NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
053
FXHW60 PHFO 170202
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
402 PM HST Thu May 16 2024
.SYNOPSIS...
A kona low north of the state will continue drawing unstable
tropical moisture northward over the islands over the next couple
of days. Bands of showers producing moderate to heavy rain and
isolated thunderstorms will move over the central and western
islands tonight through at least Friday. The kona low will begin
to drift away from the state this weekend with improving trends
over the eastern islands, while enhanced rainfall will linger over
the western end of the state into Sunday. All islands will see an
improvement in weather conditions next week as trade winds
gradually return.
&&
.DISCUSSION...
A kona low currently centered roughly 650 nautical miles north-
northwest of Kauai and will continue to impact the state over the
next couple of days. Latest surface analysis this afternoon
continues to show a dying stationary front stretching from the
kona low into the Kauai Channel near the North Shore of Oahu. An
additional surface trough is located roughly 50 miles north of
Kauai.
Surface observations ahead of the frontal boundary show southerly
kona winds that are bringing unstable, deep tropical moisture
from the tropics over the islands. CIMMS MIMIC Layer precipitable
water continues to show PW values from roughly 1.5 to 2.20 inches
across the state. Latest radar imagery this afternoon shows that
light to moderate rain, with occasional pockets of heavier
rain, are moving across the smaller islands, especially Oahu
where surface convergence is maximized. Throughout the day, radar
trends and observed rainfall amounts have fallen a bit short of
what hi-res model guidance would have suggested, limiting overall
flooding impacts to nuisance ponding on roadways, ponding in low-
lying areas, and brief rises in stream levels. For the Big
Island, afternoon convection has produced isolated heavy rain over
the upper North Hilo and South Hilo Districts as well.
With that said, we are still expecting additional impacts tonight
through at least late Friday. Overnight, we are expecting the axis
of heaviest rainfall potential to shift westward back over Oahu
and eventually to focus on Kauai on Friday. As showers train over
already saturated areas, flash flooding will be possible and
streams will become more responsive to downpours. Based on the
latest guidance, the Flood Watch has been cancelled for the
islands of Kahoolawe and Maui since the main impacts are expected
farther west. Therefore, a Flood Watch remains in effect for
Niihau, Kauai, Oahu, Molokai, and Lanai.
Although enhanced rainfall is expected to linger near the western
end of the state throughout the weekend, drier and more stable
east to southeasterly winds will begin to move into the region as
a ridge builds from the east and the kona low drifts northward.
Easterly trade winds will begin to return by the middle of next
week.
&&
.AVIATION...
A strong kona low NNW of Kauai is pulling tropical moisture out
of the south across the state. This will keep the the islands in
an active weather pattern through the remainder of the week into
the weekend. Moderate to heavy SHRA and possible TS are expected
over the western side of the state today and tomorrow. On the Big
Island, SHRA is expected this afternoon into the evening hours.
IFR/MVFR conds expected across the smaller islands especially in
heavier SHRA/TS.
AIRMET Sierra is in effect for for mtn obsc for Kauai, Oahu,
Molokai, Lanai, Maui and windward Big Island.
AIRMET Sierra for IFR conds over Kauai, Oahu, Molokai and Lanai.
AIRMET Tango is in effect for turb blw 120 N thru E of the Big
Island.
AIRMET Zulu is in effect for light rime icing from Kauai to Maui
in layer 140-FL250.
&&
.MARINE...
Strong south to southeast winds associated with a kona low north-
northwest of the state will persist through Friday for most
waters. A shift out of the east to southeast is expected over the
weekend through early next week as the low lifts northward and
away from the area. A Small Craft Advisory remains in effect for
windward and leeward Big Island waters (Hamakua Coast and waters
near South Point). Expect rough seas in heavy showers or
thunderstorms that develop over the next few days, especially over
waters west of Maui County. Seas should remain just below
advisory level over exposed Kauai waters as a short-period
northwest swell moves through (peaking today through tonight).
Surf along south facing shores will remain up through early next
week due to expected overlapping, long-period south-southwest
swells. The first swell will peak tonight through Friday, likely
reaching advisory level. A High Surf Advisory remains in effect
for south facing shores through Friday. Expect rough conditions
for most south exposures through this period due to a combination
of the onshore winds, swell, and periodic heavy showers moving
through. As this swell slowly eases over the weekend, a fresh,
long-period south-southwest swell will begin to fill in through
the day Sunday. This will peak early next week before easing
through midweek. Ongoing short-period northwest swell will keep
surf along north and west facing shores below advisory thresholds.
This swell will linger into Friday, then ease through the
weekend. 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 Friday evening for Niihau, Kauai, Oahu,
Molokai, and Lanai.
High Surf Advisory until 6 PM HST Friday for south facing shores
of all islands.
Small Craft Advisory until 6 PM HST Friday for Big Island
Windward Waters-Big Island Leeward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Walsh
MARINE...Powell
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
053
FXHW60 PHFO 170202
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
402 PM HST Thu May 16 2024
.SYNOPSIS...
