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Hawaiian Islands Synoptic Discussion and Guidance

029
FXHW60 PHFO 290630
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Sun May 28 2017

.SYNOPSIS...
Light winds with land and sea breezes will prevail through Memorial
Day as a weak pressure pattern lingers in the island vicinity. A few
windward showers will reach the area during night and morning under
the light easterly winds, with clouds and showers shifting to
leeward and interior areas in the afternoon. Trade winds will return
on Tuesday then becoming breezy toward next weekend. Typical trade
wind weather is expected for much of the week, with passing showers
affecting mainly windward and mountain areas.

&&

.DISCUSSION...
Surface troughs lingering in the state vicinity continue to keep
synoptic winds light to the area. Daytime convection is on the
decline as the evening progresses. There may still be some lingering
clouds along the eastern sections of the islands. An upper level
trough over the eastern end of the state that has brought some
atmospheric instability to the area continues to track northeast
this evening. This will allow the airmass in the island vicinity to
become more stable. As satellite imagery revealed not much low
clouds in the area, other than some windward showers, expect mainly
fair weather for the state through rest of the evening into early
Monday morning.

The aforementioned surface troughs are expected to persist in the
island vicinity for one more day. Thus, light winds will prevail
across the islands, with land breezes early in the morning, becoming
seas breezes in the afternoon. Clouds will develop over the islands
in the afternoon and evening and may bring some showers late in the
day. Rainfall amounts will be somewhat limited, due to a more stable
airmass return to the area. Sensible weather will be hot and humid
during the day.

High pressure will build north of the state Monday night and
Tuesday, and will bring trade winds back to the islands. Low clouds
and showers carried by the winds will affect mainly windward and
mountain areas. Trades are expected to firm up a bit by the later
part of next week as high pressure lifts northeast and strengthens.
Forecast solutions indicated a somewhat stable airmass will prevail
in the island vicinity, with minor changes in low level moisture.
Therefore, expect typical trade wind weather to return to state for
much of this week.

&&

.AVIATION...
A weak pressure pattern will remain in place through Monday, with
overnight land breezes and daytime sea breezes expected in most
areas. Showers will favor the coastal waters during the overnight
and early morning hours, and the interior of the islands during
afternoons and evenings. Some brief MVFR cigs/vsbys will be possible
in SHRA over the island interiors Monday afternoon/evening, but
predominantly VFR conditions are expected at the TAF sites through
06Z Tuesday.

No AIRMETs are currently in effect.

&&

.MARINE...
The higher than normal water levels experienced each day over the
weekend ended up breaking the April 29, 2017 record in Honolulu on
Friday and Saturday evenings due to a combination of sea level rise,
mesoscale features moving through the islands and King Tides. These
peak tides have begun to trend down and that trend is anticipated to
continue through the week. Coastal flooding impacts that have been
experienced around these late afternoon/early evening high tide
times over the weekend at the beaches, marinas and low-lying coastal
areas will likely persist through Tuesday before conditions trend
back to normal through midweek. Peak daily high tides are forecast
to even dip below average (1.9 ft above MLLW) Thursday through the
weekend.

The large south swell that peaked Saturday and led to advisory-level
surf along south facing shores will continue to ease into Tuesday.
The offshore buoys south of the islands reflect this trend and show
the bulk of the energy focused within the 14-15 second bands. For
Memorial Day, expect the largest surf through the morning hours with
light offshore winds. Onshore winds are expected to fill in by noon
and continue through the afternoon period as the surf fades. A
series of small background southerly pulses moving through will keep
the surf along south facing shores from becoming flat each day
through the upcoming weekend. For the long range, the latest models
are not supporting anything significant setting up within Hawaii's
swell window near New Zealand through the first week of June.

An out of season small to moderate north-northwest (330 deg) swell
associated with a gale that developed near the Date Line over the
weekend and tracked east to around 1400 nm north of the state is
forecast to fill in Monday night across the local waters. This
source should peak through the day Tuesday well below advisory
levels, then trend down into the second half of the week.

Light winds with land-sea breeze conditions prevailing near the
coasts will continue into Tuesday morning due to a weak surface
trough located just east of the Big Island and northwest of Kauai.
Trade winds will gradually return Tuesday through midweek as high
pressure builds north of the area. Small craft advisory conditions
will likely result due to strong winds beginning Tuesday night and
persisting through the rest of the week. These stronger winds are
expected to setup over the channels, Maalaea Bay and south of the
Big Island. As a result, rough and choppy surf along east facing
shores is expected through the second half of the week into the
upcoming weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

Aviation...Jelsema
Marine...Gibbs
Rest...Hui

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

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