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Hawaiian Islands Synoptic Discussion and Guidance
978
FXHW60 PHFO 120148
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
348 PM HST Wed Mar 11 2026
.SYNOPSIS...
A powerful kona storm will impact the state through this weekend
resulting in potential flash flooding, damaging winds, and strong
to severe thunderstorms. Impacts will generally be felt over the
western end of the state first and then spread east with time. The
peak of this event is forecast to be Friday and Saturday.
&&
.DISCUSSION...
Tonight. NE-SW oriented moisture axis in place over the islands
supports ongoing shower activity as the mid and upper levels slowly
destabilize. These showers are anchored along a corridor of
weakly confluent SW flow and will evolve eastward through tonight
through Maui County tonight. Paltry convergence is likely to limit
potential for organization and meaningful heavy rain tonight.
Thursday. The next wave of showers in the sequence is beginning to
materialize along the same moisture axis well south of Kauai today.
Stellar left exit jet support and steady dynamic forcing aloft will
allow this developing band of showers to intensify as it reaches
Kauai and possibly Oahu early Thursday. Lapse rates on the order
of 7C/km and 500mb temperatures around -13C will favor embedded
thunderstorms. Despite the increasingly favorable thermodynamic
environment, low-level convergence will be lacking for much of the
day Thursday. This will likely lead to poorly organized batches of
heavy rainfall and/or thunderstorms through at least the first
half of the day. Additionally, the left exit circulation and
local pressure falls will force winds to steadily ramp up during
Thursday with 850mb winds reaching 35 kts by Thursday evening and
sustained southerlies in the vicinity of Kauai around 20-25kts.
Strong southerly moisture transport may favor fairly widespread
showers by afternoon, but gradually strengthening surface
convergence will increasingly place the focus on the developing
heavy rain band over Kauai. An increasingly organized band of
heavy rain and thunderstorms is expected to be taking shape over
Kauai no later than Thursday evening.
Thursday night through Saturday. This represents the period of
greatest concern and the potential timing for considerable impacts
to life and property. 850mb low-level jet further ramps up to nearly
50 kts on Thursday as sustained southerlies settle around 25 kts. As
usual, downsloping potential exists but is uncertain. Suspect power
outages and downed trees will be common by late Thursday night into
early Friday, particularly where soil is water logged. Of note, a
strong punch of mid level dry air and subsidence impinges on Kauai
and Oahu during the day Saturday when the wind field still remains
quite strong. This may represent even greater potential for
downsloping winds to develop. Therefore, a High Wind Watch has
been issued for the lower elevations beginning Thursday night and
continuing through Saturday night for Kauai through Maui. An HWW
for the Big Island has likewise been issued with a start time of
early Friday. This Watch will later be converted to either a Wind
Advisory or a High Wind Warning as downsloping potential becomes
more clear, though the aforementioned dry intrusion increases
confidence that strong downsloping winds will occur if not during
the entire watch period, then at least during the tail end of it
Sat-Sat night.
This period will also be characterized by intense rain rates,
thunderstorms, and the potentially serious flash flooding. The most
intense rainfall will be focused along the rapidly strengthening
frontal zone as it slowly progresses eastward through the state.
This band will develop over Kauai by late Thursday, reach Oahu
during Friday and Maui County late Friday into Friday night. The
heavy rain axis finally reaches the Big Island on Saturday, focusing
heavy rain along leeward areas. Also suspect showers will ramp up
during this time frame over the SE slopes of the Big Island
potentially resulting in several inches of rain in advance of the
heavy rain band. There is also a slight risk for severe
thunderstorms. Wind profiles are largely unidirectional out of the
SW which will favor a primary threat of wind. However, large hail
(1" diameter or greater) is also not out of the question with any
particularly intense thunderstorms. It should be noted that the
heavy rain band is forecast to move slowly but still be rather
progressive in nature. Should it stall over an island, the threat
for severe flooding would drastically increase.
Finally, Big Island and Haleakala Summits will see winds ramp up
Friday into Saturday. Gusts over 100 mph can be expected on the Big
Island with lesser gusts of 80-90 mph developing on Haleakala Summit
by early Saturday. This will coincide with the period of heaviest
precip in these areas. Blizzard conditions are therefore anticipated
on the Big Island Summits. The High Wind Watch and Winter Storm
Watch for the summits remain in effect.
Sunday onward. Moist SW flow potentially favors continuing showers,
though of diminished intensity over Leeward Big Island. The next
round of mid-level height falls approaches during the middle of next
week potentially reactivating the lingering band of moisture over
the islands.
