706 
FXHW60 PHFO 071353
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
353 AM HST Sun Apr 7 2024

.SYNOPSIS...
Surface high pressure far north of the state is weakening as it
moves east. This will result in the gradual weakening of trade 
winds through Tuesday. Periodic bands of showers moving in from 
the east will focus rainfall over windward exposures, with 
occasional showers passing into leeward areas. Low pressure is 
expected to develop several hundred miles northwest of the state 
Wednesday. This scenario would veer easterlies more southerly and 
increase humidity. The potential exists for more numerous showers 
and isolated thunderstorms that could produce locally heavy rain 
Thursday and Friday over the western half of the state.


&&

.DISCUSSION...
The large surface high positioned about 900 miles north northeast
of Oahu is beginning to drift east southeast and weaken. The
result has been the subtle weakening of our local winds. Overnight 
winds over exposed terrain prone to higher gusts on both Big 
Island and Maui County have been steadily falling into the 30 to 
40 mph range. Therefore, the Wind Advisory for the northern and 
southeastern regions of Big Island and windward areas of Maui 
County has been cancelled. The subtropical jet streaming across 
the state is maintaining a near 10 kft inversion and likely 
creating enough upper level diffluence to generate some lift 
within a fairly saturated boundary layer. Diffuse bands of 
moisture are producing scattered offshore showers that are filling
in across the smaller islands this morning. A slug of higher mid 
level moisture just east of the island chain will likely have 
windward Big Island getting into the higher rainfall action later 
this morning. Gusty trades will periodically carry showers over 
into the leeward areas of most islands. 

A near-stationary mid and upper level low northwest of the region
and its associated trough extending north of the islands will 
continue to maintain an elevated subsidence inversion the next 
few days. The region will remain under these relatively lower mid 
to upper level heights through Tuesday. Periodic pockets of 
higher moisture and subsequent showers will ride in on the lower 
level easterly steering flow. The jet passing overhead, in 
addition to this deeper mid layer moisture, will help support 
early week partly to mostly cloudy skies for most lower
elevations, mainly overcast and wetter windward/upslope higher 
terrain conditions. While not receiving as much accumulated rain, 
downstream leeward locations will experience frequent downpours 
from windward spillover showers. Organized showers may produce 
brief periods of strong gusty conditions with their passage.
 
As the upper low drifts east and in the vicinity of Kauai late 
Monday or early Tuesday, there will be increased chances for 
heavier rain or isolated offshore thunderstorms north of the 
island. Trades will decline further Tuesday as low pressure at 
the surface and aloft starts to develop several hundred miles 
northwest of Kauai. Trades will begin to veer southeasterly 
Tuesday night and decreasing stability could trigger some heavier
showers over more windward slopes. Upper-level troughing 
northwest of the state will dig southeastward toward the islands 
going into Wednesday. Forecast confidence is slightly increasing 
beyond Wednesday as both ensemble and deterministic model 
solutions are in better agreement on the development and 
evolution of a late week deep cut off low northwest of the state. 
Late week winds will veer southerly and tap into more moisture- 
rich equatorial air. Thursday and Friday's rain may become 
locally heavy, especially across the western half of the state, as
southern convergence bands draw up a 50% higher precipitable 
water air mass (than a couple of days prior). 


&&

.AVIATION...
Strong high pressure north of the state will drive breezy trade 
winds today and tonight. Bands of low clouds and showers will 
bring widespread MVFR cigs/vsbys to windward areas of the smaller 
islands through late this morning, with improving conditions
expected this afternoon. Widespread MVFR conditions will develop
over windward Big Island later this morning and hold on through
the remainder of the day before improving tonight. Showers will 
reach leeward sections of the smaller islands frequently through
the morning hours, with coverage diminishing this afternoon. Some
brief MVFR conditions will be possible in leeward areas through
the morning hours, but predominantly VFR conditions will prevail.

AIRMET Sierra remains in effect for mountain obscuration over
windward sections of Kauai, Oahu, Molokai and Maui. Little change
is expected through the morning hours, with improvement expected
this afternoon. AIRMET Sierra will likely need to be expanded to 
include the Big Island later this morning.

