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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 070701
Area Forecast Discussion
National Weather Service Honolulu HI
901 PM HST Fri Dec 6 2019
An upper trough will move east of the area tonight with a drier
weather pattern filling in. Winds will be light over the weekend
as high pressure moves off to a position far northeast of the
area. A weak front will stall near Kauai early next week and high
pressure will pass by far north of the area. Light to moderate
trades can be expected early next week. Another front will
approach the area around Thursday with increased shower activity.
Have made some made changes to decrease sky coverage through
tomorrow morning. Satellite shows fewer clouds than the originally
forecast. Lighter winds will likely lead to clouds forming over
the interior or the islands tomorrow afternoon with a few showers.
Otherwise the remainder of the forecast remains the same. The
shortwave upper level system has moved to the southeast of the Big
Island, with some high clouds still over the coastal waters
southeast of the Big Island. A more stable and drier airmass is
moving over the region due to high pressure far to the northeast.
The southern end of a weakening front will approach Kauai Sunday
night and Monday, which will bring an uptick in showers mostly to
the Garden Isle. High pressure passing to the north will maintain
a trade wind flow, so expect some lingering moisture from the
front to ride in on the trades early next week. As the high moves
to the northeast, look for winds to weaken again Tuesday and
The models continue to show a stronger front approaching the
islands Thursday and Friday. Some model differences remain, but
expect increased shower activity with the front, and strong
northerly winds for a brief time behind the front, before trades
build back in.
The weather pattern is back to a northeast tradewind pattern.
Expect a few overnight showers, predominantly on the windward
slopes with passing MVFR conditions in these areas. Winds are
expected to be significantly lighter Saturday so a daytime sea
breeze-nighttime land breeze scenario should set up through
Saturday night. Since we are only expecting relatively brief MVFR
conditions on the windward slopes and the winds will be weaker, we
are not anticipating any AIRMETs through this forecast period.
Expect trade winds to diminish over the next 24 hours, and remain
light E-SE through the weekend, as an E-W oriented surface ridge
currently along 28N moves S over the island chain. The ridge will
drift N early next week as weak front stalls near Kauai. This will
result in light to moderate trade winds until mid-week, when a
stronger high building NW of the area brings strong NE winds
Wednesday into Thursday. Winds are expected to remain below Small
Craft Advisory (SCA) criteria until then, but combined seas may
get close to 10 feet in some zones this weekend as long-period N
and NNE swells arrive. Otherwise, seas will likely reach criteria
in many zones Tuesday and Wednesday as large NW swells arrive.
Overlapping long-period swells from the N and NNE are expected
through the weekend, and a High Surf Advisory (HSA) for E facing
shores will expand to N facing shores Saturday morning. Peak surf
heights along E facing shores may reach High Surf Warning criteria
(15 feet), and buoy observations will be monitored to determine
its necessity. The N/NE swell energy will diminish early next
week, but overlapping swells from the NNW/NW will likely bring
high surf to N and W facing shores for much of next week, with
warning level surf anticipated Wednesday/Thursday.
See the Oahu Surf Discussion (SRDHFO) for details on the sources
of the swells arriving in island waters.
High Surf Advisory until 6 PM HST Sunday for Kauai Windward-Oahu
Koolau-Olomana-Molokai Windward-Maui Windward West-Windward
Haleakala-Big Island North and East.
High Surf Advisory from 6 AM Saturday to 6 AM HST Sunday for
Oahu North Shore-Molokai Leeward-Maui Central Valley.
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office