NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
632
FXHW60 PHFO 191915
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
915 AM HST Sun Apr 19 2026
.SYNOPSIS...
An upper-level trough will bring increased high clouds and renewed
chances for isolated heavy showers and thunderstorms this afternoon
and Monday. Light winds favor chances for mainly afternoon showers
Tuesday and Wednesday, followed by rebuilding trade winds Thursday
and Friday.
&&
.SHORT TERM UPDATE...
In general the forecast is on track, so not anticipating any
updates this morning. An upper level trough to the west continues
to spread high clouds over the state. Thunderstorms are found
close to the upper level trough. We continue to monitor for any
thunderstorms that could develop closer to the islands this
afternoon through tomorrow.
&&
.PREV DISCUSSION...
Issued at 310 AM HST Sun Apr 19 2026
Today and tomorrow, trades will weaken further and will shift out
of the east-southeast across the western half of the island
chain, while another upper-level trough brings instability, mainly
tonight into Monday morning. For now, it appears that the deepest
moisture and highest chances for widespread rainfall will remain
along the surface trough northwest of Kauai, but isolated heavy
showers or a thunderstorm remain possible around Kauai. Elsewhere,
expect afternoon interior showers and possibly a thunderstorm on
Big Island, and another item to monitor will be a chance for
localized anchored heavy showers along the Koolau Mountains of
Oahu tonight. Even though moisture does not appear to be
significant on Oahu, the expected veering flow with height has a
tendency to produce heavy rain events on the Koolau.
Chances for heavy rainfall look to diminish Tuesday and Wednesday.
The upper level trough should move off to the east late Monday,
allowing a weak ridge aloft to settle over the state. The GFS and
ECMWF are hinting that the surface trough that had been lingering
northwest of Kauai will be pushed over the western end of the
island chain. This would favor light and variable winds over most
areas with higher rainfall chances over island interiors during
the late morning and afternoon hours. Trade winds are expected to
rebuild Thursday and Friday.
&&
.AVIATION...
Issued at 310 AM HST Sun Apr 19 2026
Predominately light northeasterly winds among some land-sea
breezes will remain in place through the next several days under
high pressure well northeast of the Hawaiian Islands and a surface
trough lingering to the west. Some terminals may experience some
mid- to high-clouds and embedded light showers, resulting in
brief periods of MVFR conditions. Otherwise, expect VFR conditions
to prevail across most terminals through the period.
No AIRMETs in effect.
&&
.MARINE...
A trough approaching slowly from the west will allow winds to
veer east southeasterly and weaken later today through early next
week across the local waters. This feature will also bring a
slight chance of thunderstorms to the waters surrounding Kauai
this afternoon through mid day Monday. By Thursday, high pressure
ridging builds back in north of the state with fresh easterly
trade winds returning to the region lasting through next weekend.
Swell, from every direction, and surf will remain very small
through late Monday. A small, medium period, northwest swell will
move into the region by Monday night and continue through
Wednesday. A moderate, medium period northeast swell arrives
Tuesday and peaks on Wednesday, bringing moderate surf to north-
facing shores, before slowly declining through the end of the
week.
A series of overlapping small south swells will move into the
region this week keeping surf heights on the small side. Surf
heights along east facing shores also remain small due to weaker
trade winds until the arrival of the small medium period northeast
swell building into the Hawaii region from Tuesday through
Thursday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM UPDATE...M Ballard
DISCUSSION...Walsh
AVIATION...Pierce
MARINE...Thomas
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
632
FXHW60 PHFO 191915
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
915 AM HST Sun Apr 19 2026
.SYNOPSIS...
An upper-level trough will bring increased high clouds and renewed
chances for isolated heavy showers and thunderstorms this afternoon
and Monday. Light winds favor chances for mainly afternoon showers
Tuesday and Wednesday, followed by rebuilding trade winds Thursday
and Friday.
&&
.SHORT TERM UPDATE...
In general the forecast is on track, so not anticipating any
updates this morning. An upper level trough to the west continues
to spread high clouds over the state. Thunderstorms are found
close to the upper level trough. We continue to monitor for any
thunderstorms that could develop closer to the islands this
afternoon through tomorrow.
&&
.PREV DISCUSSION...
Issued at 310 AM HST Sun Apr 19 2026
Today and tomorrow, trades will weaken further and will shift out
of the east-southeast across the western half of the island
chain, while another upper-level trough brings instability, mainly
tonight into Monday morning. For now, it appears that the deepest
moisture and highest chances for widespread rainfall will remain
along the surface trough northwest of Kauai, but isolated heavy
showers or a thunderstorm remain possible around Kauai. Elsewhere,
expect afternoon interior showers and possibly a thunderstorm on
Big Island, and another item to monitor will be a chance for
localized anchored heavy showers along the Koolau Mountains of
Oahu tonight. Even though moisture does not appear to be
significant on Oahu, the expected veering flow with height has a
tendency to produce heavy rain events on the Koolau.
Chances for heavy rainfall look to diminish Tuesday and Wednesday.
The upper level trough should move off to the east late Monday,
allowing a weak ridge aloft to settle over the state. The GFS and
ECMWF are hinting that the surface trough that had been lingering
northwest of Kauai will be pushed over the western end of the
island chain. This would favor light and variable winds over most
areas with higher rainfall chances over island interiors during
the late morning and afternoon hours. Trade winds are expected to
rebuild Thursday and Friday.
&&
.AVIATION...
Issued at 310 AM HST Sun Apr 19 2026
Predominately light northeasterly winds among some land-sea
breezes will remain in place through the next several days under
high pressure well northeast of the Hawaiian Islands and a surface
trough lingering to the west. Some terminals may experience some
mid- to high-clouds and embedded light showers, resulting in
brief periods of MVFR conditions. Otherwise, expect VFR conditions
to prevail across most terminals through the period.
No AIRMETs in effect.
&&
.MARINE...
A trough approaching slowly from the west will allow winds to
veer east southeasterly and weaken later today through early next
week across the local waters. This feature will also bring a
slight chance of thunderstorms to the waters surrounding Kauai
this afternoon through mid day Monday. By Thursday, high pressure
ridging builds back in north of the state with fresh easterly
trade winds returning to the region lasting through next weekend.
Swell, from every direction, and surf will remain very small
through late Monday. A small, medium period, northwest swell will
move into the region by Monday night and continue through
Wednesday. A moderate, medium period northeast swell arrives
Tuesday and peaks on Wednesday, bringing moderate surf to north-
facing shores, before slowly declining through the end of the
week.
A series of overlapping small south swells will move into the
region this week keeping surf heights on the small side. Surf
heights along east facing shores also remain small due to weaker
trade winds until the arrival of the small medium period northeast
swell building into the Hawaii region from Tuesday through
Thursday.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM UPDATE...M Ballard
DISCUSSION...Walsh
AVIATION...Pierce
MARINE...Thomas
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office