336
FXHW60 PHFO 050133
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
333 PM HST Wed Dec 4 2024

.SYNOPSIS...
The combination of southerly winds, moisture ahead of an
approaching front, and upper troughing will increase rainfall
chances for portions of the state tonight through the second half
of the week. The front will reach Kauai tomorrow, then stall and
begin to diminish near Oahu tomorrow night into Friday. Breezy
north-northeast winds will fill in behind it tomorrow and tomorrow
night. Trades will return briefly on Friday. A second front
passing north of the area over the weekend could cause trades to
weaken again.

&&

.DISCUSSION...
The subtropical ridge has been pushed south across the islands,
resulting in southerly flow across the western portion of the
chain and southeasterlies farther to the east. A ragged 400 mile
wide band of broken to overcast layered clouds northwest of Kauai
marks an approaching front. As this front continues its approach,
rainfall will increase tonight, especially across the western
islands, as upper troughing digs southward into the area. The
combination of southerly winds and lift ahead of the approaching
front could trigger pre-frontal showers. Radar and satellite loops
show this potential, with increased cloud cover and developing
showers noted over and around Oahu and Kauai. Instability will
increase tonight over and around Kauai as the front draws closer.
Thunderstorms can`t be completely ruled out tonight into Thursday,
especially around Kauai.

Models show the front will stall and slowly diminish around Oahu
Thursday night through Friday as the upper trough lifts
northeastward and away from the area. Breezy north to north-
northeast winds behind the front tomorrow and tomorrow night over
the western end of the state will veer out of the east on Friday.
This will push residual frontal moisture westward. A brief return
of light trade winds is possible over the weekend as another
front passes to the north.

&&

.AVIATION...
A few showers embedded within light southerly flow will approach
southwestern Kauai during the next few hours and may graze
portions of western Oahu as well. These showers may bring a brief
deterioration to MVFR on an isolated basis. Otherwise, high
stability and VFR prevail into tonight as southerlies in advance
of an approaching front strengthen sufficiently to offset land
breeze potential in most locations. A solid band of moisture
along the front will bring MVFR clouds and showers to Kauai,
particularly the west and south-facing slopes, late tonight into
Thursday morning. Kauai and Oahu see a transition to NNE trades in
the wake of the front on Thursday afternoon.

No AIRMETs in effect. AIRMET Sierra will likely be needed for
portions of Kauai late tonight into early Thursday morning.

&&

.MARINE...
A near east-to-west surface ridge axis laying across the waters is
supporting statewide light to gentle variable breezes. The ridge
orientation will generally provide south southwest winds over the
Kauai and Oahu coastal waters, variable or south around breezes
Maui and south southeasterlies around Big Island. The eastern
passage of an upper trough to the north will displace ridging to
the east on Friday. It will also push a surface cold front into
the local western waters. This front is timed to reach Kauai`s
nearshore waters tomorrow (Thursday) morning and stall out
somewhere over the central waters Friday into Saturday. Thus,
expect brief period strong north northeast post-frontal winds to
impact Kauai`s surrounding waters Thursday afternoon with
northerlies significantly dropping off as the front passes in
the vicinity of Oahu Thursday evening. The approaching front will
introduce a slight chance of thunderstorms for those waters
surrounding Niihau, Kauai and the Kauai Channel from the early
Thursday morning hours through the afternoon tomorrow. Winds
and/or seas will likely reach Small Craft Advisory (SCA) criteria
Thursday and Friday, focused over the western half of the state,
from the frontal passage in tandem with a passing northwest swell.
The front will weaken as it becomes more zonal in direction
Friday afternoon. Gentle to moderate trade flow will establish
itself going into Saturday. Trades will strengthen to fresh to
locally strong magnitudes by next Tuesday into Wednesday as
surface high pressure builds in northeast of the island chain.

The ongoing short period, near 7 foot swell will hold through the
next north northwest swell arrival tomorrow. Long fetches
produced within very large areas of near-gale to gale-force winds
in association with low pressure systems passing far north of the
area will send north to northwest swell of varying sizes and
periods toward the islands the next several days. Most of this
swell energy will be confined to the relatively shorter period
bands. Resultant surf is expected to be near or above HSA heights
along exposed north and west-facing shores going into the weekend.

A long period, very small south swell will gradually decline
through tomorrow (Thursday). Another similar south swell is
expected from Friday afternoon through the weekend, but it will
may come in a touch smaller than this most recent swell.

&&

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

&&

$$

DISCUSSION...Powell
AVIATION...JVC
MARINE...Blood