NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
328
FXHW60 PHFO 171344
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
344 AM HST Sat May 17 2025
.SYNOPSIS...
A complex upper-level low over the islands will produce unsettled
weather with moderate wet trades prevailing for the next several
days. Heaviest showers will impact primarily windward and
mountain areas, though leeward sides may also see brief periods
of showers. Expect only slight variations in shower activity
throughout the forecast period.
&&
.DISCUSSION...
The latest water vapor imagery coincides with model guidance
showcasing a complex upper-level low centered over the islands
producing unsettled weather across the region. The upper-level
soundings from this morning's 2 AM HST (12z) balloon launch at
Hilo and Lihue demonstrates that the temperature inversion sits at
around 10,000 feet and near 8,000 feet respectively, allowing for
continued bands of showers to rummage through the state,
especially in the vicinity of Kauai and Oahu this morning. While
the heaviest showers will mainly impact the windward and mountain
portions of the islands, brief periods of leeward side showers
cannot be ruled out.
Current satellite imagery displays another band of showers and
clouds is approaching the islands from the east over the next
several hours, however this cloud band will likely only impact
the smaller islands from the late morning into the afternoon
hours. Otherwise weather impacts on Saturday will hold very
similar traits with only subtle wind direction shifts veering a
bit more from the ESE direction while decreasing in strength over
the weekend. While showers remain slightly pulse-y this morning,
anticipate more organized plumes of mostly light to locally
moderate rain this afternoon.
The previously mentioned complex upper-level low remains quasi-
stationary throughout the weekend and into next week with only
slight variations in day by day shower activity across the island
chain. Trades are expected to decrease slightly to more moderate
levels from Saturday onward into early next week. Shower trends
will also decrease in coverage a bit from Sunday to Tuesday across
most islands as the upper low briefly weakens. Another upper low
moves in over the islands on Wednesday with increasing shower
trends for the second half of next week.
&&
.AVIATION...
Moderate to locally breezy trades will decrease slightly this
weekend, with an upper-level disturbance enhancing shower activity
primarily for windward and mountain portions of the island chain.
Expect VFR condition to prevail for most locations, with periods
of MVFR conditions to remain possible in any showers.
AIRMET Sierra remains in effect this morning for mountain
obscuration along northern through eastern sections of Kauai.
&&
.MARINE...
Strong high pressure will remain anchored northeast of the state
through early next week. A developing trough to the distant
northwest is expected to ease the trades tonight into early next
week. Light to moderate trades are expected through the middle of
next week over the western islands, while moderate to fresh
trades are likely to persist over the eastern end of the state. A
Small Craft Advisory (SCA) has been scaled back this morning to
the windier waters around Maui and the Big Island through 6 pm
today.
Surf along north and west-facing shores will remain very small
during the next 7 days. Surf along south-facing shores will hold
at background levels through today. A series of small south and
south-southwest swells will give a small boost to south shore surf
Sunday with a further boost up to the seasonal average possible
during the middle to latter part of next week.
Surf along east-facing shores will hold close to seasonal normals
during the next 7 days.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST this evening for windier
waters and channels around Maui and Big Island.
&&
$$
DISCUSSION...Pierce/Bohlin
AVIATION...Pierce/Bohlin
MARINE...Shigesato
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
328
FXHW60 PHFO 171344
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
344 AM HST Sat May 17 2025
.SYNOPSIS...
A complex upper-level low over the islands will produce unsettled
weather with moderate wet trades prevailing for the next several
days. Heaviest showers will impact primarily windward and
mountain areas, though leeward sides may also see brief periods
of showers. Expect only slight variations in shower activity
throughout the forecast period.
&&
.DISCUSSION...
The latest water vapor imagery coincides with model guidance
showcasing a complex upper-level low centered over the islands
producing unsettled weather across the region. The upper-level
soundings from this morning's 2 AM HST (12z) balloon launch at
Hilo and Lihue demonstrates that the temperature inversion sits at
around 10,000 feet and near 8,000 feet respectively, allowing for
continued bands of showers to rummage through the state,
especially in the vicinity of Kauai and Oahu this morning. While
the heaviest showers will mainly impact the windward and mountain
portions of the islands, brief periods of leeward side showers
cannot be ruled out.
Current satellite imagery displays another band of showers and
clouds is approaching the islands from the east over the next
several hours, however this cloud band will likely only impact
the smaller islands from the late morning into the afternoon
hours. Otherwise weather impacts on Saturday will hold very
similar traits with only subtle wind direction shifts veering a
bit more from the ESE direction while decreasing in strength over
the weekend. While showers remain slightly pulse-y this morning,
anticipate more organized plumes of mostly light to locally
moderate rain this afternoon.
The previously mentioned complex upper-level low remains quasi-
stationary throughout the weekend and into next week with only
slight variations in day by day shower activity across the island
chain. Trades are expected to decrease slightly to more moderate
levels from Saturday onward into early next week. Shower trends
will also decrease in coverage a bit from Sunday to Tuesday across
most islands as the upper low briefly weakens. Another upper low
moves in over the islands on Wednesday with increasing shower
trends for the second half of next week.
&&
.AVIATION...
Moderate to locally breezy trades will decrease slightly this
weekend, with an upper-level disturbance enhancing shower activity
primarily for windward and mountain portions of the island chain.
Expect VFR condition to prevail for most locations, with periods
of MVFR conditions to remain possible in any showers.
AIRMET Sierra remains in effect this morning for mountain
obscuration along northern through eastern sections of Kauai.
&&
.MARINE...
Strong high pressure will remain anchored northeast of the state
through early next week. A developing trough to the distant
northwest is expected to ease the trades tonight into early next
week. Light to moderate trades are expected through the middle of
next week over the western islands, while moderate to fresh
trades are likely to persist over the eastern end of the state. A
Small Craft Advisory (SCA) has been scaled back this morning to
the windier waters around Maui and the Big Island through 6 pm
today.
Surf along north and west-facing shores will remain very small
during the next 7 days. Surf along south-facing shores will hold
at background levels through today. A series of small south and
south-southwest swells will give a small boost to south shore surf
Sunday with a further boost up to the seasonal average possible
during the middle to latter part of next week.
Surf along east-facing shores will hold close to seasonal normals
during the next 7 days.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST this evening for windier
waters and channels around Maui and Big Island.
&&
$$
DISCUSSION...Pierce/Bohlin
AVIATION...Pierce/Bohlin
MARINE...Shigesato
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office