NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
032
FXHW60 PHFO 221300
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
300 AM HST Thu May 22 2025
.SYNOPSIS...
High pressure will meander far northwest of Hawaii through
Saturday, keeping moderate to locally breezy trades blowing. A low
aloft will enhance incoming trade wind showers today through
Friday. A few downpours are possible, and a rumble or two of
thunder can't be ruled out, mainly for Kauai and Oahu which will
be closest to the upper low. The holiday weekend will trend much
drier and more settled as the upper low moves away. The drier
weather will continue through the middle of next week with the
trade winds easing a bit.
&&
.DISCUSSION...
Currently at the surface, a 1034 mb high is centered around 1250
miles north-northwest of Honolulu, and is driving moderate to
locally breezy trade winds across the island chain early this
morning. Infrared satellite imagery shows partly to mostly cloudy
conditions across the state, with cloud coverage the greatest
over windward and mauka areas. Radar imagery shows scattered to
numerous showers moving into windward slopes and coasts, with a
few showers occasionally reaching leeward communities. Main short
term focus continues to revolve around rain chances and thunder
potential.
High pressure will remain anchored to the north-northwest of the
state today and tonight, then reposition to the northwest of the
islands Friday through the weekend. This will maintain moderate
to locally breezy trade winds across the island chain. The high
will weaken and the associated ridge extending eastward from the
high will settle southward and closer to the state Memorial Day
through the middle of next week, resulting in an easing of the
trade wind flow back to moderate speeds.
As for the remaining weather details, an upper level low currently
evident in water vapor imagery around 250 miles north-northwest of
Kauai, will pivot southeastward and over the western islands later
today. This feature will remain nearly stationary in the vicinity
of Kauai and Oahu tonight, then begin to lift northeastward on
Friday. As the upper level low pivots over the western end of the
state, model solutions continue to depict surface based CAPE
values climbing to around 1000-1500 J/KG and H7-H5 lapse rates
increasing to 6.5-7.0 C/KM. This appears sufficient to bring some
locally heavy downpours in trade showers to the western islands,
with a few rumbles of thunder not out of the question as well.
Some thunder may affect the Big Island slopes this afternoon,
similar to what was seen yesterday. Otherwise, a wetter than
normal trade wind pattern should prevail during the next couple
days, favoring windward and mauka areas, along with more leeward
spread to the shower activity.
The upper low will continue to lift northeastward and away from
the islands Friday night and Saturday, although lingering moisture
will likely keep a somewhat showery trade wind pattern in place.
The airmass will further stabilize Sunday and Memorial Day,
leading to a decrease in trade showers, with fairly typical or
slightly drier than normal conditions then expected through the
middle of next week.
&&
.AVIATION...
Moderate to locally breezy trade winds will persist during the
next 24 hours, strongest and most gusty during the late morning
and afternoon hours. A low aloft will move over the western end of
the state, bringing the potential for a few downpours mainly to
windward areas, with a few rumbles of thunder not out of the
question. A thunderstorm or two may pop over the high elevation
slopes of the Big Island this afternoon as well.
AIRMET Sierra remains in effect for mountain obscuration over
windward portions of Kauai, Oahu, Molokai and Maui. Conditions
will likely improve later this morning on Molokai and Maui, but
may linger through much of the day on Kauai. Oahu may see some
improvement, but confidence in this occurring is not as high as
over the islands further east.
&&
.MARINE...
A broad ridge of high pressure will remain nearly stationary
north of the state, maintaining moderate to locally strong trade
winds through the weekend. An upper level low will build over the
northern waters today enhancing trade showers and may produce
isolated thunderstorms, mainly over Kauai and Oahu waters, through
Friday. The Small Craft Advisory for the windier waters and
channels around Maui County and the Big Island has been extended
through Friday and now includes windier zones around Kauai and
Maui County as winds are expected to strengthen slightly today.
Surf along south facing shores will remain small to moderate as
a long period south-southwest swell is expected to fill in today.
A second pulse from the same direction will fill in over the
weekend and keep small to moderate surf through the weekend before
declining early next week.
East shore surf will remain near seasonal average during the next
couple of days as trade winds persist. Tiny surf will prevail
along north facing shores this week and into the weekend.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Kauai Leeward Waters.
Small Craft Advisory until 6 AM HST Friday for Kaiwi Channel-
Maui County Windward Waters.
Small Craft Advisory until 6 PM HST Friday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...Jelsema
AVIATION...Jelsema
MARINE...Almanza
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
032
FXHW60 PHFO 221300
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
300 AM HST Thu May 22 2025
.SYNOPSIS...