AIRMET Tango remains in effect for moderate low level turbulence
over and downwind of the terrain of all islands. Little change is
expected during the next 24 hours.


&&

.MARINE...
A strong surface high pressure north of the islands continues to 
drive strong to near gale-force easterly trade winds across the 
coastal waters. This high will weaken as it slowly drifts south 
then east over the next few days. The Gale Warning for the 
typically windier waters of Maui County and around the Big Island 
has been downgraded to a Small Craft Advisory (SCA) as the winds 
begin to taper off. An SCA remains in effect for all coastal 
waters through the day due to a combination of strong winds and 
seas. As winds and seas slowly decline through the day, the SCA
may be pulled back to typical windy waters around Maui County and
the Big Island tonight. A surface trough will set up west of the 
state around Tuesday with winds weakening and veering 
southeasterly across the islands, leading to southeast veering and
lighter winds Tuesday and Wednesday. The SCA will likely drop for
all zones coinciding with the declining winds and seas.

East facing shores will continue to see elevated short period
rough surf as the strong trade wind generated seas continue to
impact the islands. A High Surf Advisory (HSA) has been extended
till 6 pm today for all exposed east facing shores. As trade 
winds gradually ease near and upstream of the state, the rough 
surf along east and exposed north facing shores will gradually 
decline.

Surf along north facing shores will remain elevated due to areas 
exposed to the east wrap, as well as small northerly reinforcements.
A small medium period northwest swell is expected to fill in 
Monday night and hold through Wednesday. The second half of the 
week guidance suggests a low developing north of the state that 
could aim a moderate short to medium period north- northwest swell
reaching the islands by Thursday night and Friday.

For southern shores, small pulses of medium period south-southeast
swell and long period southwest swell will move through over the 
next several days.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening for Olomana-Maui 
Windward West-Kauai East-Kauai South-Koolau Windward-Molokai 
Windward-Molokai Southeast-Windward Haleakala-Big Island 
Southeast-Big Island East-Big Island North.

Small Craft Advisory until 6 PM HST this evening for all 
Hawaiian waters-


&&

$$


DISCUSSION...Blood
AVIATION...Jelsema
MARINE...Shigesato

374 
FXHW60 PHFO 071441
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
353 AM HST Sun Apr 7 2024

.SYNOPSIS...
Surface high pressure far north of the state is weakening as it
moves east. This will result in the gradual weakening of trade 
winds through Tuesday. Periodic bands of showers moving in from 
the east will focus rainfall over windward exposures, with 
occasional showers passing into leeward areas. Low pressure is 
expected to develop several hundred miles northwest of the state 
Wednesday. This scenario would veer easterlies more southerly and 
increase humidity. The potential exists for more numerous showers 
and isolated thunderstorms that could produce locally heavy rain 
Thursday and Friday over the western half of the state.


&&

.DISCUSSION...
The large surface high positioned about 900 miles north northeast
of Oahu is beginning to drift east southeast and weaken. The
result has been the subtle weakening of our local winds. Overnight 
wind gusts over exposed terrain prone to higher gusts on both Big 
Island and around Maui County have been steadily falling into the 20 
to 30 mph range. Therefore, the Wind Advisory for the northern and 
southeastern regions of Big Island and windward areas of Maui County 
has been cancelled. The subtropical jet streaming across the state 
is maintaining a near 10 kft inversion and likely creating enough 
upper level diffluence to generate some lift within a fairly 
saturated boundary layer. Diffuse bands of moisture are producing 
scattered offshore showers that are filling in across the smaller 
islands this morning. A slug of higher mid level moisture just east 
of the island chain will likely have windward Big Island getting 
into the higher rainfall action later this morning. Gusty trades 
will periodically carry showers over into the leeward areas of most 
islands. 

A near-stationary mid and upper level low northwest of the region
and its associated trough extending north of the islands will 
continue to maintain an elevated subsidence inversion the next 
few days. The region will remain under these relatively lower mid 
to upper level heights through Tuesday. Periodic pockets of 
higher moisture and subsequent showers will ride in on the lower 
level easterly steering flow. The jet passing overhead, in 
addition to this deeper mid layer moisture, will help support 
early week partly to mostly cloudy skies for most lower
elevations, mainly overcast and wetter windward/upslope higher 
terrain conditions. While not receiving as much accumulated rain, 
downstream leeward locations will experience frequent downpours 
from windward spillover showers. Organized showers may produce 
brief periods of strong gusty conditions with their passage.
 
