115 
FXHW60 PHFO 211354
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
354 AM HST Mon Nov 21 2022

.SYNOPSIS...
A strong high pressure system to the north will generate breezy 
to strong trade winds into Tuesday. Brief passing showers are 
expected mainly over windward and mountain areas through Wednesday.
A cold front will sweep from west to east down the island chain 
from Wednesday evening through Thanksgiving Day, delivering a 
period of showers for all islands, followed by another round of 
strong and gusty northeast winds that will ease by Friday night. 
Lighter winds are forecast from Sunday onward as the ridge north
of the region weakens.

&&

.DISCUSSION...
A strong high pressure system north of the state will produce 
breezy to strong trade winds across the region into Tuesday. An 
approaching cold front will weaken the ridge north of the state 
and decrease wind speeds to more moderate levels from Tuesday 
night through Wednesday. 

A wind advisory remains in effect until 6 PM HST this evening for
portions of Oahu including most areas in Maui and Hawaii 
Counties. Trade wind temperature inversion heights will lower
later today with decreasing shower activity lasting into Tuesday
night. Expect brief passing showers mainly over windward and 
mountain areas, favoring the overnight to early morning hours in
this pattern. One exception to this forecast will be more 
numerous showers over windward areas of East Maui and the windward
Big Island through Wednesday. Shower activity will then trend 
upwards across all islands by Wednesday afternoon as prefrontal 
convergence bands produce showers ahead of the approaching cold 
front.

A vigorous cold front will sweep from west to east across the
state from Wednesday night through Thursday. Expect a 6 hour or
less period of rainfall for all islands as the frontal cloud band
moves quickly through the region. A strong high pressure ridge 
will build in behind the front with another round of strong and 
gusty winds in the forecast from Thanksgiving Day into Friday. 
These strong northeast winds will likely exceed our wind advisory 
thresholds and create problems for outdoor holiday events. Please 
consider indoor party planning for this Thanksgiving as winds this
strong may blow away small items and tents. 

Winds are expected to ease from Friday into the weekend as a cut 
off low forms on the front northeast of the islands, and the high 
rapidly weakens. Light winds will develop from Sunday onward with
land and sea breezes forming over all islands. 

&&

.AVIATION...
Strong, gusty trades will continue through the forecast period and
will focus clouds and showers mainly over windward and mauka
areas. Shower intensity will tend to be limited over the western
end of the state due to increasing stability. However, pockets of
deeper moisture within the comparatively low stability environment
over the eastern end of the state will favor periods of heavier
showers over Windward Big Island and Maui. This will especially be
the case this evening when an expanding coverage of showers will
likely bring widespread MVFR to these areas.

AIRMET Tango for lee turbulence will remain in effect through the
forecast period.

AIRMET Sierra for mountain obscuration may be needed this evening.

&&

.MARINE...
A tight pressure gradient across Hawaii will result in strong to
gale force trade winds across the coastal waters through tonight.
A Gale Warning is in effect for Pailolo and Alenuihaha channel 
through this evening. A Small Craft Advisory (SCA) is also in 
effect for all Hawaiian waters through today, with the likelihood 
that at least some of the waters will be extended into beyond 
then. A slight weakening in the winds is forecast Tuesday through 
the day Wednesday as the driving high moves away. In its place, a 
vigorous cold front will impact the area beginning Wednesday night
and continuing through Friday, which will produce gale force 
winds and rough seas in combination with a large north northwest 
swell.

Currently, a long-period northwest swell (310 degrees) will fill 
in throughout the morning. A High Surf Advisory (HSA) is now in
effect through 6 am Tuesday as the offshore buoys have indicated 
the swell coming in slightly above guidance. The swell is expected
to decline Tuesday and Wednesday. A much larger north northwest 
swell will build overnight Wednesday night into Thanksgiving Day. 
The peak of this swell could reach warning levels and it could 
coincide with the spring high tide during the early morning hours 
Thursday. Adding the potential for gale force winds along the cold
front, there could be significant overwash issues and large wave 
run up along north facing shorelines both on the mornings of 
Thanksgiving and Friday. Latest wave run up forecast from PACIOOS 
is indicating wave run- up heights exceeding 8 feet and 
approaching 10 feet. Above 8 feet, overtopping of lower roadways 
closer to the shore should be expected. Areas exposed to north 
swells on other shorelines should see a significant rise in surf 
as the north northwest swell moves in. 

Surf along east facing shores will see a steady rise during the 
next few days as the trades strengthen. Other than some wind 
swell wrap, south facing shores will see minimal energy for the 
foreseeable future. 

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Tuesday for north and west
facing shores of Niihau, Kauai, Oahu and Molokai.

Red Flag Warning from 9 AM HST this morning to 6 PM HST this 
evening for all leeward areas. 

Wind Advisory until 6 PM HST this evening for portions of Oahu and
most areas of Maui and Hawaii Counties.

Small Craft Advisory until 6 PM HST this evening for all Hawaiian
coastal waters.

Gale Warning until 6 PM HST this evening for Pailolo Channel-
Alenuihaha Channel.

&&

$$

DISCUSSION...Bohlin
AVIATION...JVC
MARINE...Shigesato