NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
526
FXHW60 PHFO 151301
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
301 AM HST Wed Jan 15 2025
.SYNOPSIS...
Moderate to locally breezy trades will ease today and tonight.
Trade showers are expected to diminish as well, though some
showers could linger for windward Big Island and Maui through
tonight. A relatively weak and disorganized cold front will push
down the chain Thursday night through Saturday. Unstable air
associated with the front should enhance showers during this
period, with a small chance for a couple rumbles of thunder for
Maui and the Big Island on Friday. More stable and dry air should
fill in behind the front on a rather cool northerly flow which
will shift around to northeast trades over the Holiday weekend.
&&
.DISCUSSION...
Currently at the surface, a 1029 mb high is centered around 1200
miles north-northeast of Honolulu, while a cold front is
positioned around 900 miles west-northwest of Kauai. The
resulting gradient is producing moderate to locally breezy trade
winds across the island chain early this morning. Infrared
satellite imagery shows partly to mostly cloudy conditions in
windward areas as well as leeward sections of the Big Island,
with clear to partly cloudy skies elsewhere. Main short term
focus revolves around trade wind trends and rain chances.
Moderate to locally breezy trades will ease up today through
Thursday as a front approaches from the northwest. The winds will
become light enough to allow land and sea breezes to dominate late
tonight and Thursday. A cold front will then slide southeastward
down the island chain Thursday night through early Saturday.
Light to moderate west to southwest winds will develop in advance
of the front, while moderate northwest to north winds fill in
behind it. The front should have cleared the Big Island by
late Saturday, with moderate to locally breezy northeasterly
trades expected Saturday night through Sunday night as high
pressure builds eastward to the north of the state. The trades
will then ease up again early next week as the next front
approaches the island chain from the northwest.
As for the remaining weather details, fairly typical trade wind
weather will prevail this morning with showers favoring windward
slopes and coasts. Mid-level ridging will build over the islands
reducing shower coverage considerably this afternoon and tonight.
The exception may be over windward Maui and the Big Island where
an area of enhanced moisture appears to move in from the east
bringing an increase in shower activity tonight. Fairly dry and
stable weather will continue on Thursday, with morning showers
favoring windward sections of Maui and the Big Island, with a few
daytime heating showers developing over the interior of the
islands in the afternoon. There remains some uncertainty regarding
the timing and strength of the late week cold front, but overall
we should see an increase in showers in association with the front
as it progresses southeastward down the island chain Thursday
night through Saturday. There is a slight chance for thunderstorms
over the higher terrain of Maui and the Big Island Friday
afternoon, which could bring some wintry precip to the summits of
Mauna Loa and Mauna Kea if they occur. Behind the front drier and
more stable conditions will build in. Fairly dry and stable
conditions should then prevail Saturday night through early next
week, with showers limited primarily to windward slopes and
coasts.
&&
.AVIATION...
Moderate trades slightly weakening through tonight as a cold
front approaches from the northwest. Low cigs and SHRA should be
focused over windward and mauka areas. Brief MVFR conds can be
expected in SHRA but otherwise, VFR should prevail.
No AIRMETs are in effect.
&&
.MARINE...
A cold front and low pressure system passing just north of the
island chain will weaken the trade winds through the day. A light
wind regime with expanding near shore land and sea breezes will
expand in coverage from Thursday through the end of the week. The
cold front will move into the northwestern Hawaiian Islands
Thursday night then slide southeastward down the island chain into
Saturday supported by an upper level trough. Expect numerous
showers with this next system, including the potential for
thunderstorms over the easternmost waters.
The current long period northwest swell will continue to decline
today. The forerunners of the next significant northwest swell
will move into the islands by Thursday night, and then swiftly
build above warning thresholds along exposed north and west facing
shores from late Friday into Saturday, then falling to advisory
thresholds by Sunday. Another medium period northwest swell is
forecast to fill in from Tuesday to Wednesday of next week,
keeping surf heights elevated along north and west facing shores.
Surf along south facing shores will remain very small through
this afternoon. A small long period south swell boost will
develop from tonight into Thursday, peaking by Friday, and slowly
lowering through the weekend. PacIOOS buoy observations located
in American Samoa peaked above model guidance, suggesting surf
may peak near or just below High Surf Advisory levels.
Surf along east facing shores will slowly decline through the end
of the week as trade winds diminish. A small north swell could
potentially elevate surf along exposed shorelines on Wednesday and
Thursday.
&&
.FIRE WEATHER...
No critical fire conditions anticipated during the forecast
period, although we will keep an eye on Saturday and Sunday which
could feature the lowest post-frontal relative humidities and a
relative peak in N or NE winds. For now, both wind speeds and
humidity levels are not expected to reach Red Flag Warning
criteria concurrently, but guidance suggests it may be close,
particularly on Sunday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Jelsema
AVIATION...Walsh
MARINE...Bohlin
FIRE WEATHER...Jelsema
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office
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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
526
FXHW60 PHFO 151301
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
301 AM HST Wed Jan 15 2025
.SYNOPSIS...
