperatures contributing to rather high
dewpoints.

&&

Aviation...
VFR conditions and light winds will prevail this morning. Sea
breezes will produce low clouds over the leeward and island interior
sections by the late morning. MVFR ceilings...tempo mountain obscure will be
possible by this afternoon as the clouds build through the day...and
airmet Sierra may be necessary. Instability across the state will
allow for some of the sea breeze driven clouds to produce locally
heavy rainfall...reducing visibility at times.

&&

Marine...
buoy data indicate that the current S swell remains sufficiently
high to maintain advisory level surf along S facing shores today...
with surf expected to decrease below advisory levels tonight. No
other significant S swells are expected through the weekend...with
a minor pulse of S swell expected from Monday through Wednesday. A
moderate northwest swell that peaked Wednesday will gradually subside
through Friday...just as a new moderate northwest swell begins to build.
This swell is expected to peak late Saturday and diminish into
Monday...just as another similarly-sized northwest swell begins to arrive.
Resultant surf is expected to remain below advisory levels along north
and west facing shores. After a bit of a hiatus...the Oahu surf
discussion /srdhfo/ was updated yesterday...and contains details
that can be loosely applied statewide.

Winds and seas will remain below Small Craft Advisory levels
through the forecast period.

&&

Hfo watches/warnings/advisories...
high surf advisory until 6 PM HST today for south facing shores of
all islands.

&&

$$

Discussion/marine...birchard
aviation...Foster

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