NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
163
FXHW60 PHFO 181927
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
927 AM HST Sat May 18 2024
.SYNOPSIS...
Showers will continue moving over Kauai County today before the
kona low that has been impacting weather across the islands for
several days begins to slowly drift north and weaken. Increased
showers will also be possible over Oahu this afternoon through
tonight. Expect improving trends from east to west on Sunday. By
Monday all islands will see an improvement in weather conditions
as easterly trade winds return.
&&
.DISCUSSION...
The kona low that has been impacting weather across the state for
the past several days is centered about 850 miles northwest of
Kauai this morning, with a trough located just west of Kauai.
Latest radar and satellite imagery shows isolated thunderstorms
embedded along the main line of convergence just east of the
trough. The band of showers is producing primarily light to
moderate rain over Kauai at this time, though pockets of heavier
rain are still possible today before the kona low begins to shift
away from the state. Therefore, a Flood Watch remains in effect
for Kauai County through tonight. A few showers from this main
band could reach Oahu as well today.
High pressure will slowly build in from east to west across the
state through Sunday as the kona low shifts north and weakens. Of
note, some of the latest hi-res guidance shows that flow around
the Big Island could set up a convergence band downstream,
supporting convective development in the western coastal waters
this afternoon. Given the more southerly flow south of Oahu,
there is the potential for this Big Island plume to move towards
the island of Oahu and increase shower activity there, in
addition to any showers from the main band. This pattern could
also be conducive for showers to develop along the Koolau range
into this evening.
Upper levels continue to show divergence aloft that will keep
some instability over western end of the state. Expect more
stabilizing trends with decreasing showers as east to southeast
winds spread across the state. By Sunday, the moderate to heavy
rainfall threat will diminish over Kauai as more stable conditions
fill in across the state.
Easterly trade winds will return across the islands from Monday
onward. Trade wind showers may be somewhat enhanced during the
first half of next week due to lingering moisture and some upper
level instability from a short wave trough. Precipitable water
values will return to normal during the second half of the week,
supporting a more typical trade wind pattern.
&&
.AVIATION...
A trough just west of Kauai will maintain an unstable environment
especially over the western half of the state. A steady stream of
moisture will continue to impact Kauai today with periods of IFR
conditions possible in moderate to locally heavy showers through
this evening. Lingering instability near Oahu will keep periods
of MVFR conditions in showers. A deep upper level trough will
produce light to moderate turbulence across the state from
FL280-400 through Sunday. AIRMET Tango is in effect across the
state due to the upper level turbulence.
AIRMET Sierra in effect for mountain obscurations over most
islands except Big Island.
Periods of light to moderate rime icing is expected from Kauai to
Oahu in layer 130-FL220 especially this afternoon through tonight.
AIRMET ZULU is in effect.
&&
.MARINE...
Moderate to locally strong east to southeast winds associated
with a kona low far north-northwest of the state will persist
over the weekend. A shift out of a more typical easterly trade
wind direction is expected early next week as it lifts northward
and away from the region and the ridge builds to the north. A Small
Craft Advisory remains in effect for the windier coastal waters
around Maui County and the Big Island through Sunday.
Surf along south facing shores will remain up through early next
week due to overlapping, long-period south-southwest swells. The
first swell will hold around the advisory level today before
briefly lowering Sunday. Offshore buoy observations are holding
strong with the peak energy associated with this swell now into
the 14-16 second bands. The short-period wind chop added from the
southerly winds will linger today, then ease as we transition back
to an east to southeast wind regime by early next week. A fresh,
long-period south-southwest swell will fill in through the day
Sunday, then peak slightly lower than the current swell early next
week before easing Tuesday through midweek.
Surf along north facing shores will steadily lower through the
weekend, with a return to a more typical pattern for this time of
year next week.
Surf along east facing shores will remain well below average
through the weekend. An upward trend is possible next week as the
trades return locally and far upstream over the eastern Pacific.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for Niihau and Kauai.
High Surf Advisory until 6 PM HST this evening for south facing
shores of all islands.
Small Craft Advisory until 6 PM HST Sunday for Maui County
Windward Waters-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Kino
MARINE...JVC
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
163
FXHW60 PHFO 181927
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
927 AM HST Sat May 18 2024
.SYNOPSIS...
