Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
830 PM HST Friday Apr 24 2015
a front approaching from the west is forecast to bring showery
weather to the smaller islands over the weekend. The front will
reach Kauai early Saturday evening...followed by Oahu early Sunday
morning. The front will then stall and dissipate over Maui County
between Sunday evening and Monday. A strong high following the front
will settle north of Kauai Monday and bring breezy trades through at
least Wednesday. The Big Island will be mostly dry through the
The front that is expected to affect the islands is 160 miles west
of Kauai/S Na Pali coast as of 7 PM HST. The front is inching its
way eastward at about 5 miles per hour. The European model (ecmwf) and GFS are in pretty good
agreement with the timing of the front...as noted in the synoptic
section. Despite the lack of upper level support...the front will
still be carrying a punch with the GFS showing moisture reaching up
to 18 thousand feet. This is good enough for some locally heavy
downpours which will be added to the 4 am forecast package. Sunday
appears to be shaping up to be a damp one for Kauai and Oahu.
A broad 1036 mb surface high is forecast to enter the picture Sunday
night when it moves into position north of Kauai and starts
supplying the islands with breezy trades that will last through at
least Wednesday. Monday will likely be both showery and breezy for
much of the windward areas with some showers blowing over to leeward
locations as well. Normal trade wind showers are on tap from Tuesday
on... although the trades will continue strong and gusty.
In the mean time...rather dry condition prevail across the main
Hawaiian islands this early Friday evening. Best threat for showers
overnight is Kauai where low level convergence could set off some
showers in the southerly flow. Satellite imagery shows a few showers
approaching windward Big Island and Hana area of Maui from the east.
So these places may receive a few drops overnight. Pretty much dry
but humid elsewhere.
VFR conditions will prevail across most areas overnight into
Saturday. Southerly flow ahead of a slowly approaching front may
produce some MVFR ceilings and showers across southeast/S coasts and slopes. No
airmets are in effect at this time...but airmet Sierra for mountain
obscuration could be needed later tonight or Saturday morning if low
clouds and showers become concentrated in a particular area.
The frontal band will move into Kauai early Saturday evening...
accompanied by clouds and showers with an increasing probability
of MVFR conditions.
surf along east and south facing shores will continue to subside
through the weekend. A larger north northwest swell is set to arrive
Sunday. It will build and shift from the north Monday night. This
swell will likely produce surf above the advisory threshold along
north facing shores by Monday morning...and could produce
advisory-level surf along east facing shores Tuesday as the swell
direction shifts out of the north northeast.
A Small Craft Advisory /sca/ remains in place for the windward Big
Island waters due to the southeast winds accelerating along the
Strong northeast winds will spread down the island chain from Kauai
to The Big Island from Sunday night through Monday night. A Small Craft Advisory is
likely for the waters surrounding the smaller islands including the
Small Craft Advisory until 600 PM Saturday for Big Island windward