Area forecast discussion...c0rrected
National Weather Service Honolulu HI
400 am HST Tuesday may 21 2013
Synopsis...
a land and sea breeze weather pattern will persist over the islands
through Wednesday as an area of low pressure stays several hundred
miles north of the state. Lingering moisture associated with the low
pressure will bring slightly higher chances of rain to the eastern
portion of the state today. Trade winds will rebuild over the
islands by Thursday as the area of low pressure drifts away and
dissipates while a surface high pressure moves to far northeast of
the state.
&&
Discussion...
an area of surface low pressure persists in the island vicinity
this morning...keeping winds light over the islands. Land breezes
have developed overnight resulting in decreasing showers over the
islands. Moisture from a dissipating front...as well as low level
convergence bands...lingers over the eastern portion of the main
Hawaiian islands. The moisture...coupled with a slightly unstable
air mass...as depicted by early morning Hilo sounding...has allowed
some deeper convection to develop in the Maui County and Big Island
vicinity since last night. There is also a batch of low clouds
affecting Kauai...though the early morning Lihue sounding indicates
the air mass is more stable and drier compared to Hilo/S. Strong
winds associated with an upper level low pressure system continue
to affect the summits of The Big Island early this morning. The
winds will probably last through this evening...therefore a Wind
Advisory remains in effect for that area. Expect a repeat of
yesterday/S weather over the islands today as the state/S weather is
still pretty much under the influence of the nearby low
pressure...with highest threat of rain and locally heavy showers
over the eastern islands. The rest of the islands may see a chance
of rain...especially during the afternoon and evening with
convective clouds under daytime heating.
The area of surface low pressure will slowly weaken and drift away
from the islands in the next couple of days...as the associated
upper level cut-off low lifts north. Winds will remain light enough
over the islands Wednesday such that the present convective weather
scenario will continue. Lingering moisture associated with low level
convergence and the old frontal boundary is also expected to hover
nearly the eastern islands while slowly dissipating. Therefore...a
slightly higher chance of rain is expected over Maui County and The
Big Island Wednesday.
Forecast charts indicate a surface high pressure will move to
far northeast of the state by Thursday. As the surface low pressure
system drifts away and dissipates...trade winds will slowly rebuild
over the islands. Moreover...the surface pressure gradient across
the islands is expected to tighten by the weekend. Trade winds will
strengthen and become locally breezy. Passing low clouds and showers
will affect mainly windward and Mauka areas...and may even reach the
Lee areas of the smaller islands at times. Forecast charts do hint
the development of a weak upper feature near the Western Islands
over the weekend. This feature may enhance the trade showers at
times.
&&
Aviation...
VFR conditions continue for all taf sites this morning...with low
clouds lingering in the island vicinity. There are some deeper
convection present in the surrounding coastal waters with tops to at
least 10k feet...bringing localized MVFR ceiling and rain showers. Expect
mostly VFR conditions to prevail for all the taf sites
today...though with moisture lingering over the state...especially
over the eastern islands...more brief MVFR ceiling and rain showers
conditions may develop during the afternoon and evening over the
islands.
&&
Marine...
the high surf advisory for south facing shores continues through
this evening as a large south swell persists. Elevated surf for
south facing shores will last at least through Wednesday. An out of
season... moderate...west-northwest swell is expected to arrive
tonight and peak Wednesday into Thursday...bringing near advisory
level surf for north and west facing shores.
Trade winds are expected to be strong enough by the weekend for
small craft wind conditions to develop over the windier Maui County
and Big Island coastal waters.
&&
Hfo watches/warnings/advisories...
high surf advisory until 600 PM HST this evening for south shores of
all islands.
Wind Advisory in effect for Big Island summits until 6 PM HST this
evening.
&&
$$
Hui
