Area forecast discussion
National Weather Service Honolulu HI
1000 am HST sun may 19 2013
Synopsis...
a surface trough will produce light winds and a chance of locally
heavy showers from Oahu to The Big Island today. A weak front will
bring north winds and some clouds and showers to Kauai today...and
to Oahu tonight. The trough will gradually weaken as it lingers near
the islands through mid-week. As high pressure builds northeast of
the area...trade winds will spread back over the islands by next
weekend. High surf will continue along the south shores into Monday
and will remain elevated through mid-week.
&&
Discussion...
a complicated weather pattern persists over the central North
Pacific. Water vapor imagery a shows low aloft north of the islands.
A nearly stationary surface trough extends from north northeast to
south southwest over Maui. A weak cold front just north of Kauai is
moving south at 10 to 15 miles per hour.
Clouds are isolated over most areas from Kauai to Lanai this morning
except for broken clouds and isolated showers over the North Shore
of Kauai. Clouds have increased rapidly over the slopes of Maui and
The Big Island since this morning and most areas are now cloudy.
There are scattered moderate showers over water north and south of
Maui County and overcast clouds and numerous showers just southeast
of The Big Island. The showers east of Maui are moving from the
south while showers near Kauai are moving from the north. The
atmosphere over the island remains unstable because of the low
aloft. Balloon soundings from 200 am showed weak temperature
inversions at 10000 feet at Lihue and 14000 feet at Hilo...with
precipitable water values of 1.16 inches at Lihue and 1.53 inches at
Hilo.
The trough near Maui will allow sea breezes to form over the
islands from The Big Island to Oahu later today...and there will be
enough instability for locally heavy showers on those islands.
There will be a slight chance of thunderstorms on The Big Island.
The weather on Kauai will be different. The weak front will move
over Kauai...bringing some clouds and showers but the cool
northerly flow behind the front will make the atmosphere more stable
and prevent the showers from becoming heavy. The weakening front
will bring clouds and showers to Oahu tonight before dissipating
near Molokai Monday morning.
The surface trough will linger near the islands through middle-week
allowing daytime sea breezes and nighttime land breezes to prevail.
This pattern will produce mostly cloudy afternoons and evenings with
showers concentrated over interior areas and partly clearing during
the overnight hours.
Models remain in good agreement showing the trade winds becoming
well-established by Friday. The convective pattern will end and the
trades will bring showers to windward and Mauka areas.
&&
Aviation...
the light winds will allow widespread sea breezes to develop from
The Big Island to Oahu this afternoon...with clouds and +shra over
interior and leeward areas leading to areas of MVFR vis/cig. Isolate
IFR conditions are also possible in areas of +shra...and in isolate
+tsra over Big Island slopes this afternoon. A weak cold front will
bring tempo MVFR conditions to the north side of Kauai.
&&
Marine...
winds and seas are expected to remain below Small Craft Advisory
levels statewide this week. A series of swells will keep elevated
surf along south facing shores through most of the week. Surf is
expected to remain above the advisory threshold through at least
early Monday morning. A marine weather statement remains posted for
waves breaking near channel entrances and possible Harbor surges.
&&
Hfo watches/warnings/advisories...
high surf advisory until 6 am HST Monday for south facing shores
of all islands.
&&
$$
Donaldson
