Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
1000 am HST Tuesday Mar 31 2015
a low level trough near Kauai is expected to dissipate over the
Western Islands today and this evening. This will allow locally
strong trades to return to all areas Wednesday. Trade wind
conditions will persist into the weekend with showers favoring the
windward and mountain areas.
wind sensors on Kauai shows a predominantly light southerly wind
flow at or near the surface. This means a low level trough is
nearby... perhaps just west of Kauai. The GFS shows the trough...and
has an overall better assessment than the European model (ecmwf) /ec/. The GFS points
to the trough moving over Kauai this afternoon before dissipating
over Oahu this evening. In essence...there will be light and
variable winds over the area west of Molokai this afternoon and
The low level trough is being aided by any upper level shortwave
trough currently passing north of Kauai. This disturbance is setting
off isolated thunderstorms over the offshore waters north and
northeast of Kauai...and had triggered some locally heavy showers
earlier this morning on Kauai and Oahu.
We are not expecting thunderstorms this afternoon as most of the
instability from the upper trough remains north of the islands.
Moisture availability is limited at 1.25 inches precipitation waters... and
reaches no higher than 15k feet. However... the low level trough and
island heating will bring increased shower activity this afternoon
especially for Kauai and Oahu.
Elsewhere...winds from Molokai eastward will remain under light to
moderate east to southeast winds through tonight. As the low level
trough dissipates ... will spread westward reaching Kauai by
sunrise Wednesday. Additionally trades will strengthen to locally
strong over the waters around Maui and south of The Big Island
The trade wind regime is expected to continue into the weekend with
showers favoring the windward and mountain areas...especially nights
and mornings. However...there is some discrepancy between the ec and
GFS Thursday night through Saturday with the GFS bringing lighter
winds overall and increased moisture to The Big Island. We are
currently riding the ec solution and climatology with continued
moderate trades into the weekend.
no airmets currently in effect. But an airmet for mountain obscuration is
likely for Kauai and Oahu this afternoon and early evening as ample
moisture...light winds...daytime heating...aided by a trough results
in a showery afternoon for especially these two islands.
winds will remain below Small Craft Advisory /sca/ speeds through
tonight. Trades are expected to return to Kauai and Oahu by daybreak
Wednesday as the trough near Kauai and Oahu dissipates this evening.
The trades will continue to strengthen into Wednesday reaching
locally strong speeds by the afternoon...and a Small Craft Advisory...for waters
around Maui and south of The Big Island.
The current small northwest swell will dissipate by Wednesday. A
small south-southeast swell will also be on a gradual decline over
the next couple of days...followed by a small south-southwest swell
for the second half of the work week.