NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
438
FXHW60 PHFO 140115
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
315 PM HST Sat Dec 13 2025
.SYNOPSIS...
An approaching cold front will being enhanced showers and isolated
thunderstorms to the western end of the state through Monday
night. Unsettled wet conditions continue through most of next week
as another front approaches from the northwest, then stalls across
the western half of the state.
&&
.DISCUSSION...
Satellite imagery and the latest surface analysis depicts a cold
front approximately 100 miles northwest of Kauai this afternoon.
Radar imagery shows scattered showers across the leeward Kauai and
Oahu waters moving northeast, but generally remaining offshore.
Southerly winds ahead of the front continue across the state, with
broken to overcast skies over leeward portions of the smaller
islands. The forecast remains on track, and continues to show the
potential for heavy rain and isolated thunderstorms capable of
producing flash flooding across portions of Kauai County and Oahu.
A Flood Watch remains in effect for Niihau, Kauai, and Oahu from
midnight tonight through 6 AM Tuesday morning.
The latest hi-res guidance shows the front reaching Kauai around
midnight tonight, the moving eastward and reaching Oahu around
daybreak on Sunday. The front looks to then briefly stall over
East Oahu Sunday afternoon and evening, before retrograding west
and stalling out in the vicinity of Kauai or Oahu Sunday night
into Monday. There remains good agreement with the evolution of
the upper level support associated with the system as a strong
100+ kt southwesterly jet helps to deepen the front and provide a
narrow corridor of strong uplift. This in turn will result in a
mature jet-front system that will support the development of a
band of heavy rain and isolated thunderstorms. There still remains
some uncertainty where this band of heavy rain will eventually
settle Sunday night into Monday, but the western half of the
state could see anywhere from 1.5 to 3 inches between now and
Monday night, with locally higher amounts possible.
The upper level support is expected to lift north on Tuesday and
bring the surface low with it. The surface front will also lift
and weaken, although lingering moisture will remain in the area
keeping some showers around the area on Tuesday. Another surface
low looks to develop near the dateline on Monday, then move east
through late next week. Guidance continues to show a front
approaching the islands from the northwest mid to late next week,
with the front elongating and stalling over the western half of
the state by late next week. There is still some uncertainty with
how strong this front will be, but expect additional showers and
unsettled weather continue through the rest of the week.
&&
.AVIATION...
Southerly winds have increased this afternoon. Expect elevated
and gusty winds to continue especially across the western half of
the state ahead of a front that is approaching Kauai. This front
will bring low cigs, SHRA and a few tstms. IFR/MVFR conds possible
across the western end, while a few eastern end sites will remain
VFR.
AIRMET Sierra is in effect for mtn obsc for Kauai and Oahu. As
conds deteriorate this may become an IFR AIRMET.
&&
.MARINE...
An approaching front will reach of Kauai late this evening
potentially advancing as far east as Oahu by early Sunday. The
Small Craft Advisory for strong SW winds in advance of the front
has been extended until Monday morning due elevated seas poised to
arrive during Sunday morning. Winds rapidly diminish in the wake
of departing low pressure Sunday morning but again become locally
fresh out of the S Monday through mid-week as another front
approaches from the west. Southerlies continue through the week.
Isolated thunderstorms have been observed along the cold front and
will be possible within the western nearshore waters tonight into
Monday.
Energy associated with the existing NNW swell is small and
concentrated in the shorter periods favoring a slight downward
adjustment to the surf numbers for N facing shores for this
evening. Forerunners associated with a new moderate medium to
long period NW swell have pinged on the NDBC offshore buoys this
afternoon. This energy will build into the nearshore waters
tonight into Sunday. Surf will build rapidly during the morning
peaking near High Surf Advisory thresholds for N and W facing
shores by Sunday afternoon. A combination of moderate NW and N
swells will maintain elevated surf elevated through the first half
of next week.
E shores remain tiny to small given the lack of trade winds but
shorelines exposed to N swells may be slightly elevated through
Wednesday. Surf along S shores will see an increase of short
period wind wave chop mainly over the western islands this weekend
associated with the passing front. A slight lull is expected
Sunday before the next front approaches and increases the wind
waves coming from the south.
&&
.FIRE WEATHER...
Conditions will remain below critical fire weather thresholds
through the forecast period. Winds are expected to remain light
to moderate. Relative humidity will generally remain elevated as
showers periodically move across portions of the state. However,
expect near critical relative humidity to continue along higher
elevations of the Big Island and Maui.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch from midnight HST tonight through late Monday night
for Niihau-Kauai Leeward-Kauai Mountains-Waianae Coast-Oahu
North Shore-Olomana-Central Oahu-Waianae Mountains-Kauai North-
Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-
Koolau Windward-Koolau Leeward.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters.
&&
$$
DISCUSSION...Ahue
AVIATION...Walsh
MARINE...JVC
FIRE WEATHER...Ahue
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
438
FXHW60 PHFO 140115
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
315 PM HST Sat Dec 13 2025
.SYNOPSIS...
