Wind Advisory 37, NWS Honolulu, HI

791 
WWHW70 PHFO 290136
NPWHFO

URGENT - WEATHER MESSAGE
National Weather Service Honolulu HI
336 PM HST Thu Dec 28 2017

HIZ028-290245-
/O.CAN.PHFO.WI.Y.0037.000000T0000Z-171229T0200Z/
Big Island Summits-
336 PM HST Thu Dec 28 2017

...WIND ADVISORY IS CANCELLED...

The National Weather Service in Honolulu has cancelled the Wind
Advisory.

Winds have fallen below advisory levels and expected to continue
to decline tonight. Therefore, the Wind Advisory is cancelled.

$$

Foster

Area Forecast Discussion
National Weather Service Honolulu HI
823 PM HST Wed Dec 27 2017

.SYNOPSIS...
A weakening cold front is located just northwest of Kauai and
continues to move slowly to the southeast. Light northerly winds
are spreading over the western part of the state ahead of this
increasingly diffuse front. Only scattered showers are expected
ahead of and along the front. High pressure will build in behind
the front, bringing trade winds back to the region. A drier and
more stable airmass is expected to prevail along with the trade
winds through the weekend and into early next week.

&&

.DISCUSSION...
The front continues to creep southeastward toward Kauai this
evening. It is becoming difficult to discern on satellite imagery,
but our best guess is that the front is currently marked by a thin
rope cloud evident to the west of Niihau. Light northerly winds
are spreading into the western islands ahead of the front, while
stronger northeast winds lie behind it. Radar shows scattered
showers over/around Molokai and northeast of Oahu, with some
additional showers west of Kauai. Rainfall amounts at the gauges
during the past three hours ending at 7 PM have been very light,
with most locations remaining dry. Regional satellite imagery
depicts the main upper level support for the cold front lifting
away to the northeast of our area, with another weaker shortwave
moving across the western end of the state at this time. The 00Z
soundings show somewhat unstable conditions aloft with steep mid
level lapse rates and 500 mb temps ranging from -9C at Hilo
to -11C at Lihue, but moisture is lacking with PW values only
measured at 1.07 to 1.44 inches by the soundings, and very dry
conditions above 700 mb.

Winds on the Big Island summits continue to be somewhat elevated
this evening, but have been running slightly below wind advisory
levels. Model guidance suggests that winds may increase a bit more
overnight into Thursday morning, but then should drop off
significantly Thursday afternoon/evening. Will continue to
monitor for possible advisory issuance during the night.

Otherwise, expect just scattered showers at most overnight, as
there appears to be insufficient moisture available for the
passing shortwave to generate any thunderstorm activity ahead of
the front. The existing forecast appears to be on track.

The weakening front will likely wash out over Maui County on
Thursday, with northerly winds spreading over the state for a
brief time before trade winds build in Thursday night and Friday.
High pressure to the north of the state will then be the
controlling synoptic weather feature for our region through
the weekend and into next week, including New Years Day. Expect
moderate to fresh trade winds, along with a stable airmass. This
will produce typical trade wind weather for the most part, with
passing showers focused over windward and mauka areas. Remnants of
an old front embedded in the trades may bring slightly wetter
conditions to the state as they move through late Sunday into
Monday, otherwise the leeward areas should remain mostly dry.

&&

.AVIATION...
A weakening cold front will move through Oahu this evening with
only scattered light showers possible. Light wind speeds on
Thursday will allow nocturnal offshore land breezes and day time
onshore sea breezes to develop. On Thursday afternoon high
pressure will build in from the west. Kauai and Oahu will
transition back into north to northeasterly trade winds with trade
winds spreading down the rest of the island chain by Thursday
night. A typical trade wind weather pattern will set up for the
long term with periods of cloud ceilings and showers over mountain
areas and along the northeastern windward coasts.

No AIRMETs in effect. An AIRMET Tango may be needed this weekend
as surface wind speeds increase creating the potential for low
level mechanical turbulence down wind of mountain ranges.

&&

.MARINE...
Southwest winds ahead of a weakening cold front will shift out of
the north to northeast as the front moves slowly across the state
through early Thursday. Winds are expected to remain below the
Small Craft Advisory (SCA) criteria. An extended period of trade
winds is forecast from later this week into early next week.
Winds may reach the SCA criteria over the typically windy waters
adjacent to the islands of Maui County and the Big Island
starting Saturday night or early Sunday.

The current north swell continues to decline early this evening.
A reinforcing north swell is expected to build later tonight and
peak Thursday. Surf produced by this swell is expected to remain
below the High Surf Advisory threshold along north facing shores
from Oahu eastward. Note that this swell will likely be slightly
larger near the western end of the island chain. As a result,
elevated surf just below the High Surf Advisory threshold is
possible along north facing shores of Kauai and Niihau on
Thursday.

A moderate west-northwest swell is forecast during the upcoming
New Year Holiday weekend. However, surf is expected to remain
below the High Surf Advisory thresholds along north and west
facing shores. The next chance for large surf along north and
west facing shores appears to be around next Tuesday according to
the Wave Watch III model, which indicates a large northwest swell
may spread across the state.

South facing shores will continue to see a small bump in surf
through Saturday due to a couple of long-period south and
southwest swells. East facing shores will likely have increasing
rough surf from Friday through early next weekend due to the
strengthening trade winds.

See the latest Collaborative Nearshore Swell and Wind forecast
for Oahu for additional details on the sources of swells and surf.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

DISCUSSION...Jacobson
AVIATION...Bohlin
MARINE...Houston