NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
200
FXHW60 PHFO 190703
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
900 PM HST Sat Jan 18 2025
.SYNOPSIS...
Post-frontal dry and stable conditions dominate the Hawaiian
Island weather regime through Sunday. Today's northerly winds are
transitioning to traditional trade wind flow. Gentle to locally
breezy trades will persist through Tuesday afternoon. Shower
activity will favor windward and mauka areas Monday and Tuesday. A
major mid week pattern change may develop in response to an
evolving northern upper trough digging south toward the islands.
This will increase precipitation chances although uncertainty
remains high regarding its potential impact upon regional winds
and rainfall distribution.
&&
.DISCUSSION...
A fantastic day across the islands as the region remains under a
dry air mass and gentle northerly breezes. Surface observations
have many communities enjoying early evening middle 60s to lower
70s, with middle 50 to lower 60 dew points, under partly cloudy
skies. With the exception of higher vog concentrations south of
Halema'uma'u crater over Big Island's Ka'u region, skies will
remain mainly clear with the occasional band of windward cumulus
streaming by to the south. University of Hawaii vog modeling
shows that SO2 emissions should remain focused over the south and
east-facing slopes of Big Island through early next week, with
lighter concentrations wrapping around into the leeward Kona
regions. Due to enhanced trades, SO2 emissions are not expected to
reach any of the smaller islands the next couple of days.
Returning trade winds will wring out what little moisture is in
this resident air mass along the windward mauka slopes overnight.
Other than a sprinkle here or there in the higher elevations,
statewide weather will remain dry through Sunday afternoon.
Sunday's weather will be very similar to today's with a cooler
morning in the average middle 60s leading to a comfortably warm
day in upper 70s to lower 80s at or near coast, low to mid 60s
above a few thousand feet elevation. Surface high pressure
establishing itself north northeast of the island chain will
create a tight enough gradient back toward the islands to produce
a few days of gentle to breezy trades. A subtle increase in lower
to middle layer moisture advancing in from the north will
introduce more areal showers to the typically wetter windward
areas and mauka slopes. Mid to upper level ridging nosing in from
the west will maintain enough background stability, in tandem with
slightly lower than seasonable precipitable waters, to limit any
widespread significant rainfall through Tuesday.
The general model consensus going into the middle of next week
depicts falling heights downstream of a deepening Central Pacific
upper trough diving south toward the state. While there is less
inconsistency between the GFS and EC solutions, the signal is
there for a weather regime change Wednesday through Friday.
Uncertainty in this Day 4 into 5 more wet and windy scenario
remains moderate regarding the development and timing of this
trough's mid to late week impact upon the islands. There is a
possibility that a closed off low will develop in the base of the
trough as it reaches our far northern offshore waters late
Wednesday into Thursday. If this does evolve than all chips remain
on the table concerning a myriad of higher rain accumulations,
strong winds with vicinity thunderstorms situations all dependent
upon the movement (or retrogradation) of a large cut-off low
north of the state.
&&
.AVIATION...
VFR conditions will prevail, with moderate northeast trades
and scattered low clouds over windward areas. No AIRMETs are
expected.
&&
.MARINE...
A high pressure system passing just north of the Hawaiian Islands
will keep gentle to fresh trade winds in the forecast through
Tuesday. A weakening cold front moving into the islands on
Wednesday will produce more variable winds along and east of the
frontal band, with northwesterly winds building in behind the
front as it passes through each island. A wet weather pattern
remains in the forecast with chances for some thunderstorm
activity.
The current long period northwest swell will steadily decline
through Sunday. Surf heights along north and west facing shores
will steadily decrease in line with this decreasing swell energy.
through the rest of the weekend along north and west facing
shores. The High Surf Advisory along exposed north and west facing
shores will likely be cancelled by Sunday afternoon as surf
heights are expected to fall below our advisory thresholds. The
next northwest swell may produce advisory level surf along exposed
north and west facing shores from Tuesday into Wednesday.
East-facing shore surf will become more choppy the next couple of
days as the trades build, and background south swell will keep
surf small on south facing shores through the coming week.
The Small Craft Advisory (SCA) remains in effect for waters
surrounding Kauai, including windier waters around Maui and the
Big Island. This SCA will be scaled back by Sunday morning to the
typical windy zones around Maui and Big Island.
&&
.FIRE WEATHER...
Drier air will continue to move across the state through tomorrow,
keeping minimum afternoon relative humidity values at near critical
thresholds. However, winds look to remain just weak enough to
preclude critical fire weather conditions. While daytime more
leeward wind protected humidities may dip into the upper forties at
times the next few days, winds should remain on the low side of 20
mph. Thus, the likelihood for critical fire weather conditions
remains relatively low through Tuesday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Sunday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai
North-Molokai Windward-Molokai North-Molokai West-Maui Central
Valley North-Windward Haleakala.
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel.
Small Craft Advisory until 6 AM HST Monday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Southeast Waters.
&&
$$
DISCUSSION...Blood
AVIATION...Gibbs
MARINE...Bohlin
FIRE...Blood
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
200
FXHW60 PHFO 190703
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
900 PM HST Sat Jan 18 2025
.SYNOPSIS...
