Waianae, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

296
FXHW60 PHFO 150102
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
302 PM HST Thu Nov 14 2024

.SYNOPSIS...
Windy trade winds will persist into the weekend with bands of
showers being carried in on the trade wind flow. Showers will be
focused over windward and mauka areas, with some of the showers
being carried over to leeward areas. A slot of drier air moving in
this afternoon through Friday will bring critical fire weather
conditions to leeward portions of the state tomorrow. Additional
moisture coming in Saturday will boost shower activity once again.

&&

.DISCUSSION...

GOES-18 analyzes an 0.75" PWAT airmass on the doorstep of the island
chain this afternoon. This airmass coincides roughly with the region
of diminished cloud cover and/or low clouds that are stable in
appearance on the regional visible loop and will be ushered in on
strong trade winds tonight into Friday. Much drier conditions
anticipated tomorrow with very limited shower potential over the
western end of the state. Exceptions to the rule include windward
portions of Maui and the Big Island where upstream moisture will
continue to pile up on the windward slopes bringing persistent
clouds and rainfall there. Strong 1038mb high pressure maintained
by ridging aloft will support windy trades throughout this time.
The Wind Advisories for both the low elevations and the Big
Island Summits therefore remain in effect with no adjustments
needed.

A weakly convergent but well-organized band of trade wind showers is
noted on visible imagery about 250 miles N of the islands. This
band of showers exists along a subtle area of increased pressure
rises within sprawling surface high pressure and has been well-
advertised by the guidance. As mid-latitude troughing impinges on
resident mid-level ridging and causes it to deamplify and fold
eastward late Saturday into Sunday, this corridor of enhanced
moisture will be forced through the area Saturday afternoon
through Saturday night. This results in higher-than-fnormal
confidence in a brief period of wet trades this weekend.

Continued surface pressure falls across the central and northern
Pacific will cause trades to weaken during the first half of next
week. Drier conditions can be expected as 850mb flow veers to the
southeast, steering limited moisture parallel to the island
chain.


&&

.AVIATION...

Strong easterly trade winds will decrease slightly overnight then
rebuild tomorrow. Blustery trade winds will continue to deliver
showery low cloud clusters towards windward slopes and coasts.
Occasional spillover showers possible across leeward areas,
especially this evening. Occasional periods of MVFR CIGS/VIS
within passing showers.

AIRMET Sierra for mountain obscuration remains in effect for
north through east sections of Kauai, Oahu, and Windward Big
Island. Conditions may improve briefly this evening, but are
expected to redevlop overnight.

AIRMET Tango for moderate low-level turbulence over and downwind
of the mountains will remain posted until further notice. An
AIRMET for moderate upper level turbulence associated with quick-
moving trough aloft passing just north of the state has also been
issued, but will not likely remain in effect past midnight.

&&

.MARINE...

A strong high pressure system north of the Hawaiian Islands
will remain in place over the next few days. Strong and gusty
trade winds are expected to blow through Sunday, peaking on Friday
and Saturday then slowly decreasing from Sunday onward as a low
pressure system weakens the ridge north of the state. A Gale
Warning is in effect today through Saturday for the windier
waters and channels around Maui and the Big Island. The Small
Craft Advisory remains in effect for all remaining coastal waters
for the same time period.

The large, long-period northwest (320-330) swell will continue
trending down and shift to a more northerly direction (340-360)
through Friday. Surf heights will decrease further into the
weekend and get minor bumps from small reinforcing northwest
swells. Long range models show the potential for a larger north
(360) swell by the middle through the latter half of next week.

Rough and choppy surf along east facing shores will hold through
the weekend due to the strong trade winds. A High Surf Advisory
for exposed east facing shores is in effect through Saturday. Surf
heights should gradually decrease next week as trade wind speeds
decrease.

Surf heights along south facing shores remains small through the
period.

Peak monthly tides are forecast from Nov 15th to 18th. These high
tides will combine with elevated seas due to strong trades and
rising easterly seas, which may increase coastal inundation
impacts for vulnerable locations during early morning high tides.
A coastal flood statement is in effect for that time.


&&

.FIRE WEATHER...
In the wake of this morning`s band of showers, a dry airmass has
begun to push into the area. This airmass will bring dewpoints a
few degrees lower than those observed today and will result in
tomorrow afternoon`s RH values falling to around 45% or slightly
lower. Fuels remain dry and windy trades will continue throughout
this time. The Fire Weather Watch for Friday has therefore been
upgraded to a Red Flag Warning. Additionally, there is low
potential for critical fire weather conditions to continue into
early Saturday afternoon. A band of showers advancing toward the
island chain will then end fire weather concerns no later than
Saturday evening.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 10 AM to 6 PM HST Friday for Niihau-Kauai
South-Kauai Southwest-East Honolulu-Honolulu Metro-Ewa Plain-
Waianae Coast-Oahu North Shore-Waianae Mountains-Molokai West-
Molokai Leeward South-Lanai Windward-Lanai Leeward-Lanai South-
Lanai Mauka-Maui Leeward West-Maui Central Valley North-Maui
Central Valley South-South Maui/Upcountry-South Haleakala-Big
Island South-Big Island Southeast-Kohala-Big Island Interior.

High Surf Advisory until 6 AM HST Sunday for Olomana-Maui
Windward West-Kauai East-Koolau Windward-Molokai Southeast-
Windward Haleakala-Kipahulu-South Haleakala-Big Island Southeast-
Big Island East-Big Island North.

Wind Advisory until 6 AM HST Saturday for Lanai Mauka-Kahoolawe-
Maui Windward West-Maui Leeward West-Kohala-Big Island Interior-
Molokai North-Molokai West-Molokai Leeward South-Lanai Windward-
Lanai Leeward-Maui Central Valley North-Maui Central Valley
South-South Haleakala-Big Island South-Big Island Southeast-Big
Island North.

Wind Advisory until 6 AM HST Friday for Big Island Summits.

Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Big Island
Windward Waters.

Gale Warning until 6 AM HST Sunday for Maalaea Bay-Pailolo
Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters.


&&

$$


DISCUSSION...JVC