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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 260631
Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST SUN SEP 25 2016
Trade winds will strengthen into Monday and will be locally breezy
through the upcoming week. Increasing moisture in the trade wind flow
will fuel an increase in windward showers tonight and Monday, with a
few showers spreading to leeward portions of the smaller islands.
After this moisture diminishes, a typical trade wind weather pattern
is expected from Monday night through Friday, with clouds and brief
showers favoring windward slopes, mainly during nights and mornings.
An increase in showers is possible next weekend.
Although afternoon soundings indicated that the island atmosphere is
quite stable, with a strong low-level subsidence inversion based
around 5 to 7 kft, an increase in trade wind showers is expected
overnight through Monday. After this moisture moves W of the islands
by Monday night, a fairly typical trade wind weather pattern is
expected through the week, with moderate to breezy trade winds
delivering passing clouds and showers that will be most active
during nights and mornings. An increase in moisture is possible next
weekend, as moisture associated with a disturbance about 1200 miles
ESE of the Big Island moves closer to the islands.
Trade wind speeds are expected to increase a little more through
Monday as a front lying between the islands and the trade-wind-
supporting high to the N will dissipate, allowing the pressure
gradient to increase over the area. As this high tracks E over the
next several days, it will continue to support locally breezy trade
winds over the islands. These stronger trade winds will help to
spread a few of the incoming showers to leeward areas tonight and
Monday. Otherwise, a fairly typical pattern of mainly windward and
mauka showers will prevail from Monday night through at least
Friday. An increase in moisture from the SE may combine with a weak
low aloft to the NW to bring an increase in showers next weekend.
Trade winds continue to bring low clouds with embedded showers to
the islands at times this evening. Much of the low clouds and
showers will affect mainly windward and mountain areas, providing
MVFR ceilings at times through early Monday morning. Winds may be
just strong enough to carry some low clouds and showers to the lee
areas of the smaller islands, spreading possible brief MVFR ceilings
to those areas as well. Otherwise mostly VFR conditions are expected
Kauai radar wind profile indicated rather robust winds at the lowest
levels this evening. Therefore, believe the winds have strengthened
enough to warrant an AIRMET for low level mechanical turbulence
immediately over and downwind of the mountains. The moderate to
locally brisk winds are expected to prevail at least through Monday.
A Small Craft Advisory (SCA) remains in effect for the typically
windy marine zones around the Big Island and Maui through Wednesday
and will likely need to be extended through the week.
Surf will be small, especially by Hawaii standards, through the
week. A series of mainly small pulses of southern hemisphere swell
will continue to bring small surf to S facing shores. A pair of
small, short-period NW and N swells will continue into Tuesday,
but resulting surf along N and W facing shores will be small.
Increasing trade winds will drive moderate short-period surf along
E facing shores this week.
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office