&&
.AVIATION...
Shower activity has become broken this afternoon, with
the expectation that showers will become more isolated for Maui
County and the Big Island this evening, while a more scattered
threat persists for Kauai and Oahu. Most sites currently read VFR
this afternoon, however sites under showers may fall as low as
LIFR at times. Showers are expected to spread eastward during the
day Thursday, with isolated thunderstorms possible, however
confidence remained too low to make mention in the TAFs
themselves.
AIRMET SIERRA remains in effect for mountain obscuration for all
of Kauai, Oahu and Maui Counties, as well as the south and
southeast portions of the Big Island.
AIRMET ZULU remains in effect for light icing from Kauai through
Maui County for FL 130-240.
AIRMET TANGO is in effect for moderate turbulence over Kauai and
Oahu as winds are expected to be breezy out of the south over the
next couple of days.
AIRMET TANGO is also in effect across the state for moderate
turbulence associated with this ongoing Kona low. Upper level
turbulence is generally expected to decrease towards the evening
with the exception of areas with thunderstorms.
&&
.MARINE...
A powerful kona storm will result in heavy rain, thunderstorms,
and rough seas for the islands and adjacent coastal waters
through the rest of this week. Today's scatterometer passes showed
winds have significantly diminished around the Big Island, though
they remain fresh near Kauai. As a result, the Small Craft
Advisory (SCA) has been cancelled. A relative lull in winds is
forecast tonight before strong southerly winds redevelop Thursday
afternoon. Winds are likely to approach, or possibly reach, gale-
force for portions of the area as early as Thursday night or
Friday and last into the weekend in association with a band of
heavy rainfall and thunderstorms pushing eastward across the
forecast area.
A series of small, medium- to long-period west-northwest swells
will bring small surf to north and west facing shores through the
rest of the week. Kauai will block some of this swell energy from
reaching Oahu and Maui, but it will make it into the west facing
shores of the Big Island. The current swell will begin to diminish
late Thursday before the next west-northwest swell builds Friday into
the weekend. Additionally, a small, medium-period north swell
originating from Alaska Peninsula gap winds is expected to arrive
Thursday night and continue into the weekend.
Choppy surf along east-facing shores will continue to trend downward
and remain below seasonal levels as south to southeast winds prevail.
The southerly wind direction will contribute to rough and choppy surf
along south-facing shores, but a bit of a lull can be expected on
Thursday with a brief break in southerly winds before they reintensify
Thursday night. South shore surf will build further Friday into the
weekend, likely reaching advisory levels. Once southerly winds
diminish early next week, a small to moderate, long-period south
swell generated by a gale force low southeast of New Zealand will
arrive along south-facing shores.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday afternoon for Niihau-Kauai Leeward-
Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central
Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West-
Maui Leeward West-Haleakala Summit-Kauai North-Kauai East-Kauai
South-East Honolulu-Honolulu Metro-Ewa Plain-Koolau Windward-
Koolau Leeward-Molokai-Lanai Windward-Lanai Leeward-Lanai South-
Maui Central Valley North-Maui Central Valley South-Windward
Haleakala-Kipahulu-South Maui/Upcountry-South Haleakala.
High Wind Watch from Thursday evening through late Saturday
night for Niihau-Kauai Leeward-Kauai Mountains-Waianae Coast-
Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Lanai
Mauka-Kahoolawe-Maui Windward West-Maui Leeward West-Kauai North-
Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-
Koolau Windward-Koolau Leeward-Molokai-Lanai Windward-Lanai
Leeward-Lanai South-Maui Central Valley North-Maui Central
Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry-
South Haleakala.
High Wind Watch from Thursday evening through Sunday afternoon
for Haleakala Summit-Big Island Summits.
Flood Watch from 6 PM HST this evening through Saturday
afternoon for Kona-Kohala-Big Island Interior-Big Island South-
Big Island Southeast-Big Island East-Big Island North.
High Wind Watch from Friday morning through late Saturday night
for Kona-Kohala-Big Island Interior-Big Island South-Big Island
Southeast-Big Island East-Big Island North.
Winter Storm Watch from Thursday evening through Saturday
afternoon for Big Island Summits.
Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-
Kauai Channel-Big Island Windward Waters-Big Island Leeward
Waters.
