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Temp2.8 C
RH7 %
WindNE 0 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 130150

Area Forecast Discussion
National Weather Service Honolulu HI
350 PM HST Mon Nov 12 2018

A ridge north of the islands will maintain moderate to locally
breezy trade winds with a few brief showers over mainly windward
and coastal areas through Tuesday. Heading into midweek, winds
will weaken as the ridge is disrupted, which will allow for
afternoon clouds and showers over the interior of the islands.
Trades are expected to return for the second half of the week,
with increasing trade wind showers. Periods of high clouds are
expected beginning Tuesday, which could become thicker later in
the week.


Have made some tweaks to the forecast mainly in the first 36
hours, but no significant change to the forecast at this time.
High pressure north of the islands has brought some moderate to
locally breezy trade winds to the area, and these are expected to
continue through tomorrow, with winds beginning to weaken later
tomorrow as the ridge lifts north and weakens.

Dewpoints remain in the 60s across the state, with some low 60s
still being observed, keeping it feeling just a little cooler.
Expecting dewpoints to climb a few degrees over the next day or
so, with them rebounding to near 70 Wednesday in many locations.
This is around the time the winds will be weak enough to produce
some land and sea breezes. High clouds to the northwest of Kauai
this afternoon are on track to begin moving over the islands
tonight or tomorrow, and then thickening up overhead as we head
into midweek. While the light winds usually lead to afternoon
clouds and showers over the interior of the islands, and that is
what we have in the forecast, the amount of high clouds overhead
could inhibit some of this activity.

An increase in winds is expected Thursday and Friday as a boundary
approaches the state from the northwest. An upper level trough
developing to the northwest of the state will bring in colder
temperatures aloft, while moisture to the northeast is carried in
on the easterly flow. While differences in timing and placement
remain in the latest runs of the GFS and ECMWF, the models do
agree with instability moving over the islands Friday through
Sunday. That being said, with the colder air coming in from the
northwest and the moisture coming in from the east, at this time
it is difficult to pinpoint what, and where, things may develop.
While thunder cannot be ruled out at this time, without more
agreement in the models, will hold off putting the chance into the


Typical trade pattern expected tonight with flow generally
east northeasterly. Low stratocumulus clouds will push up against
the windward side of the mountain slopes, producing MVFR
conditions at times and periodic mountain obscuration. Moderate
east northeast winds may generate light to occasionally moderate
turbulence over and leeward of the island mountain ranges.
Otherwise, VFR conditions persist.

Airmet Tango in effect below 7000 feet for over and southwest of
local mountain ranges for moderate turbulence, lasting through
this evening. Winds and turbulence should ease slightly tonight.


High pressure centered north of the islands will be moving
eastward and will cause the northeast trades to veer more easterly
through Tuesday. Wind speeds are currently holding at the fresh
to locally strong range and is expected to continue through
tonight and possibly into Tuesday. Latest ASCAT pass showed winds
have decreased over the the Kaiwi Channel, thus the Small Craft
Advisory (SCA) has been adjusted to the typical windy areas
around Maui County and the Big Island through tonight.

A front passing north of the islands will bring a decrease of
trades Tuesday night through Wednesday night. Behind it, high
pressure will be building in from the northwest Thursday, and
fresh to locally strong northeast trades will be returning Friday
into the weekend.

The current north swell will continue to gradually subside
through Tuesday. A larger north-northwest swell with a peak around
7 foot swell height and a 14 second period, is expected to fill in
throughout the day Tuesday and peak Tuesday night into Wednesday.
Surf will likely reach advisory levels for exposed north and west
facing shores, potentially as early as Tuesday. Then, a reinforcing
northwest swell will arrive Thursday night into Friday with
heights near the advisory levels across north and west facing
shores. Another reinforcing north-northwest swell is possible
Saturday. The south facing shores will continue to feel a small
background southerly swell during the forecast period.


Small Craft Advisory until 6 AM HST Tuesday 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