A kona low north of the state will continue drawing unstable
tropical moisture northward over the islands over the next couple
of days. Bands of showers producing moderate to heavy rain and
isolated thunderstorms will move over the central and western
islands tonight through at least Friday. The kona low will begin
to drift away from the state this weekend with improving trends
over the eastern islands, while enhanced rainfall will linger over
the western end of the state into Sunday. All islands will see an
improvement in weather conditions next week as trade winds
gradually return.
&&
.DISCUSSION...
A kona low currently centered roughly 650 nautical miles north-
northwest of Kauai and will continue to impact the state over the
next couple of days. Latest surface analysis this afternoon
continues to show a dying stationary front stretching from the
kona low into the Kauai Channel near the North Shore of Oahu. An
additional surface trough is located roughly 50 miles north of
Kauai.
Surface observations ahead of the frontal boundary show southerly
kona winds that are bringing unstable, deep tropical moisture
from the tropics over the islands. CIMMS MIMIC Layer precipitable
water continues to show PW values from roughly 1.5 to 2.20 inches
across the state. Latest radar imagery this afternoon shows that
light to moderate rain, with occasional pockets of heavier
rain, are moving across the smaller islands, especially Oahu
where surface convergence is maximized. Throughout the day, radar
trends and observed rainfall amounts have fallen a bit short of
what hi-res model guidance would have suggested, limiting overall
flooding impacts to nuisance ponding on roadways, ponding in low-
lying areas, and brief rises in stream levels. For the Big
Island, afternoon convection has produced isolated heavy rain over
the upper North Hilo and South Hilo Districts as well.
With that said, we are still expecting additional impacts tonight
through at least late Friday. Overnight, we are expecting the axis
of heaviest rainfall potential to shift westward back over Oahu
and eventually to focus on Kauai on Friday. As showers train over
already saturated areas, flash flooding will be possible and
streams will become more responsive to downpours. Based on the
latest guidance, the Flood Watch has been cancelled for the
islands of Kahoolawe and Maui since the main impacts are expected
farther west. Therefore, a Flood Watch remains in effect for
Niihau, Kauai, Oahu, Molokai, and Lanai.
Although enhanced rainfall is expected to linger near the western
end of the state throughout the weekend, drier and more stable
east to southeasterly winds will begin to move into the region as
a ridge builds from the east and the kona low drifts northward.
Easterly trade winds will begin to return by the middle of next
week.
&&
.AVIATION...
A strong kona low NNW of Kauai is pulling tropical moisture out
of the south across the state. This will keep the the islands in
an active weather pattern through the remainder of the week into
the weekend. Moderate to heavy SHRA and possible TS are expected
over the western side of the state today and tomorrow. On the Big
Island, SHRA is expected this afternoon into the evening hours.
IFR/MVFR conds expected across the smaller islands especially in
heavier SHRA/TS.
AIRMET Sierra is in effect for for mtn obsc for Kauai, Oahu,
Molokai, Lanai, Maui and windward Big Island.
AIRMET Sierra for IFR conds over Kauai, Oahu, Molokai and Lanai.
AIRMET Tango is in effect for turb blw 120 N thru E of the Big
Island.
AIRMET Zulu is in effect for light rime icing from Kauai to Maui
in layer 140-FL250.
&&
.MARINE...
Strong south to southeast winds associated with a kona low north-
northwest of the state will persist through Friday for most
waters. A shift out of the east to southeast is expected over the
weekend through early next week as the low lifts northward and
away from the area. A Small Craft Advisory remains in effect for
windward and leeward Big Island waters (Hamakua Coast and waters
near South Point). Expect rough seas in heavy showers or
thunderstorms that develop over the next few days, especially over
waters west of Maui County. Seas should remain just below
advisory level over exposed Kauai waters as a short-period
northwest swell moves through (peaking today through tonight).
Surf along south facing shores will remain up through early next
week due to expected overlapping, long-period south-southwest
swells. The first swell will peak tonight through Friday, likely
reaching advisory level. A High Surf Advisory remains in effect
for south facing shores through Friday. Expect rough conditions
for most south exposures through this period due to a combination
of the onshore winds, swell, and periodic heavy showers moving
through. As this swell slowly eases over the weekend, a fresh,
long-period south-southwest swell will begin to fill in through
the day Sunday. This will peak early next week before easing
through midweek. Ongoing short-period northwest swell will keep
surf along north and west facing shores below advisory thresholds.
This swell will linger into Friday, then ease through the
weekend. 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 Friday evening for Niihau, Kauai, Oahu,
Molokai, and Lanai.
High Surf Advisory until 6 PM HST Friday for south facing shores
of all islands.
Small Craft Advisory until 6 PM HST Friday for Big Island
Windward Waters-Big Island Leeward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Walsh
MARINE...Powell
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office