NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
124
FXHW60 PHFO 260700
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
900 PM HST Sat Jan 25 2025
.SYNOPSIS...
A weak trough near the Big Island this evening will slowly drift
northward as a shallow cold front approaches the islands from the
northwest. These two systems will merge near Kauai and Niihau by
Sunday night producing widespread showers over the Garden Isle.
Breezy and cool northerly winds will fill in behind the front as
it moves down the island chain, stalling out near the Big Island
by Tuesday. Showers will favor windward areas and all areas within
the passing frontal cloud band. Moderate to breezy and cool
northerly winds will fill in as the front passes through each
island. A very wet weather pattern with unstable southerly kona
winds may develop by Thursday.
&&
.DISCUSSION...
Satellite and local radar imagery this evening showed a few
thunderstorms developing in the coastal waters and along the
leeward slopes of the Big Island this evening. These thunderstorms
developed along the lingering stalled low level trough and were
triggered by a passing atmospheric gravity wave. Additional
enhanced showers and a few thunderstorms are possible for the Big
Island this evening, mainly along the north and east slopes of
Mauna Kea. Farther northwest of the state a cold front continues
to approach the island chain. The low level trough near the Big
Island will be slowly drawn northward as this cold front
approachers the state.
Expect light to moderate trade winds to continue through Sunday
morning with some shower activity mainly favoring the windward and
mountain areas. Wetter trends are expected as the cold front
combines forces with the weak low level trough near Kauai from
Sunday night into Monday. Expect widespread showers across the
Garden Isle lasting into Monday morning. Breezy and cool northerly
winds will quickly move in with decreasing shower trends after
this front passes through each island. The arrival timing of the
showers will reach Oahu and the islands in Maui County by Monday
morning, then spread to the Big Island by Monday afternoon. The
cold front will weaken as it passes through each island. Showers
along the frontal band will be more numerous near Kauai with
lesser amounts of rainfall expected to reach the eastern islands
with this event. Thunderstorms may develop just north of the
island chain along the passing frontal boundary. The front will
stall out and diminish near the Big Island by Wednesday with a
brief period of decreasing shower trends in the forecast.
By Thursday the weather conditions are trending towards a much
wetter pattern as a few low pressure systems move quickly through
the Hawaii region. The latest model solutions show the potential
for southerly kona winds to develop over the islands by Thursday
morning. These southerly winds will pull up unstable tropical
moisture northward into the passing cold core lows. This system
has the potential to produce periods of heavy rain and
thunderstorms across the state, elevating flooding threat
potential. However that said forecast challenges remain. Global
models are highly inconsistent from model run to model run, which
means our confidence in these day 5 forecast impacts remains
moderate to low at this time. The time period will need to grow a
little shorter before we can tune into these island by island
potential impacts. Stay tuned to the latest weather forecast
updates with this system as the long range weather picture
becomes clearer early next week.
&&
.AVIATION...
Moderate trades expected. SHRA and low cigs focused over windward
and mauka locations with some limited spillover to leeward areas.
A low level trough over the islands and a new trough moving in
will combine to increase the potential for increased SHRA and low
cigs by late tomorrow especially over the western end of the state.
MVFR conds can be expected in SHRA but otherwise VFR should
prevail.
No AIRMETs currently in effect however with increased potential
for rain over the western end of the state AIRMET Sierra for mtn
obsc may be needed at various times through the rest of the
weekend.
&&
.MARINE...
Light to moderate northeast to east winds will persist into
Sunday as a weak surface ridge remains north of the state. Pockets
of fresh breezes may develop over the typically windier waters
and channels from Maui County to the Big Island during this time.
Fresh to strong northerly breezes are expected over the western
end of the state late Sunday through Monday, then extend down the
island chain late Monday through Tuesday as a front moves into
the area. A Small Craft Advisory will likely be issued later
tonight for the potential of strong northerly winds over the
waters surrounding Oahu and Kauai. Uncertainty increases
Wednesday through the second half of the week, with some solutions
depicting moderate to strong southerly winds developing as low
pressure forms in the area.
Surf along shores exposed to northerly swells has steadily
decreased throughout the day, with heights dropping below average
for this time of year. This trend is expected to continue into
Sunday, before increasing Sunday night through Monday due to a
mix of a small northwest swell and rough, short-period surf
associated with the strong northerly winds following the front
(highest over the western end of the state).
With a blocking high persisting over the northwest Pacific, the
primary swell source will remain from the north throughout the
week, featuring a mix of short-period wind waves from the locally
expected northerly winds and medium-period northerly swells.
Guidance remains in good agreement, indicating an upward trend
Tuesday through late in the week, due to a potential gale- to
storm-force low forming well to the north. Heights could approach
the advisory level Wednesday through Friday if this scenario
materializes.
Surf along east-facing shores, not exposed to northerly swells,
will remain small each day due to the lack of local trades and
upstream swells.
Surf along south-facing shores will remain around the seasonal
average through midweek, with a mix of short-period southeast
swells and occasional background south swells. Uncertainty
increases late in the week, with the aforementioned potential for
southerly winds evolving that could translate to a short window of
rough, short-period surf.
&&
.FIRE WEATHER...
Wind speeds will remain below critical fire weather thresholds
through the middle of next week. Moisture levels rise swiftly from
Thursday onward with southerly winds bringing another round of
widespread rainfall in the forecast for all islands.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Bohlin
AVIATION...Walsh
MARINE...Gibbs
FIRE WEATHER...Bohlin
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office
Narrow the Menu List
Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit
Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special
Hawaiian Islands Synoptic Discussion and Guidance
124
FXHW60 PHFO 260700
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
900 PM HST Sat Jan 25 2025
.SYNOPSIS...