As the upper low drifts east and in the vicinity of Kauai late 
Monday or early Tuesday, there will be increased chances for 
heavier rain or isolated offshore thunderstorms north of the 
island. Trades will decline further Tuesday as low pressure at 
the surface and aloft starts to develop several hundred miles 
northwest of Kauai. Trades will begin to veer southeasterly 
Tuesday night and decreasing stability could trigger some heavier
showers over more windward slopes. Upper-level troughing 
northwest of the state will dig southeastward toward the islands 
going into Wednesday. Forecast confidence is slightly increasing 
beyond Wednesday as both ensemble and deterministic model 
solutions are in better agreement on the development and 
evolution of a late week deep cut off low northwest of the state. 
Late week winds will veer southerly and tap into more moisture- 
rich equatorial air. Thursday and Friday's rain may become 
locally heavy, especially across the western half of the state, as
southern convergence bands draw up a 50% higher precipitable 
water air mass (than a couple of days prior). 


&&

.AVIATION...
Strong high pressure north of the state will drive breezy trade 
winds today and tonight. Bands of low clouds and showers will 
bring widespread MVFR cigs/vsbys to windward areas of the smaller 
islands through late this morning, with improving conditions
expected this afternoon. Widespread MVFR conditions will develop
over windward Big Island later this morning and hold on through
the remainder of the day before improving tonight. Showers will 
reach leeward sections of the smaller islands frequently through
the morning hours, with coverage diminishing this afternoon. Some
brief MVFR conditions will be possible in leeward areas through
the morning hours, but predominantly VFR conditions will prevail.

AIRMET Sierra remains in effect for mountain obscuration over
windward sections of Kauai, Oahu, Molokai and Maui. Little change
is expected through the morning hours, with improvement expected
this afternoon. AIRMET Sierra will likely need to be expanded to 
include the Big Island later this morning.

AIRMET Tango remains in effect for moderate low level turbulence
over and downwind of the terrain of all islands. Little change is
expected during the next 24 hours.


&&

.MARINE...
A strong surface high pressure north of the islands continues to 
drive strong to near gale-force easterly trade winds across the 
coastal waters. This high will weaken as it slowly drifts south 
then east over the next few days. The Gale Warning for the 
typically windier waters of Maui County and around the Big Island 
has been downgraded to a Small Craft Advisory (SCA) as the winds 
begin to taper off. An SCA remains in effect for all coastal 
waters through the day due to a combination of strong winds and 
seas. As winds and seas slowly decline through the day, the SCA
may be pulled back to typical windy waters around Maui County and
the Big Island tonight. A surface trough will set up west of the 
state around Tuesday with winds weakening and veering 
southeasterly across the islands, leading to southeast veering and
lighter winds Tuesday and Wednesday. The SCA will likely drop for
all zones coinciding with the declining winds and seas.

East facing shores will continue to see elevated short period
rough surf as the strong trade wind generated seas continue to
impact the islands. A High Surf Advisory (HSA) has been extended
till 6 pm today for all exposed east facing shores. As trade 
winds gradually ease near and upstream of the state, the rough 
surf along east and exposed north facing shores will gradually 
decline.

Surf along north facing shores will remain elevated due to areas 
exposed to the east wrap, as well as small northerly reinforcements.
A small medium period northwest swell is expected to fill in 
Monday night and hold through Wednesday. The second half of the 
week guidance suggests a low developing north of the state that 
could aim a moderate short to medium period north- northwest swell
reaching the islands by Thursday night and Friday.

For southern shores, small pulses of medium period south-southeast
swell and long period southwest swell will move through over the 
next several days.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening for Olomana-Maui 
Windward West-Kauai East-Kauai South-Koolau Windward-Molokai 
Windward-Molokai Southeast-Windward Haleakala-Big Island 
Southeast-Big Island East-Big Island North.

Small Craft Advisory until 6 PM HST this evening for all 
Hawaiian waters-


&&

$$


DISCUSSION...Blood
AVIATION...Jelsema
MARINE...Shigesato