An approaching cold front will being enhanced showers and isolated
thunderstorms to the western end of the state through Monday
night. Unsettled wet conditions continue through most of next week
as another front approaches from the northwest, then stalls across
the western half of the state.
&&
.DISCUSSION...
Satellite imagery and the latest surface analysis depicts a cold
front approximately 100 miles northwest of Kauai this afternoon.
Radar imagery shows scattered showers across the leeward Kauai and
Oahu waters moving northeast, but generally remaining offshore.
Southerly winds ahead of the front continue across the state, with
broken to overcast skies over leeward portions of the smaller
islands. The forecast remains on track, and continues to show the
potential for heavy rain and isolated thunderstorms capable of
producing flash flooding across portions of Kauai County and Oahu.
A Flood Watch remains in effect for Niihau, Kauai, and Oahu from
midnight tonight through 6 AM Tuesday morning.
The latest hi-res guidance shows the front reaching Kauai around
midnight tonight, the moving eastward and reaching Oahu around
daybreak on Sunday. The front looks to then briefly stall over
East Oahu Sunday afternoon and evening, before retrograding west
and stalling out in the vicinity of Kauai or Oahu Sunday night
into Monday. There remains good agreement with the evolution of
the upper level support associated with the system as a strong
100+ kt southwesterly jet helps to deepen the front and provide a
narrow corridor of strong uplift. This in turn will result in a
mature jet-front system that will support the development of a
band of heavy rain and isolated thunderstorms. There still remains
some uncertainty where this band of heavy rain will eventually
settle Sunday night into Monday, but the western half of the
state could see anywhere from 1.5 to 3 inches between now and
Monday night, with locally higher amounts possible.
The upper level support is expected to lift north on Tuesday and
bring the surface low with it. The surface front will also lift
and weaken, although lingering moisture will remain in the area
keeping some showers around the area on Tuesday. Another surface
low looks to develop near the dateline on Monday, then move east
through late next week. Guidance continues to show a front
approaching the islands from the northwest mid to late next week,
with the front elongating and stalling over the western half of
the state by late next week. There is still some uncertainty with
how strong this front will be, but expect additional showers and
unsettled weather continue through the rest of the week.
&&
.AVIATION...
Southerly winds have increased this afternoon. Expect elevated
and gusty winds to continue especially across the western half of
the state ahead of a front that is approaching Kauai. This front
will bring low cigs, SHRA and a few tstms. IFR/MVFR conds possible
across the western end, while a few eastern end sites will remain
VFR.
AIRMET Sierra is in effect for mtn obsc for Kauai and Oahu. As
conds deteriorate this may become an IFR AIRMET.
&&
.MARINE...
An approaching front will reach of Kauai late this evening
potentially advancing as far east as Oahu by early Sunday. The
Small Craft Advisory for strong SW winds in advance of the front
has been extended until Monday morning due elevated seas poised to
arrive during Sunday morning. Winds rapidly diminish in the wake
of departing low pressure Sunday morning but again become locally
fresh out of the S Monday through mid-week as another front
approaches from the west. Southerlies continue through the week.
Isolated thunderstorms have been observed along the cold front and
will be possible within the western nearshore waters tonight into
Monday.
Energy associated with the existing NNW swell is small and
concentrated in the shorter periods favoring a slight downward
adjustment to the surf numbers for N facing shores for this
evening. Forerunners associated with a new moderate medium to
long period NW swell have pinged on the NDBC offshore buoys this
afternoon. This energy will build into the nearshore waters
tonight into Sunday. Surf will build rapidly during the morning
peaking near High Surf Advisory thresholds for N and W facing
shores by Sunday afternoon. A combination of moderate NW and N
swells will maintain elevated surf elevated through the first half
of next week.
E shores remain tiny to small given the lack of trade winds but
shorelines exposed to N swells may be slightly elevated through
Wednesday. Surf along S shores will see an increase of short
period wind wave chop mainly over the western islands this weekend
associated with the passing front. A slight lull is expected
Sunday before the next front approaches and increases the wind
waves coming from the south.
&&
.FIRE WEATHER...
Conditions will remain below critical fire weather thresholds
through the forecast period. Winds are expected to remain light
to moderate. Relative humidity will generally remain elevated as
showers periodically move across portions of the state. However,
expect near critical relative humidity to continue along higher
elevations of the Big Island and Maui.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch from midnight HST tonight through late Monday night
for Niihau-Kauai Leeward-Kauai Mountains-Waianae Coast-Oahu
North Shore-Olomana-Central Oahu-Waianae Mountains-Kauai North-
Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-
Koolau Windward-Koolau Leeward.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters.
&&
$$
DISCUSSION...Ahue
AVIATION...Walsh
MARINE...JVC
FIRE WEATHER...Ahue
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office