High pressure will meander far northwest of Hawaii through
Saturday, keeping moderate to locally breezy trades blowing. A low
aloft will enhance incoming trade wind showers today through
Friday. A few downpours are possible, and a rumble or two of
thunder can't be ruled out, mainly for Kauai and Oahu which will
be closest to the upper low. The holiday weekend will trend much
drier and more settled as the upper low moves away. The drier
weather will continue through the middle of next week with the
trade winds easing a bit.
&&
.DISCUSSION...
Currently at the surface, a 1034 mb high is centered around 1250
miles north-northwest of Honolulu, and is driving moderate to
locally breezy trade winds across the island chain early this
morning. Infrared satellite imagery shows partly to mostly cloudy
conditions across the state, with cloud coverage the greatest
over windward and mauka areas. Radar imagery shows scattered to
numerous showers moving into windward slopes and coasts, with a
few showers occasionally reaching leeward communities. Main short
term focus continues to revolve around rain chances and thunder
potential.
High pressure will remain anchored to the north-northwest of the
state today and tonight, then reposition to the northwest of the
islands Friday through the weekend. This will maintain moderate
to locally breezy trade winds across the island chain. The high
will weaken and the associated ridge extending eastward from the
high will settle southward and closer to the state Memorial Day
through the middle of next week, resulting in an easing of the
trade wind flow back to moderate speeds.
As for the remaining weather details, an upper level low currently
evident in water vapor imagery around 250 miles north-northwest of
Kauai, will pivot southeastward and over the western islands later
today. This feature will remain nearly stationary in the vicinity
of Kauai and Oahu tonight, then begin to lift northeastward on
Friday. As the upper level low pivots over the western end of the
state, model solutions continue to depict surface based CAPE
values climbing to around 1000-1500 J/KG and H7-H5 lapse rates
increasing to 6.5-7.0 C/KM. This appears sufficient to bring some
locally heavy downpours in trade showers to the western islands,
with a few rumbles of thunder not out of the question as well.
Some thunder may affect the Big Island slopes this afternoon,
similar to what was seen yesterday. Otherwise, a wetter than
normal trade wind pattern should prevail during the next couple
days, favoring windward and mauka areas, along with more leeward
spread to the shower activity.
The upper low will continue to lift northeastward and away from
the islands Friday night and Saturday, although lingering moisture
will likely keep a somewhat showery trade wind pattern in place.
The airmass will further stabilize Sunday and Memorial Day,
leading to a decrease in trade showers, with fairly typical or
slightly drier than normal conditions then expected through the
middle of next week.
&&
.AVIATION...
Moderate to locally breezy trade winds will persist during the
next 24 hours, strongest and most gusty during the late morning
and afternoon hours. A low aloft will move over the western end of
the state, bringing the potential for a few downpours mainly to
windward areas, with a few rumbles of thunder not out of the
question. A thunderstorm or two may pop over the high elevation
slopes of the Big Island this afternoon as well.
AIRMET Sierra remains in effect for mountain obscuration over
windward portions of Kauai, Oahu, Molokai and Maui. Conditions
will likely improve later this morning on Molokai and Maui, but
may linger through much of the day on Kauai. Oahu may see some
improvement, but confidence in this occurring is not as high as
over the islands further east.
&&
.MARINE...
A broad ridge of high pressure will remain nearly stationary
north of the state, maintaining moderate to locally strong trade
winds through the weekend. An upper level low will build over the
northern waters today enhancing trade showers and may produce
isolated thunderstorms, mainly over Kauai and Oahu waters, through
Friday. The Small Craft Advisory for the windier waters and
channels around Maui County and the Big Island has been extended
through Friday and now includes windier zones around Kauai and
Maui County as winds are expected to strengthen slightly today.
Surf along south facing shores will remain small to moderate as
a long period south-southwest swell is expected to fill in today.
A second pulse from the same direction will fill in over the
weekend and keep small to moderate surf through the weekend before
declining early next week.
East shore surf will remain near seasonal average during the next
couple of days as trade winds persist. Tiny surf will prevail
along north facing shores this week and into the weekend.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Kauai Leeward Waters.
Small Craft Advisory until 6 AM HST Friday for Kaiwi Channel-
Maui County Windward Waters.
Small Craft Advisory until 6 PM HST Friday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...Jelsema
AVIATION...Jelsema
MARINE...Almanza
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office