A weak trough near the Big Island this evening will slowly drift
northward as a shallow cold front approaches the islands from the
northwest. These two systems will merge near Kauai and Niihau by
Sunday night producing widespread showers over the Garden Isle.
Breezy and cool northerly winds will fill in behind the front as
it moves down the island chain, stalling out near the Big Island
by Tuesday. Showers will favor windward areas and all areas within
the passing frontal cloud band. Moderate to breezy and cool
northerly winds will fill in as the front passes through each
island. A very wet weather pattern with unstable southerly kona
winds may develop by Thursday.
&&
.DISCUSSION...
Satellite and local radar imagery this evening showed a few
thunderstorms developing in the coastal waters and along the
leeward slopes of the Big Island this evening. These thunderstorms
developed along the lingering stalled low level trough and were
triggered by a passing atmospheric gravity wave. Additional
enhanced showers and a few thunderstorms are possible for the Big
Island this evening, mainly along the north and east slopes of
Mauna Kea. Farther northwest of the state a cold front continues
to approach the island chain. The low level trough near the Big
Island will be slowly drawn northward as this cold front
approachers the state.
Expect light to moderate trade winds to continue through Sunday
morning with some shower activity mainly favoring the windward and
mountain areas. Wetter trends are expected as the cold front
combines forces with the weak low level trough near Kauai from
Sunday night into Monday. Expect widespread showers across the
Garden Isle lasting into Monday morning. Breezy and cool northerly
winds will quickly move in with decreasing shower trends after
this front passes through each island. The arrival timing of the
showers will reach Oahu and the islands in Maui County by Monday
morning, then spread to the Big Island by Monday afternoon. The
cold front will weaken as it passes through each island. Showers
along the frontal band will be more numerous near Kauai with
lesser amounts of rainfall expected to reach the eastern islands
with this event. Thunderstorms may develop just north of the
island chain along the passing frontal boundary. The front will
stall out and diminish near the Big Island by Wednesday with a
brief period of decreasing shower trends in the forecast.
By Thursday the weather conditions are trending towards a much
wetter pattern as a few low pressure systems move quickly through
the Hawaii region. The latest model solutions show the potential
for southerly kona winds to develop over the islands by Thursday
morning. These southerly winds will pull up unstable tropical
moisture northward into the passing cold core lows. This system
has the potential to produce periods of heavy rain and
thunderstorms across the state, elevating flooding threat
potential. However that said forecast challenges remain. Global
models are highly inconsistent from model run to model run, which
means our confidence in these day 5 forecast impacts remains
moderate to low at this time. The time period will need to grow a
little shorter before we can tune into these island by island
potential impacts. Stay tuned to the latest weather forecast
updates with this system as the long range weather picture
becomes clearer early next week.
&&
.AVIATION...
Moderate trades expected. SHRA and low cigs focused over windward
and mauka locations with some limited spillover to leeward areas.
A low level trough over the islands and a new trough moving in
will combine to increase the potential for increased SHRA and low
cigs by late tomorrow especially over the western end of the state.
MVFR conds can be expected in SHRA but otherwise VFR should
prevail.
No AIRMETs currently in effect however with increased potential
for rain over the western end of the state AIRMET Sierra for mtn
obsc may be needed at various times through the rest of the
weekend.
&&
.MARINE...
Light to moderate northeast to east winds will persist into
Sunday as a weak surface ridge remains north of the state. Pockets
of fresh breezes may develop over the typically windier waters
and channels from Maui County to the Big Island during this time.
Fresh to strong northerly breezes are expected over the western
end of the state late Sunday through Monday, then extend down the
island chain late Monday through Tuesday as a front moves into
the area. A Small Craft Advisory will likely be issued later
tonight for the potential of strong northerly winds over the
waters surrounding Oahu and Kauai. Uncertainty increases
Wednesday through the second half of the week, with some solutions
depicting moderate to strong southerly winds developing as low
pressure forms in the area.
Surf along shores exposed to northerly swells has steadily
decreased throughout the day, with heights dropping below average
for this time of year. This trend is expected to continue into
Sunday, before increasing Sunday night through Monday due to a
mix of a small northwest swell and rough, short-period surf
associated with the strong northerly winds following the front
(highest over the western end of the state).
With a blocking high persisting over the northwest Pacific, the
primary swell source will remain from the north throughout the
week, featuring a mix of short-period wind waves from the locally
expected northerly winds and medium-period northerly swells.
Guidance remains in good agreement, indicating an upward trend
Tuesday through late in the week, due to a potential gale- to
storm-force low forming well to the north. Heights could approach
the advisory level Wednesday through Friday if this scenario
materializes.
Surf along east-facing shores, not exposed to northerly swells,
will remain small each day due to the lack of local trades and
upstream swells.
Surf along south-facing shores will remain around the seasonal
average through midweek, with a mix of short-period southeast
swells and occasional background south swells. Uncertainty
increases late in the week, with the aforementioned potential for
southerly winds evolving that could translate to a short window of
rough, short-period surf.
&&
.FIRE WEATHER...
Wind speeds will remain below critical fire weather thresholds
through the middle of next week. Moisture levels rise swiftly from
Thursday onward with southerly winds bringing another round of
widespread rainfall in the forecast for all islands.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Bohlin
AVIATION...Walsh
MARINE...Gibbs
FIRE WEATHER...Bohlin
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office