Current Conditions
Temp7.2 C
RH19 %
WindNNW 9 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 251344

Area Forecast Discussion
National Weather Service Honolulu HI
344 AM HST Sun Sep 25 2022

Light large scale southeast winds will become more easterly today
as the subtropical ridge flattens out ahead of a stalling cold
front far to the north of the Hawaiian Islands. Lighter large
scale winds will continue into Tuesday with sea breezes developing
from late morning to afternoon over all islands. Converging sea
breeze winds will allow a few showers to develop over mountains
and island interior sections by late afternoon to early evening.
More stable down sloping land breezes will clear out most of the
cloud cover over the islands. Trade winds will slowly strengthen
from Tuesday afternoon onward with a return to windward and
mountain cloud and shower activity from Wednesday onward, mainly
in the overnight to early morning hours.


The local radar imagery this morning shows rain falling along the
northwest coast of the Big Island. Periods of moderate to locally
heavy rain have fallen in this area, from leeward Kohala to
Waikoloa Village to Kona, through the morning hours. These showers
are produced by eddies just west of the Big Island, and in
southeasterly wind flow these coastal showers can cause stronger
than normal onshore winds to converge with the typical down slope
mountain breezes.

Light southeast winds will shift to a more easterly direction
today as an approaching cold front far north of the Hawaiian
Islands flattens out the subtropical ridge just north of the
state. Lighter large scale winds will continue to allow sea
breezes to strengthen through the afternoon hours with clouds
building over mountain and island interior sections. Increasing
stability aloft with a lowering trade wind subsidence inversion
will limit afternoon to early evening shower coverage into the
first half of next week.

The cold front will weaken and stall north of the islands by
Tuesday. Trade winds will strengthen from Tuesday afternoon onward
and become moderate to locally breezy range by Thursday as this
frontal trough erodes. The weather pattern will then shift back
to windward and mountain areas with passing showers developing in
the overnight to early morning hours from Wednesday night onward.


A weak southeasterly flow will persist today across
the state and allow for land breezes early this morning. By late
morning and into the afternoon, sea breezes will likely develop,
especially along the more sheltered leeward locations. Thus,
scattered shower activity will be most concentrated over the
interiors and elevated terrain. Isolated areas of MVFR ceilings
and visibility may accompany these showers, though not expecting
anything widespread.

There currently no AIRMETS in effect.


An area of low pressure remains far west of the state. Meanwhile,
a weak ridge of high pressure is located just north of Hawaii.
Expect light to moderate east to southeast winds to continue
today. As the low tracks further west tonight, winds will back to
more of an easterly direction and we should see light to moderate
trade winds through the first half of the week. Wind speeds may
approach Small Craft Advisory thresholds during the second half of
the week.

South swell will remain elevated through today, then decrease
through Tuesday, leaving only background south swell by the
middle of the week. Minimal energy is expected from the south
during the second half of the week. A small north-northwest swell
is forecast to arrive around Wednesday followed by a slightly
bigger pulse over the weekend. Light trade winds will keep small
surf in the forecast along east facing shores through at least
Wednesday with a slight increase expected towards the end of the
week as the trades strengthen.






Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office