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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 251945
Area Forecast Discussion
National Weather Service Honolulu HI
945 AM HST Tue Oct 25 2016
High pressure north of the state will maintain moderate trade
winds through Wednesday. The trades will strengthen Wednesday
night and Thursday, then remain strong through the weekend.
Showers will favor windward and mountain areas, with an increase
in showers expected late this week and into the weekend, as the
trade winds strengthen and a weak upper level trough develops over
High pressure far to the north is propelling island trade winds at
moderate speeds with breezy conditions over the windier areas. Dry
conditions prevail over most areas this morning with only a few
weak showers over the windward areas from Oahu to the Big Island,
while windward Kauai has a few extra clouds and showers due to a
weak frontal remnant cloud band.
The high pressure will maintain moderate trade winds through
midweek with limited showers focusing over windward and mountain
areas with passing leeward showers over the smaller islands. Showers
will increase Wednesday and Wednesday night due to another frontal
band passing from northeast to southwest through the island
chain. The leeward Big Island will continue to see a diurnal
pattern of increasing afternoon clouds with scattered showers
forming over the slopes.
Trade winds will ramp up for the second half of the week as the
high pressure to the north strengthens and sinks south. Expect a
jump in wind speeds between Wednesday and Thursday with breezy
conditions and strong gusts. Strong trades will continue through
the weekend as the high remains in place.
Upper level ridging will keep a cap on showers through Friday
afternoon with light to moderate rainfall amounts expected within
trade showers. An upper level trough is expected to push the ridge
south of the state Friday night and bring cooler temperatures
aloft over the islands. The cooler temps will increase instability
and allow for increased shower coverage and intensity Friday night
and into the weekend. With the strong trades and increasing cloud
growth, expect a wet trade wind regime over the weekend and into
High pressure to the northwest of the Hawaiian Islands will
continue to drive northeasterly trade winds through the TAF
period. This will allow for mostly VFR conditions to prevail with
occasional isolated MVFR showers in windward and mountain areas.
No AIRMETs are expected over the next 24 hours.
Moderate trade winds with locally breezy conditions will remain
through Wednesday before the trade winds ramp up once again. The
typically windier waters around the Big Island and Maui County
will see Small Craft Advisory conditions through this time before
spreading across all waters, likely by Thursday. A High Surf
Advisory for the east facing shores may become a possibility
Friday into the weekend.
A long period northwest swell will peak tonight, before easing
over the next few days. Current observations at the Waimea (51201)
buoy are coming in about a foot higher than the Wave Watch model,
but surf should stay below advisory conditions. Models are also
suggesting a small bump in surf from the north-northeast direction
Wednesday night into Thursday. Another small northwest swell
should peak Saturday, with surf well below advisory levels. For
the south facing shores a small long period swell will bump surf
up slightly Wednesday into Friday.
Small Craft Advisory until 6 PM HST this evening 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