Current Conditions
Temp9.3 C
RH30 %
WindNE 8 mph
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 091951

Area Forecast Discussion
National Weather Service Honolulu HI
951 AM HST Mon Dec 9 2019

A stalled front north of the state will maintain light easterly
winds through the first half of the week. Mostly dry and stable
weather will prevail with a few clouds and showers setting up
over interior areas each afternoon due to sea breezes. Increasing
moisture associated with a second front will bring increasing
showers Thursday and gusty northeast winds by Friday.


A stalled front just north of Kauai will weaken in place over the
next few days bringing benign weather and light easterly trade
winds to the islands through midweek. Sea breezes are expected
along leeward coastlines, and interior and mountain locations
will see afternoon clouds and limited light showers.

Stable conditions aloft are keeping cloud tops limited to around 8
thousand feet and any showers that do form over the islands have
been short-lived. A weak trough to our south has increased shower
activity over the coastal waters south of the Big Island, and a
low level convergence area has created a thin line of showers over
the Kauai Channel. Otherwise, skies over the islands this morning
are mostly clear. Expect increasing cloudiness this afternoon over
interior areas and over the mountains as daytime heating creates
some upward motion and leeward sea breezes kick in. Expect similar
conditions through Wednesday.

Thursday, synoptic weather conditions begin to change as a second,
more robust cold front approaches from the northwest, and an
upper level trough brings colder temperatures aloft that will
trigger increasing shower coverage and rainfall intensity. Showers
are expected to increase over Kauai Thursday evening and then the
rest of the state Thursday night. The front will also bring
strong gusty northeast winds Thursday night and Friday. However, the
GFS and ECMWF global models are having quite a hard time coming
into agreement with the details of the front and upper trough at
this time. Historically, similar weather patterns have brought
the lion's share of rain to Kauai, with the rest of the state
seeing frequent windward showers and passing leeward rainfall. The
forecast will continue to be updated as the model solutions

Saturday, the front is forecast to retreat to the north and
dissipate while the upper trough weakens and the atmosphere
becomes more stable. Trade winds are expected to drop to moderate
levels while shower coverage decreases and focus over windward and
mountain areas.


VFR conditions prevail at all the TAF sites and these conditions
are expected to prevail through the day on into the evening
hours. Elsewhere Vfr conditions prevail across the remainder of
the state. Some local MVFR conditions may occur during the
afternoon and evening hours over mountainous terrain as daytime
heating allows for some cloud buildups and isolated -shra.


There are no warnings or advisories in effect for the Hawaiian
coastal or offshore waters today. A ridge north of the area will
maintain light to moderate winds over the area through tomorrow
night. Winds will strengthen starting Wednesday as a front moves
over the area from the northwest and a strong high builds in
behind it.

A new northwest swell is beginning to fill in and will spread
down the island chain today. This swell is forecast to produce
surf above the advisory threshold along north and west facing
shores starting this evening and holding through Wednesday
morning. As this swell subsides Wednesday, a much larger northwest
swell is expected to produce surf well above warning levels along
north and west facing shores of the smaller islands beginning
Wednesday night into Friday. This swell may also be large enough
to produce advisory level surf along west facing shores of the Big
Island. The swell is expected to gradually subside through Friday






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