Area Forecast Discussion
Issued by NWS Honolulu, HI

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367
FXHW60 PHFO 061957
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
957 AM HST Mon Jan 6 2025

.SYNOPSIS...

Gentle to locally breezy southwest winds will gradually
strengthen today across the western end of the state as a front
slowly approaches from the northwest. Clouds and showers will be
focused along kona coasts and slopes. The front is expected to
shift down to island chain Tuesday night before stalling and
dissipating around the Oahu and Maui County Wednesday shifting
clouds and showers along northern exposures. Moderate trades are
expected to return during the second half of the week with clouds
and showers mainly focused along windward and mauka areas. Showers
will remain enhanced as upper level instability increases over
the state.


&&

.DISCUSSION...

Latest satellite and radar imagery show clouds and showers over
kona coasts and slopes as gentle south and southwesterly winds
prevail over the state. Total rainfall accumulations remain light
as weak mid- level riding keeps an inversion layer between 5.5- 6
kft based on the morning sounding. As the day progresses expect
clouds and chances of showers to increase over interior and kona
slopes. This will be partly due to diurnal pattern and the middle
level ridge eroding, allowing for clouds to develop more and
increasing low level moisture. Over the eastern half of the state
gentle south to southwest winds will shift the vog plume mainly
over the Big Island for the next couple of days.

Latest model guidance continues to show an upper level trough
deepening west of the state today and tonight that will
reinvigorate a nearly stationary frontal boundary northwest of
Kauai. Expect southwest winds over the western half of the state
to gradually strengthen becoming breezy late tonight into Tuesday
as the front moves south. Hi resolution model guidance keeps light
to moderate showers focused along kona coasts and slopes. The
front is expected to move over Kauai Tuesday night before
weakening an shifting over Oahu Wednesday. Increased upper level
instability from the trough and low level moisture riding in ahead
of the front will increase chances of precipitation and intensity
from light to moderate to locally heavy mainly for exposed
northern exposures.

Wednesday night into Thursday, amplified upper level ridging to
the east of the state will deepen the upper level trough over
state Thursday into the weekend. Lingering low- level moisture
from the dissipating front will become enhanced as another area of
moisture is advected in from the southeast. This along with the
returning trades as a surface high builds north of the state
behind the front and tracks northeast will keep enhanced
precipitation in the forecast but shift the focus along windward
and mauka areas. The anomalous cold upper level temperatures could
also increase chances for thunderstorms around the upper slopes
of the Big Island Friday and Saturday but have left them out of
the forecast at this time since the probabilities. However, model
guidance is trending up with each model run so bears watching and
mentioning.



&&

.AVIATION...

A cold front is approaching the islands from the northwest and
will remain northwest of the state today. Ahead of this feature,
light to moderate southerly to southwesterly winds will prevail
through Tuesday. Winds may be light enough for localized land and
sea breezes to develop in terrain sheltered areas. Meanwhile, a
pre-frontal convergence band of moisture will continue to produce
clouds and a few showers streaming from the south across Maui
County and Kauai today. The band over Maui County is forecast to
lift northward over Oahu tonight. The front is expected to make
its way across Kauai by late Tuesday, increasing showers and low
clouds as it moves through.

This morning, AIRMET Sierra remains in effect for IFR conditions
at Lanai, where ceilings have been broken to overcast at around
300 feet since midnight. Based on latest satellite trends, the
IFR should lift at Lanai by late morning. Additionally, AIRMET
Sierra also remains in effect for mountain obscuration for SW
through W sections of Kauai, Molokai, and Maui.


&&

.MARINE...
Overlapping significant swell energy will maintain warning level
surf heights along exposed north and west facing shores. The High
Surf Warning (HSW) is now in effect through Wednesday morning for
north and west facing shores of Niihau, Kauai, Oahu, and Molokai,
north facing shores of Maui, and west facing shores of the Big
Island. A Small Craft Advisory (SCA) is also in effect through
Wednesday morning for all Hawaiian coastal waters except Maalea
Bay. Seas 10 ft or greater are expected for all waters exposed
to west and northwest swells. Both the HSW and SCA will likely
need to be extended through at least Thursday.

According to latest model guidance, the current west-northwest
(290-310 degree) swell will hold surf heights just above HSW
criteria through Tuesday. Surf heights will then rapidly climb
with the arrival of an extra-large reinforcing swell out of the
northwest (310-330). The swell is expected to peak by Wednesday
morning then slowly decline. Surf heights along north and west
facing shores should drop back below warning levels no later than
Thursday evening. Surf heights along east and south facing shores
will remain small through the forecast period.

Over the western islands, moderate to fresh southwesterlies will
continue to blow into Tuesday, and then become more northerly
winds from Tuesday night into Wednesday as a weak cold front
moves across the islands. Wind directions will then shift back to
moderate to fresh northeasterly to easterly trade winds by
Thursday. Across the eastern end of the state, gentle to locally
fresh southeast winds will hold today, then become light and
variable by Tuesday before transitioning back to moderate trades
on Thursday.


&&

.FIRE WEATHER...

No critical fire weather conditions are expected through the
forecast period. Gentle to locally breezy southerly flow will
help increase moisture around the state, especially for leeward
areas. A front is expected to move through the western part of
the state late Tuesday through Wednesday, increasing potential
for rainfall. Moderate trades wind will fill in behind the front.
Increasing upper level instability and lingering moisture over
the state will keep an enhanced potential for rainfall over the
state but mainly focused over windward and mauka areas.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 AM HST Wednesday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kona-
Kohala-Kauai North-Molokai Windward-Molokai North-Molokai West-
Maui Central Valley North-Windward Haleakala-Big Island South.

Small Craft Advisory until 6 AM HST Wednesday for all Hawaiian
waters except Maalaea Bay-


&&

$$


DISCUSSION...Almanza
AVIATION...Vaughan
MARINE...Bedal
FIRE WEATHER...Almanza