&&
$$
DISCUSSION...JVC
AVIATION...Evans
MARINE...CQ
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
978
FXHW60 PHFO 120148
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
348 PM HST Wed Mar 11 2026
.SYNOPSIS...
A powerful kona storm will impact the state through this weekend
resulting in potential flash flooding, damaging winds, and strong
to severe thunderstorms. Impacts will generally be felt over the
western end of the state first and then spread east with time. The
peak of this event is forecast to be Friday and Saturday.
&&
.DISCUSSION...
Tonight. NE-SW oriented moisture axis in place over the islands
supports ongoing shower activity as the mid and upper levels slowly
destabilize. These showers are anchored along a corridor of
weakly confluent SW flow and will evolve eastward through tonight
through Maui County tonight. Paltry convergence is likely to limit
potential for organization and meaningful heavy rain tonight.
Thursday. The next wave of showers in the sequence is beginning to
materialize along the same moisture axis well south of Kauai today.
Stellar left exit jet support and steady dynamic forcing aloft will
allow this developing band of showers to intensify as it reaches
Kauai and possibly Oahu early Thursday. Lapse rates on the order
of 7C/km and 500mb temperatures around -13C will favor embedded
thunderstorms. Despite the increasingly favorable thermodynamic
environment, low-level convergence will be lacking for much of the
day Thursday. This will likely lead to poorly organized batches of
heavy rainfall and/or thunderstorms through at least the first
half of the day. Additionally, the left exit circulation and
local pressure falls will force winds to steadily ramp up during
Thursday with 850mb winds reaching 35 kts by Thursday evening and
sustained southerlies in the vicinity of Kauai around 20-25kts.
Strong southerly moisture transport may favor fairly widespread
showers by afternoon, but gradually strengthening surface
convergence will increasingly place the focus on the developing
heavy rain band over Kauai. An increasingly organized band of
heavy rain and thunderstorms is expected to be taking shape over
Kauai no later than Thursday evening.
Thursday night through Saturday. This represents the period of
greatest concern and the potential timing for considerable impacts
to life and property. 850mb low-level jet further ramps up to nearly
50 kts on Thursday as sustained southerlies settle around 25 kts. As
usual, downsloping potential exists but is uncertain. Suspect power
outages and downed trees will be common by late Thursday night into
early Friday, particularly where soil is water logged. Of note, a
strong punch of mid level dry air and subsidence impinges on Kauai
and Oahu during the day Saturday when the wind field still remains
quite strong. This may represent even greater potential for
downsloping winds to develop. Therefore, a High Wind Watch has
been issued for the lower elevations beginning Thursday night and
continuing through Saturday night for Kauai through Maui. An HWW
for the Big Island has likewise been issued with a start time of
early Friday. This Watch will later be converted to either a Wind
Advisory or a High Wind Warning as downsloping potential becomes
more clear, though the aforementioned dry intrusion increases
confidence that strong downsloping winds will occur if not during
the entire watch period, then at least during the tail end of it
Sat-Sat night.
This period will also be characterized by intense rain rates,
thunderstorms, and the potentially serious flash flooding. The most
intense rainfall will be focused along the rapidly strengthening
frontal zone as it slowly progresses eastward through the state.
This band will develop over Kauai by late Thursday, reach Oahu
during Friday and Maui County late Friday into Friday night. The
heavy rain axis finally reaches the Big Island on Saturday, focusing
heavy rain along leeward areas. Also suspect showers will ramp up
during this time frame over the SE slopes of the Big Island
potentially resulting in several inches of rain in advance of the
heavy rain band. There is also a slight risk for severe
thunderstorms. Wind profiles are largely unidirectional out of the
SW which will favor a primary threat of wind. However, large hail
(1" diameter or greater) is also not out of the question with any
particularly intense thunderstorms. It should be noted that the
heavy rain band is forecast to move slowly but still be rather
progressive in nature. Should it stall over an island, the threat
for severe flooding would drastically increase.
Finally, Big Island and Haleakala Summits will see winds ramp up
Friday into Saturday. Gusts over 100 mph can be expected on the Big
Island with lesser gusts of 80-90 mph developing on Haleakala Summit
by early Saturday. This will coincide with the period of heaviest
precip in these areas. Blizzard conditions are therefore anticipated
on the Big Island Summits. The High Wind Watch and Winter Storm
Watch for the summits remain in effect.
Sunday onward. Moist SW flow potentially favors continuing showers,
though of diminished intensity over Leeward Big Island. The next
round of mid-level height falls approaches during the middle of next
week potentially reactivating the lingering band of moisture over
the islands.
