Area forecast discussion...updated
National Weather Service Honolulu HI
645 am HST Thursday may 23 2013
Synopsis...
a pair of surface troughs to the north will keep winds light today.
That will allow sea breezes to produce clouds and showers over
interior areas this afternoon. Trade winds will spread over the area
tonight as a surface ridge builds north of the area. Trade winds
will persist through the coming week. The trades will bring showers
to mainly windward areas. A trough aloft may make these showers
fairly active.
&&
Discussion...
an upper level trough is being observed on WV satellite data...located
some 750 miles NE of the main Hawaiian islands. Surface analyses show
two decaying troughs...one just north of The Big Island and the other
lingering around 400 miles north of Kauai. Meanwhile...a broad surface high
remains centered far to the NE of the main Hawaiian islands.
The surface troughs will continue to break down today and allow for an
onset of returning trade winds across the islands...but not quick
enough in order to override sea breeze circulations this afternoon.
Therefore...there should be one more round of convection today
with showers favoring interior and mountain areas as sea breezes
push inland.
The influence of the upper level trough is still keeping tight
gradients at the middle/upper levels...with strong winds around 14-15
kft expected to continue today. Thus...the Wind Advisory for The
Big Island summits is now valid through 6 PM HST this evening...and
it may be extended if necessary.
The surface high NE of the islands will strengthen during the next
couple of days. This will bring a trade wind weather regime across
the Aloha state...starting tonight and becoming moderate to fresh
through the end of the week. Global models remain in fair agreement
with this overall scenario for the long term forecast...with
upstream moisture feeding windward and Mauka showers as the trades
establish.
&&
Aviation...
though trades are slowly returning...winds are light enough to bring
cloud buildups over interior sections of the islands. MVFR
conditions are possible this afternoon due to low ceilings and visible
in rain showers...as well as local MVFR visible in the vicinity of phto due to
vog. Otherwise...VFR conditions are expected at all terminals
today.
&&
Marine...
the current south swell will keep lowering...and surf along south
shores will remain below advisory levels for the next several days.
The northwest swell will gradually diminish through the weekend.
Trade winds will strengthen through the week...and are expected to
reach Small Craft Advisory levels over the windier locations near
Maui County and The Big Island by Friday night.
&&
Hfo watches/warnings/advisories...
Wind Advisory until 6 PM HST this evening for Big Island summits.
&&
$$
Donaldson