Moderate to locally breezy trades will ease today and tonight.
Trade showers are expected to diminish as well, though some
showers could linger for windward Big Island and Maui through
tonight. A relatively weak and disorganized cold front will push
down the chain Thursday night through Saturday. Unstable air
associated with the front should enhance showers during this
period, with a small chance for a couple rumbles of thunder for
Maui and the Big Island on Friday. More stable and dry air should
fill in behind the front on a rather cool northerly flow which
will shift around to northeast trades over the Holiday weekend.
&&
.DISCUSSION...
Currently at the surface, a 1029 mb high is centered around 1200
miles north-northeast of Honolulu, while a cold front is
positioned around 900 miles west-northwest of Kauai. The
resulting gradient is producing moderate to locally breezy trade
winds across the island chain early this morning. Infrared
satellite imagery shows partly to mostly cloudy conditions in
windward areas as well as leeward sections of the Big Island,
with clear to partly cloudy skies elsewhere. Main short term
focus revolves around trade wind trends and rain chances.
Moderate to locally breezy trades will ease up today through
Thursday as a front approaches from the northwest. The winds will
become light enough to allow land and sea breezes to dominate late
tonight and Thursday. A cold front will then slide southeastward
down the island chain Thursday night through early Saturday.
Light to moderate west to southwest winds will develop in advance
of the front, while moderate northwest to north winds fill in
behind it. The front should have cleared the Big Island by
late Saturday, with moderate to locally breezy northeasterly
trades expected Saturday night through Sunday night as high
pressure builds eastward to the north of the state. The trades
will then ease up again early next week as the next front
approaches the island chain from the northwest.
As for the remaining weather details, fairly typical trade wind
weather will prevail this morning with showers favoring windward
slopes and coasts. Mid-level ridging will build over the islands
reducing shower coverage considerably this afternoon and tonight.
The exception may be over windward Maui and the Big Island where
an area of enhanced moisture appears to move in from the east
bringing an increase in shower activity tonight. Fairly dry and
stable weather will continue on Thursday, with morning showers
favoring windward sections of Maui and the Big Island, with a few
daytime heating showers developing over the interior of the
islands in the afternoon. There remains some uncertainty regarding
the timing and strength of the late week cold front, but overall
we should see an increase in showers in association with the front
as it progresses southeastward down the island chain Thursday
night through Saturday. There is a slight chance for thunderstorms
over the higher terrain of Maui and the Big Island Friday
afternoon, which could bring some wintry precip to the summits of
Mauna Loa and Mauna Kea if they occur. Behind the front drier and
more stable conditions will build in. Fairly dry and stable
conditions should then prevail Saturday night through early next
week, with showers limited primarily to windward slopes and
coasts.
&&
.AVIATION...
Moderate trades slightly weakening through tonight as a cold
front approaches from the northwest. Low cigs and SHRA should be
focused over windward and mauka areas. Brief MVFR conds can be
expected in SHRA but otherwise, VFR should prevail.
No AIRMETs are in effect.
&&
.MARINE...
A cold front and low pressure system passing just north of the
island chain will weaken the trade winds through the day. A light
wind regime with expanding near shore land and sea breezes will
expand in coverage from Thursday through the end of the week. The
cold front will move into the northwestern Hawaiian Islands
Thursday night then slide southeastward down the island chain into
Saturday supported by an upper level trough. Expect numerous
showers with this next system, including the potential for
thunderstorms over the easternmost waters.
The current long period northwest swell will continue to decline
today. The forerunners of the next significant northwest swell
will move into the islands by Thursday night, and then swiftly
build above warning thresholds along exposed north and west facing
shores from late Friday into Saturday, then falling to advisory
thresholds by Sunday. Another medium period northwest swell is
forecast to fill in from Tuesday to Wednesday of next week,
keeping surf heights elevated along north and west facing shores.
Surf along south facing shores will remain very small through
this afternoon. A small long period south swell boost will
develop from tonight into Thursday, peaking by Friday, and slowly
lowering through the weekend. PacIOOS buoy observations located
in American Samoa peaked above model guidance, suggesting surf
may peak near or just below High Surf Advisory levels.
Surf along east facing shores will slowly decline through the end
of the week as trade winds diminish. A small north swell could
potentially elevate surf along exposed shorelines on Wednesday and
Thursday.
&&
.FIRE WEATHER...
No critical fire conditions anticipated during the forecast
period, although we will keep an eye on Saturday and Sunday which
could feature the lowest post-frontal relative humidities and a
relative peak in N or NE winds. For now, both wind speeds and
humidity levels are not expected to reach Red Flag Warning
criteria concurrently, but guidance suggests it may be close,
particularly on Sunday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Jelsema
AVIATION...Walsh
MARINE...Bohlin
FIRE WEATHER...Jelsema
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office