Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 250630
Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST SAT SEP 24 2016
Light to moderate trade winds will gradually strengthen on Sunday
and Monday as high pressure builds far north of the state. A typical
trade wind weather pattern is expected over the next week, with
clouds and brief showers favoring windward slopes and coasts, mainly
during nights and mornings. While most leeward areas will be dry,
leeward Big Island will see afternoon and evening clouds and a few
showers. However, a brief increase in shower activity is expected on
A stable trade wind pattern settled over the island chain today as
deeper moisture moved away to the SW, and a benign weather pattern
prevails this evening. This would be the cast statewide, but an
isolated pocket of heavy showers is noted on radar near the Big
Island`s Keahole Point. These are expected to diminish relatively
soon. Rainfall elsewhere has been meager, and this is expected to
persist overnight and Sunday, with mostly dry weather expected.
Trade winds will be gradually increasing on Sunday and Monday. At
the moment, the pressure gradient over the islands is somewhat
diminished, due to the presence of a cold front about 650 miles NW
of Kauai. The front will stall and begin to slowly dissipate on
Sunday, allowing strong high pressure passing to the N (near 40N) to
tighten the local pressure gradient. As a result, trade winds will
be on the rise on Sunday, and will become locally breezy on Monday.
An area of low-level moisture associated with a weak mid-level
trough is seen about 500 miles E of the islands this evening, and
model guidance has been consistent in indicating that it will arrive
on the trade wind flow late Sunday night through most of Monday.
This will lead to an increase in mainly windward showers, but
significant rainfall accumulations are not expected.
Locally breezy trade winds and a typical shower pattern focusing
clouds and showers over windward areas will prevail from Tuesday
through at least Friday. Heading toward next weekend, the GFS and
ECMWF are depicting an increase in moisture as the low-level flow
veers to the SE and a low aloft develops NW of the islands. Some
changes may be made to the extended forecast if the 00Z ECMWF
guidance concurs with the latest 00Z GFS.
Trade winds in the light to moderate range will continue into Sunday
then strengthen late Sunday. Expect windward sections of the islands
to see some MVFR ceilings at times as the trades bring low clouds
with embedded showers to the area. Lee areas of the Big Island may
also see brief MVFR ceilings as well, as convection will linger
through early part of the night. Otherwise, VFR conditions will
prevail for most areas.
No AIRMET is anticipated overnight.
Moderate to fresh trade winds will prevail through tonight
followed by an increase in winds Sunday and Monday as high pressure
builds to the N of the islands. A Small Craft Advisory (SCA) will
likely be posted for the typically windy waters around the Big
Island and Maui on Sunday, and the SCA will likely remain in place
through much of the week.
Surf will generally be on the small side through the next week. A
series of mainly small pulses of SSW swell will continue. A very
small, relatively short-period NW swell is already diminishing and
this swell will fade Sunday. A new relatively short-period NNW swell
is expected Monday and Tuesday, but once again will be small.
Increasing trade winds will lead to gradually increasing wind waves
that will drive moderate short-period surf along E facing shores.