Post-frontal dry and stable conditions dominate the Hawaiian
Island weather regime through Sunday. Today's northerly winds are
transitioning to traditional trade wind flow. Gentle to locally
breezy trades will persist through Tuesday afternoon. Shower
activity will favor windward and mauka areas Monday and Tuesday. A
major mid week pattern change may develop in response to an
evolving northern upper trough digging south toward the islands.
This will increase precipitation chances although uncertainty
remains high regarding its potential impact upon regional winds
and rainfall distribution.
&&
.DISCUSSION...
A fantastic day across the islands as the region remains under a
dry air mass and gentle northerly breezes. Surface observations
have many communities enjoying early evening middle 60s to lower
70s, with middle 50 to lower 60 dew points, under partly cloudy
skies. With the exception of higher vog concentrations south of
Halema'uma'u crater over Big Island's Ka'u region, skies will
remain mainly clear with the occasional band of windward cumulus
streaming by to the south. University of Hawaii vog modeling
shows that SO2 emissions should remain focused over the south and
east-facing slopes of Big Island through early next week, with
lighter concentrations wrapping around into the leeward Kona
regions. Due to enhanced trades, SO2 emissions are not expected to
reach any of the smaller islands the next couple of days.
Returning trade winds will wring out what little moisture is in
this resident air mass along the windward mauka slopes overnight.
Other than a sprinkle here or there in the higher elevations,
statewide weather will remain dry through Sunday afternoon.
Sunday's weather will be very similar to today's with a cooler
morning in the average middle 60s leading to a comfortably warm
day in upper 70s to lower 80s at or near coast, low to mid 60s
above a few thousand feet elevation. Surface high pressure
establishing itself north northeast of the island chain will
create a tight enough gradient back toward the islands to produce
a few days of gentle to breezy trades. A subtle increase in lower
to middle layer moisture advancing in from the north will
introduce more areal showers to the typically wetter windward
areas and mauka slopes. Mid to upper level ridging nosing in from
the west will maintain enough background stability, in tandem with
slightly lower than seasonable precipitable waters, to limit any
widespread significant rainfall through Tuesday.
The general model consensus going into the middle of next week
depicts falling heights downstream of a deepening Central Pacific
upper trough diving south toward the state. While there is less
inconsistency between the GFS and EC solutions, the signal is
there for a weather regime change Wednesday through Friday.
Uncertainty in this Day 4 into 5 more wet and windy scenario
remains moderate regarding the development and timing of this
trough's mid to late week impact upon the islands. There is a
possibility that a closed off low will develop in the base of the
trough as it reaches our far northern offshore waters late
Wednesday into Thursday. If this does evolve than all chips remain
on the table concerning a myriad of higher rain accumulations,
strong winds with vicinity thunderstorms situations all dependent
upon the movement (or retrogradation) of a large cut-off low
north of the state.
&&
.AVIATION...
VFR conditions will prevail, with moderate northeast trades
and scattered low clouds over windward areas. No AIRMETs are
expected.
&&
.MARINE...
A high pressure system passing just north of the Hawaiian Islands
will keep gentle to fresh trade winds in the forecast through
Tuesday. A weakening cold front moving into the islands on
Wednesday will produce more variable winds along and east of the
frontal band, with northwesterly winds building in behind the
front as it passes through each island. A wet weather pattern
remains in the forecast with chances for some thunderstorm
activity.
The current long period northwest swell will steadily decline
through Sunday. Surf heights along north and west facing shores
will steadily decrease in line with this decreasing swell energy.
through the rest of the weekend along north and west facing
shores. The High Surf Advisory along exposed north and west facing
shores will likely be cancelled by Sunday afternoon as surf
heights are expected to fall below our advisory thresholds. The
next northwest swell may produce advisory level surf along exposed
north and west facing shores from Tuesday into Wednesday.
East-facing shore surf will become more choppy the next couple of
days as the trades build, and background south swell will keep
surf small on south facing shores through the coming week.
The Small Craft Advisory (SCA) remains in effect for waters
surrounding Kauai, including windier waters around Maui and the
Big Island. This SCA will be scaled back by Sunday morning to the
typical windy zones around Maui and Big Island.
&&
.FIRE WEATHER...
Drier air will continue to move across the state through tomorrow,
keeping minimum afternoon relative humidity values at near critical
thresholds. However, winds look to remain just weak enough to
preclude critical fire weather conditions. While daytime more
leeward wind protected humidities may dip into the upper forties at
times the next few days, winds should remain on the low side of 20
mph. Thus, the likelihood for critical fire weather conditions
remains relatively low through Tuesday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Sunday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai
North-Molokai Windward-Molokai North-Molokai West-Maui Central
Valley North-Windward Haleakala.
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel.
Small Craft Advisory until 6 AM HST Monday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Southeast Waters.
&&
$$
DISCUSSION...Blood
AVIATION...Gibbs
MARINE...Bohlin
FIRE...Blood
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office