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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 210152

Area Forecast Discussion
National Weather Service Honolulu HI
352 PM HST Mon May 20 2019

Gentle to moderate east southeast winds expected through Friday which
will allow daytime sea breezes and nighttime land breezes to set
up over the islands. Clouds and showers will build each day across
island interior sections and then clear at night. Expect warm and
humid conditions to continue as well. Trade winds are forecast to
return over the Memorial Day weekend.


A 1027 mb surface high is positioned about 1200 miles northeast
of Kauai while an approaching front is about 800 miles northwest
of of Kauai. The two features will bring gentle to moderate east
southeast wind flow across the state over the next few days.
Because the wind direction will line up parallel to the island
chain, most areas will be blocked from the wind flow allowing land
breezes to set up tonight with cloud cover and showers decreasing
over the islands. Sea breezes will bring interior clouds and
showers around midday Tuesday. Exceptions to this will be along
the Maui windward and Hamakua coastlines which are generally more
exposed to east southeast winds. Both Hilo and Hana may see
stronger than typical wind speeds from the topographical effects.

The diurnal weather pattern will persist over through much of the
work week with mostly sunny mornings, cloudy afternoons and
clearing at night. Conditions will feel warmer and more humid
under this light wind regime. Rain amounts should be on the light
side, but can't rule out some moderate intensity showers
developing over the island interior sections each afternoon.

An upper level trough will gradually shift closer to the islands
to the west over the next several days, but should not destabilize
our weather. The front is expected to stall just west of Kauai
Tuesday night and then gradually shift away to northwest during
the middle and ending of the work week. Long range guidance shows
trade winds slowly building in over the Memorial Day weekend as
the front weakens and dissipates.


A ridge of high pressure N of Kauai will move S ahead of an
approaching front well NW of Kauai, weakening the trade winds and
causing them to veer to the SE over the smaller islands.

Shower activity will remain quite light across the islands through
Tuesday. A few cirrus clouds continue to stream across the state
today as well, ahead of a front far NW of Kauai. With the trades
weakening, expect some cloud build-ups and possible a light shower
or two over leeward areas of each island in the afternoons with
the development of a sea breeze. Otherwise, any showers will be
focused over inland and mountain areas. The coverage of the
clouds and showers is not expected to be extensive to warrant
AIRMET Sierra for mountain obscuration over the next 24 hours, so
VFR conditions will prevail.


Little change to the forecast this afternoon. High pressure to the
northeast will be moved to the east as a low moves north of the
islands over the next 24 hours or so. Winds will ease and turn to
the east to southeast as the low and its associated cold front
will remain north of the islands. The low will move to the north
as we head into the middle of the week, stalling the front to the
north of the islands. This will allow the surface ridge to build
back over the area during the second half of the week, allowing
for some strengthening of the winds as they become more

Surf is expected to remain below advisory levels through the week
for all shores. A series of small southwest and south swells will
produce small to moderate surf along south facing shores through
the middle of the week. The Memorial Day weekend could see
advisory level surf with the arrival of a larger long-period
south-southwest swell.

Small to moderate sized swells will impact the north and west
facing shores into the holiday weekend. Surf along east facing
shores will remain small through the middle of the week. As winds
increase during the second half of the week, we can expect a boost
to surf along east facing shores this weekend.

See the latest Oahu Surf Discussion (SRDHFO) for additional
details on surf and swell.





MARINE...M Ballard

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

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It was last modified on: Wed, Dec 17 2014 - 1841 UTC
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