Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 050711
Area Forecast Discussion
National Weather Service Honolulu HI
911 PM HST Sun Dec 4 2016
The inclement weather continues for the Hawaiian Islands this
week. The western half of the island chain will have a brief
break in the unsettled weather Monday and Tuesday before another
round of weather moves in for the second half of the new work
week. The eastern part of the chain will continue under relatively
cloudy skies and a high threat of showers throughout the week.
Dense, thick, multilayered stratiform clouds blanketed the island
skies today as they streamed in from the south ahead of an upper
level short wave trough. This trough is noted just to the west of
Kauai this hour. It is expected to move northeastward during the
overnight hours. With this motion, it will not totally clear Maui
and the Big Island of all the clouds. The instability will also
remain highest across Maui and the Big Island on Monday and
perhaps beyond that point.
Beneath the upper level trough, is a surface trough that will be
moving eastward. As it does so, the current southerly winds will
shift to the north and northeast across Kauai after midnight. The
trough is expect to dissipate over Oahu Monday with with models
agreeing in light trades winds filling in over the rest of the
island chain by Monday evening. Light trades lingers through
Tuesday, then turns slightly southeast Wednesday across the
smaller islands due to a surface trough just west of Kauai.
With this in mind. the light winds means local sea breezes
Monday and Tuesday. And with a tid bit more sunshine under an
unstable air mass, this may lead to some scattered convective
showers both tomorrow and Tuesday afternoons which includes Oahu
as well but more so across Maui County and the Big Island.
Therefore, the Winter Storm Warning and the Flash Flood Watch
that is set to expire at 6 am HST Monday, will likely be extended
for those islands, Maui and the Big Island, through at least Monday.
Depth of low level moisture increases across Kauai from 6k feet to
10k feet by Tuesday afternoon meaning a better chance for
afternoon showers for kauai.
As of 8 pm, weather radar shows Kauai just about in the clear
rain-wise while another batch of mostly light rain is cutting
through Oahu. The rest of the island chain remains under mostly
Instability and the inclement weather returns across Oahu and
Kauai County as early as Tuesday night while the GFS depicts a
surface trough stalling over Kauai Wednesday with southerly winds
across Oahu and Molokai. The surface trough fills by Friday but
the inclement weather remains as another upper level trough
dampens out over the islands and yet a new upper trough digs west
of the islands.
In essence, the islands are not out of the woods this week. More
An upper level trough over the island chain will keep conditions
unsettled from Oahu to the Big Island overnight, with some
improvement expected over Oahu after midnight. The upper trough
will weaken over the eastern islands on Monday, with conditions
slowly improving from west to east. Some brief MFVR cigs/vsbys
will be possible in SHRA as the area of disturbed weather moves
through, but predominantly VFR conditions are expected in most
AIRMET Sierra is in effect for mountain obscuration from Oahu
eastward to the Big Island. Conditions may improve over Oahu later
tonight, but should continue across Maui County and the Big Island
through the night.
AIRMET Tango is in effect for moderate upper level turbulence
between FL240 and FL400 across all islands. These conditions are
expected to continue through the night.
AIRMET Zulu is in effect for icing east of Kauai. Some improvement
is possible over Oahu later tonight. Elsewhere conditions are
expected to remain in place through the overnight hours.
The nearshore buoys across the windward waters has shown a decline
to less than 8 feet sig wave height except for the Hanalei buoy
which maintain a height of 10.5 feet this hour, which is slightly
above threshold for Small Craft Advisory /SCA/ of 10 feet. It is
likely elevated by a north-northwest swell of 7 feet which is a
foot higher than what Wave Watch is indicating. We will closely
monitor the readings but the SCA for waters around Kauai and
Oahu`s windward waters including the Kaiwi Channel, remains in
effect through the overnight hours. This swell of 7 feet 12 secs
translate to max surf of 13 feet, just below the High Surf
Advisory criteria of 15 feet.
No large swells are expected so surf is expected to remain below
High Surf Advisory levels over the coming week.
Flash Flood Watch until 6 AM HST Monday for Oahu Molokai Lanai
Kahoolawe Maui Big Island.
Winter Storm Warning until 6 AM HST Monday for Big Island
Small Craft Advisory until 6 AM HST Monday for waters around Kauai
and windward waters of Oahu including the Kaiwi Channel.