NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
496
FXHW60 PHFO 060643
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
843 PM HST Mon Oct 5 2026
.SYNOPSIS...
Moderate to locally breezy trades will continue to bring isolated
to scattered showers to windward and mauka areas through this
evening. Winds will begin to ease tonight, then turn out of the
south by midweek as an area of low pressure develops to the north
of the state. Rain chances and the potential for heavy rain will
increase during the second half of the week.
&&
.SHORT TERM UPDATE...
No changes were made to the forecast. In the short term, isolated
to scattered light showers will focus along windward and mauka
slopes overnight. Clouds and showers built upslope from Kailua-
Kona to South Point and up to Volcano is starting to trend down
and push offshore as land breezes develop. Remainder of forecast
remains on track with moderate to locally breezy trades easing
overnight and Tuesday allowing a hybrid pattern of light trades
and sea breezes to develop in the afternoon.
&&
.PREV DISCUSSION...
Issued at 358 PM HST Mon Oct 5 2026
Current radar and satellite imagery show isolated to scattered
showers moving into windward and mauka areas of the state on the
moderate to locally breezy trades this afternoon, along with
clouds and showers developing along the kona slopes of the Big
Island from Kailua-Kona to South Point and up to Volcano due to
daytime heating.
The high driving our trades to the northeast of the state will
weaken and shift further northeast as deep troughing develops
across the region north of the state over the next couple of
days. This will weaken the trade wind flow late tonight into
Tuesday, allowing for a hybrid lighter trade wind and land/sea
breeze pattern to develop with limited showers favoring windward
and mauka areas overnight, then daytime heating will induce clouds
and a few showers over leeward areas Tuesday afternoon.
Model guidance continues to indicate that the trough to the north
will deepen and form a broad cutoff low both aloft and at the
surface by late Wednesday into Thursday, causing the low level
flow to veer out of the south across the state. With the
increasing instability due to the nearby low and deep tropical
moisture being advected northward in the southerly flow, the
potential for heavy rain will increase beginning Wednesday and
persist through at least Friday. In this flow, the heavy showers
will likely favor south-facing portions of each island.
Beyond Friday, forecast confidence decreases significantly as
the global deterministic model solutions diverge. However, the
ensembles lean toward bringing trades back on Saturday into
Sunday, so have nudged the forecast in that direction for now.
&&
.AVIATION...
Moderate to locally breezy trade winds continue through tonight,
but weaken Tuesday due to a nearby surface trough. This will
cause a hybrid light trade wind and sea breeze pattern on Tuesday.
Terrain sheltered areas will be more likely to see afternoon
cloud and shower development as a result. Brief and isolated
shower activity is expected over windward and mountain areas. MVFR
conditions will occur within showers, while VFR prevails
elsewhere.
AIRMET Sierra is in effect for mountain obscuration for portions
of the Big Island this evening, though conditions should
generally improve by early Tuesday morning.
&&
.MARINE...
Issued at 358 PM HST Mon Oct 5 2026
High pressure centered far northeast of Hawaii will drive
moderate to fresh trade winds tonight. Winds are in the process of
weakening as a low pressure system dig southward towards the
state, therefore, the Small Craft Advisory has been cancelled for
all waters and should remain so through the rest of the week. The
low will stall north of the islands and draw moisture out of the
tropics and over the area through the second half of the week, so
expect an increase in showers.
A long-period south swell will increase to slightly above
seasonal averages through Wednesday. Surf is then forecast to
drop to near or slightly below average for the rest of the week,
maintained by a mix of new, small south swells.
A long-period northwest swell will arrive on Tuesday that will
continue through the end of the week even as swell energy becomes
shorter period as it is reinforced by a low to the north-
northwest of the Hawaiian Islands. Surf along east facing shores
will diminish tonight through the rest of the week as winds
weaken.
A small, long-period west swell originating from Typhoon Choi-wan
is forecast to reach the islands Thursday into the weekend, which may
produce moderate surf for west-facing shores.
&&
.FIRE WEATHER...
Issued at 358 PM HST Mon Oct 5 2026
Moderate to locally breezy trades will gradually ease overnight
into Tuesday with RH values just above the critical threshold for
fire weather during the afternoon hours. Fire weather risk then
diminishes through the remainder of the week as moisture
increases, winds decrease, and showers increase in coverage. The
inversion should range from 6 kft to 8 kft through Tuesday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM UPDATE...ALMANZA
DISCUSSION...Farris
AVIATION...Vaughan
MARINE...Foster
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
496
FXHW60 PHFO 060643
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
843 PM HST Mon Oct 5 2026
.SYNOPSIS...