&&
.AVIATION...
Shower activity has become broken this afternoon, with
the expectation that showers will become more isolated for Maui
County and the Big Island this evening, while a more scattered
threat persists for Kauai and Oahu. Most sites currently read VFR
this afternoon, however sites under showers may fall as low as
LIFR at times. Showers are expected to spread eastward during the
day Thursday, with isolated thunderstorms possible, however
confidence remained too low to make mention in the TAFs
themselves.
AIRMET SIERRA remains in effect for mountain obscuration for all
of Kauai, Oahu and Maui Counties, as well as the south and
southeast portions of the Big Island.
AIRMET ZULU remains in effect for light icing from Kauai through
Maui County for FL 130-240.
AIRMET TANGO is in effect for moderate turbulence over Kauai and
Oahu as winds are expected to be breezy out of the south over the
next couple of days.
AIRMET TANGO is also in effect across the state for moderate
turbulence associated with this ongoing Kona low. Upper level
turbulence is generally expected to decrease towards the evening
with the exception of areas with thunderstorms.
&&
.MARINE...
A powerful kona storm will result in heavy rain, thunderstorms,
and rough seas for the islands and adjacent coastal waters
through the rest of this week. Today's scatterometer passes showed
winds have significantly diminished around the Big Island, though
they remain fresh near Kauai. As a result, the Small Craft
Advisory (SCA) has been cancelled. A relative lull in winds is
forecast tonight before strong southerly winds redevelop Thursday
afternoon. Winds are likely to approach, or possibly reach, gale-
force for portions of the area as early as Thursday night or
Friday and last into the weekend in association with a band of
heavy rainfall and thunderstorms pushing eastward across the
forecast area.
A series of small, medium- to long-period west-northwest swells
will bring small surf to north and west facing shores through the
rest of the week. Kauai will block some of this swell energy from
reaching Oahu and Maui, but it will make it into the west facing
shores of the Big Island. The current swell will begin to diminish
late Thursday before the next west-northwest swell builds Friday into
the weekend. Additionally, a small, medium-period north swell
originating from Alaska Peninsula gap winds is expected to arrive
Thursday night and continue into the weekend.
Choppy surf along east-facing shores will continue to trend downward
and remain below seasonal levels as south to southeast winds prevail.
The southerly wind direction will contribute to rough and choppy surf
along south-facing shores, but a bit of a lull can be expected on
Thursday with a brief break in southerly winds before they reintensify
Thursday night. South shore surf will build further Friday into the
weekend, likely reaching advisory levels. Once southerly winds
diminish early next week, a small to moderate, long-period south
swell generated by a gale force low southeast of New Zealand will
arrive along south-facing shores.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday afternoon for Niihau-Kauai Leeward-
Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central
Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West-
Maui Leeward West-Haleakala Summit-Kauai North-Kauai East-Kauai
South-East Honolulu-Honolulu Metro-Ewa Plain-Koolau Windward-
Koolau Leeward-Molokai-Lanai Windward-Lanai Leeward-Lanai South-
Maui Central Valley North-Maui Central Valley South-Windward
Haleakala-Kipahulu-South Maui/Upcountry-South Haleakala.
High Wind Watch from Thursday evening through late Saturday
night for Niihau-Kauai Leeward-Kauai Mountains-Waianae Coast-
Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Lanai
Mauka-Kahoolawe-Maui Windward West-Maui Leeward West-Kauai North-
Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-
Koolau Windward-Koolau Leeward-Molokai-Lanai Windward-Lanai
Leeward-Lanai South-Maui Central Valley North-Maui Central
Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry-
South Haleakala.
High Wind Watch from Thursday evening through Sunday afternoon
for Haleakala Summit-Big Island Summits.
Flood Watch from 6 PM HST this evening through Saturday
afternoon for Kona-Kohala-Big Island Interior-Big Island South-
Big Island Southeast-Big Island East-Big Island North.
High Wind Watch from Friday morning through late Saturday night
for Kona-Kohala-Big Island Interior-Big Island South-Big Island
Southeast-Big Island East-Big Island North.
Winter Storm Watch from Thursday evening through Saturday
afternoon for Big Island Summits.
Small Craft Advisory until 6 PM HST this evening for Kauai
Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-
Kauai Channel-Big Island Windward Waters-Big Island Leeward
Waters.
&&
$$
DISCUSSION...JVC
AVIATION...Evans
MARINE...CQ
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office