318 
FXHW60 PHFO 101949
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
949 AM HST Wed Jan 10 2024

.SYNOPSIS...
Lingering moisture from a dissipated front will produce scattered
showers over portions of the Big Island and Maui through tonight,
while a cool and light westerly flow brings a few showers to
mainly north and west slopes elsewhere. A front will quickly move
down the island chain Thursday and Thursday night, bringing 
strong and gusty northwest winds, a period of rainfall, and rather
cool conditions. Mainly dry and pleasant conditions will prevail 
Friday night through Monday.

&&

.DISCUSSION...
The front that moved down the island chain during the last couple
of days has weakened, leaving a shallow pool of moisture over the
Big Island and Maui within a light westerly surface flow. Light 
showers are affecting mainly western slopes of the Big Island and,
to a lesser extent, on Maui this morning and will likely persist 
into tonight. These islands could also experience a few showers 
popping up on windward slopes this afternoon as sea breezes drive 
shallow convection. The parent low associated with the front is 
also producing a weak trough near Kauai. The post frontal westerly
flow is quite stable and somewhat dry, but the trough is managing
to trigger some light showers that are affecting northern slopes 
of Kauai this morning. Expect clouds and a few light showers to 
persist over this portion of Kauai, while some light rainfall 
makes its way to Oahu later today and tonight.

Another surface low will rapidly develop within 500 miles north 
of the state on Thursday, sending a fast moving front down the 
island chain that will bring strong and gusty winds on Thursday 
and Thursday night. Moisture along the front is not expected to be
deep, lowering flood concerns, but a strong jet streak driving 
the front will likely support a brief period of moderate to heavy 
showers as the quickly moves through. The jet streak and proximity
of the parent low will bring strong and gusty west to northwest 
winds just ahead of and behind the front. These winds will affect
Kauai around late morning, Oahu in the afternoon, and the rest of
the island chain Thursday night. We will be taking a closer look 
at the need for a Wind Advisory for the lower elevations, but 
confidence is high that very strong winds will impact the 
Haleakala summit and Big Island summits by Thursday afternoon.

A rather cold air mass, by Hawaii standards, will fill in behind
the front on Friday as some lingering shower activity affects
mainly northern slopes. Daytime high temps will only reach the mid
70s, and dew points in the moderate to breezy northerly winds 
will fall to around 50 deg F, providing a chill to the air. Strong
summit level winds will persist.

Dry conditions will prevail during the weekend. Northerly winds
will ease on Saturday and switch to light southerly on Sunday and
Monday as another front approaches the region.

&&

.AVIATION...
A weak and slow moving cold front is over Big Island and a 
surface trough over Kauai late this morning. Clouds and showers 
will linger today and tonight around the Big Island around the 
front, with more widely scattered showers around the western half 
of the state as the trough advances eastward eventually catching 
up to the cold front.

AIRMET Sierra is posted for tempo mountain obscuration across
leeward Big Island, with the possibility of other portions of the
Big Island being added back into the AIRMET later today. Brief
MVFR ceilings possible across Kauai today, and Oahu this afternoon
along the trough, while VFR conditions should prevail elsewhere.

Strong northwest winds and showers along another front will build
into Kauai by midday Thursday and quickly spread eastward down 
the island chain.

&&

.MARINE...
A weak cold front will continue to move southeast and dissipate 
east of the Big Island while gentle to moderate westerly winds 
persisting behind the front through early Thursday. Another cold 
front will move into the waters surrounding Kauai Thursday 
morning. This frontal band will swiftly move southeastward across 
the state reaching the Big Island by late Thursday night. Fresh to
strong northerly winds will fill in behind the front as it passes
through each island. Decreasing wind speed trends are forecast 
from Saturday to Sunday. A Small Craft Advisory (SCA) remains in 
effect for select waters around Kauai and Oahu due to lingering 
high seas through this afternoon. A SCA will likely need to be 
issued later today or tonight for the strong winds following the 
second front into Friday.

A slowly declining moderate, medium period northwest (330 degree)
swell is producing low advisory level surf for the north and 
west-facing shores of Niihau, Kauai, and Oahu. Thus, a High Surf 
Advisory remain in effect through tonight. However, will continue 
to monitor the buoys to determine if there is enough support to 
cancel the HSA this afternoon as this swell slowly declines. 

A gale force low is expected to deepen north of Hawaii Thursday,
producing a north to south fetch aimed directly at the islands. 
The close proximity of this source will lead to a large, medium 
period northwest swell (310-320 degrees) swell moving into the 
islands Thursday afternoon. This swell along with an overlapping 
moderate, long period northwest (320 degree) swell may boost surf 
heights to high- end advisory or low- end warning levels Thursday 
night through Friday. The swell direction will shift more 
northerly (350-010 degree) direction late Friday as the fetch area
drifts slowly eastward with the parent low center. Surf along west
facing shores will drop below advisory thresholds Saturday but 
north facing shores will remain in the HSA through Saturday. 
Surf along east facing shores will remain small through the week
with the exception of some areas exposed to north swell wrap. Surf
will remain small for south facing shores. 

High tides will peak over the next few days producing minor 
coastal flooding, however the large north swell run up on top of 
the winter peak high tides from 3 to 4 AM HST will produce 
additional impacts along north facing shores through Saturday 
morning, and the north swell will produce harbor surges in 
Kahului and Hilo Harbors from Friday through Saturday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Thursday for Niihau-Kauai 
Leeward-Waianae Coast-Oahu North Shore-Kauai North-Kauai East.

Small Craft Advisory until 6 AM HST Thursday for Kauai Northwest 
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters.

&&

$$

DISCUSSION...Wroe
AVIATION...Foster
MARINE...Almanza