Moderate to locally breezy trades will continue to bring isolated
to scattered showers to windward and mauka areas through this
evening. Winds will begin to ease tonight, then turn out of the
south by midweek as an area of low pressure develops to the north
of the state. Rain chances and the potential for heavy rain will
increase during the second half of the week.
&&
.SHORT TERM UPDATE...
No changes were made to the forecast. In the short term, isolated
to scattered light showers will focus along windward and mauka
slopes overnight. Clouds and showers built upslope from Kailua-
Kona to South Point and up to Volcano is starting to trend down
and push offshore as land breezes develop. Remainder of forecast
remains on track with moderate to locally breezy trades easing
overnight and Tuesday allowing a hybrid pattern of light trades
and sea breezes to develop in the afternoon.
&&
.PREV DISCUSSION...
Issued at 358 PM HST Mon Oct 5 2026
Current radar and satellite imagery show isolated to scattered
showers moving into windward and mauka areas of the state on the
moderate to locally breezy trades this afternoon, along with
clouds and showers developing along the kona slopes of the Big
Island from Kailua-Kona to South Point and up to Volcano due to
daytime heating.
The high driving our trades to the northeast of the state will
weaken and shift further northeast as deep troughing develops
across the region north of the state over the next couple of
days. This will weaken the trade wind flow late tonight into
Tuesday, allowing for a hybrid lighter trade wind and land/sea
breeze pattern to develop with limited showers favoring windward
and mauka areas overnight, then daytime heating will induce clouds
and a few showers over leeward areas Tuesday afternoon.
Model guidance continues to indicate that the trough to the north
will deepen and form a broad cutoff low both aloft and at the
surface by late Wednesday into Thursday, causing the low level
flow to veer out of the south across the state. With the
increasing instability due to the nearby low and deep tropical
moisture being advected northward in the southerly flow, the
potential for heavy rain will increase beginning Wednesday and
persist through at least Friday. In this flow, the heavy showers
will likely favor south-facing portions of each island.
Beyond Friday, forecast confidence decreases significantly as
the global deterministic model solutions diverge. However, the
ensembles lean toward bringing trades back on Saturday into
Sunday, so have nudged the forecast in that direction for now.
&&
.AVIATION...
Moderate to locally breezy trade winds continue through tonight,
but weaken Tuesday due to a nearby surface trough. This will
cause a hybrid light trade wind and sea breeze pattern on Tuesday.
Terrain sheltered areas will be more likely to see afternoon
cloud and shower development as a result. Brief and isolated
shower activity is expected over windward and mountain areas. MVFR
conditions will occur within showers, while VFR prevails
elsewhere.
AIRMET Sierra is in effect for mountain obscuration for portions
of the Big Island this evening, though conditions should
generally improve by early Tuesday morning.
&&
.MARINE...
Issued at 358 PM HST Mon Oct 5 2026
High pressure centered far northeast of Hawaii will drive
moderate to fresh trade winds tonight. Winds are in the process of
weakening as a low pressure system dig southward towards the
state, therefore, the Small Craft Advisory has been cancelled for
all waters and should remain so through the rest of the week. The
low will stall north of the islands and draw moisture out of the
tropics and over the area through the second half of the week, so
expect an increase in showers.
A long-period south swell will increase to slightly above
seasonal averages through Wednesday. Surf is then forecast to
drop to near or slightly below average for the rest of the week,
maintained by a mix of new, small south swells.
A long-period northwest swell will arrive on Tuesday that will
continue through the end of the week even as swell energy becomes
shorter period as it is reinforced by a low to the north-
northwest of the Hawaiian Islands. Surf along east facing shores
will diminish tonight through the rest of the week as winds
weaken.
A small, long-period west swell originating from Typhoon Choi-wan
is forecast to reach the islands Thursday into the weekend, which may
produce moderate surf for west-facing shores.
&&
.FIRE WEATHER...
Issued at 358 PM HST Mon Oct 5 2026
Moderate to locally breezy trades will gradually ease overnight
into Tuesday with RH values just above the critical threshold for
fire weather during the afternoon hours. Fire weather risk then
diminishes through the remainder of the week as moisture
increases, winds decrease, and showers increase in coverage. The
inversion should range from 6 kft to 8 kft through Tuesday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM UPDATE...ALMANZA
DISCUSSION...Farris
AVIATION...Vaughan
MARINE...Foster
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office