Showers will continue moving over Kauai County today before the
kona low that has been impacting weather across the islands for
several days begins to slowly drift north and weaken. Increased
showers will also be possible over Oahu this afternoon through
tonight. Expect improving trends from east to west on Sunday. By
Monday all islands will see an improvement in weather conditions
as easterly trade winds return.
&&
.DISCUSSION...
The kona low that has been impacting weather across the state for
the past several days is centered about 850 miles northwest of
Kauai this morning, with a trough located just west of Kauai.
Latest radar and satellite imagery shows isolated thunderstorms
embedded along the main line of convergence just east of the
trough. The band of showers is producing primarily light to
moderate rain over Kauai at this time, though pockets of heavier
rain are still possible today before the kona low begins to shift
away from the state. Therefore, a Flood Watch remains in effect
for Kauai County through tonight. A few showers from this main
band could reach Oahu as well today.
High pressure will slowly build in from east to west across the
state through Sunday as the kona low shifts north and weakens. Of
note, some of the latest hi-res guidance shows that flow around
the Big Island could set up a convergence band downstream,
supporting convective development in the western coastal waters
this afternoon. Given the more southerly flow south of Oahu,
there is the potential for this Big Island plume to move towards
the island of Oahu and increase shower activity there, in
addition to any showers from the main band. This pattern could
also be conducive for showers to develop along the Koolau range
into this evening.
Upper levels continue to show divergence aloft that will keep
some instability over western end of the state. Expect more
stabilizing trends with decreasing showers as east to southeast
winds spread across the state. By Sunday, the moderate to heavy
rainfall threat will diminish over Kauai as more stable conditions
fill in across the state.
Easterly trade winds will return across the islands from Monday
onward. Trade wind showers may be somewhat enhanced during the
first half of next week due to lingering moisture and some upper
level instability from a short wave trough. Precipitable water
values will return to normal during the second half of the week,
supporting a more typical trade wind pattern.
&&
.AVIATION...
A trough just west of Kauai will maintain an unstable environment
especially over the western half of the state. A steady stream of
moisture will continue to impact Kauai today with periods of IFR
conditions possible in moderate to locally heavy showers through
this evening. Lingering instability near Oahu will keep periods
of MVFR conditions in showers. A deep upper level trough will
produce light to moderate turbulence across the state from
FL280-400 through Sunday. AIRMET Tango is in effect across the
state due to the upper level turbulence.
AIRMET Sierra in effect for mountain obscurations over most
islands except Big Island.
Periods of light to moderate rime icing is expected from Kauai to
Oahu in layer 130-FL220 especially this afternoon through tonight.
AIRMET ZULU is in effect.
&&
.MARINE...
Moderate to locally strong east to southeast winds associated
with a kona low far north-northwest of the state will persist
over the weekend. A shift out of a more typical easterly trade
wind direction is expected early next week as it lifts northward
and away from the region and the ridge builds to the north. A Small
Craft Advisory remains in effect for the windier coastal waters
around Maui County and the Big Island through Sunday.
Surf along south facing shores will remain up through early next
week due to overlapping, long-period south-southwest swells. The
first swell will hold around the advisory level today before
briefly lowering Sunday. Offshore buoy observations are holding
strong with the peak energy associated with this swell now into
the 14-16 second bands. The short-period wind chop added from the
southerly winds will linger today, then ease as we transition back
to an east to southeast wind regime by early next week. A fresh,
long-period south-southwest swell will fill in through the day
Sunday, then peak slightly lower than the current swell early next
week before easing Tuesday through midweek.
Surf along north facing shores will steadily lower through the
weekend, with a return to a more typical pattern for this time of
year next week.
Surf along east facing shores will remain well below average
through the weekend. An upward trend is possible next week as the
trades return locally and far upstream over the eastern Pacific.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for Niihau and Kauai.
High Surf Advisory until 6 PM HST this evening for south facing
shores of all islands.
Small Craft Advisory until 6 PM HST Sunday for Maui County
Windward Waters-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Kino
MARINE...JVC
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office