NWS Bulletins for NPAC - MKWC
Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans:
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
115
FXHW60 PHFO 201300
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
300 AM HST Tue May 20 2025
.SYNOPSIS...
Moderate to locally breezy trades will deliver clouds and showers
to windward and mauka areas through the week, with some decaying
showers reaching leeward areas as well. A few downpours and even a
rumble or two of thunder will be possible Thursday and Friday as a
pair of disturbances aloft move over the island chain. The upper
level disturbance will gradually weaken over the weekend into
early next week, and precipitable waters values will similarly
slowly decrease. This should bring a steady decrease in shower
coverage and intensity with progressively nicer weather as we head
through the Memorial Day weekend.
&&
.DISCUSSION...
Currently at the surface, a 1030 mb high is centered around 1750
miles northeast of Honolulu, while a trough of low pressure is
located around 1500 miles west of Kauai. The resulting gradient
is driving moderate trade winds across the island chain early
this morning. Infrared satellite imagery shows mostly cloudy
conditions over windward and mauka areas, with partly cloudy
skies in most leeward locales. Radar imagery shows scattered to
numerous showers moving into windward slopes and coasts, with a
considerable amount of leeward push across Kauai and Oahu, and
lesser leeward spread over Maui County and the Big Island. Main
short term focus revolves around rain chances and thunder
potential.
High pressure will persist to the northeast and north of the
islands throughout the forecast period. This will maintain
moderate to locally breezy trade winds, with only minor
fluctuations in strength from day to day. A wetter than normal
trade wind pattern will persist through the remainder of the work
week, as a pair of disturbances aloft keep inversion heights
elevated and conditions somewhat unstable. In fact, with H7-H5
lapse rates increasing to 6.5 - 7.0 C/km and surfaced based CAPE
values climbing to around 1000-1500 J/KG, some locally heavy
downpours and even a few rumbles of thunder will be possible
across portions of the state late Wednesday night through Friday
evening. The upper level disturbance will gradually weaken over
the weekend into early next week, and precipitable waters values
will similarly slowly decrease. This should bring a steady
decrease in shower coverage and intensity with progressively nicer
weather as we head through the Memorial Day weekend.
&&
.AVIATION...
Moderate to locally breezy trade winds will persist during the
next 24 hours, strongest and most gusty from mid morning through
late afternoon. Low clouds and showers will favor windward and
mauka areas, particularly overnight and during the morning hours,
with showers reaching leeward communities rather regularly.
AIRMET Sierra is now in effect for mountain obscuration across
windward sections of Kauai, Oahu, Molokai, Maui and the Big
Island. Conditions should improve in most areas by late this
morning.
&&
.MARINE...
Surface high pressure building in far north of the islands will
help maintain moderate to locally strong trades through a
majority of this week. A Small Craft Advisory (SCA) has been
issued for the typically windy waters around the Big Island and
Maui through Wednesday morning, but will likely need to be
extended through at least Friday. The high is forecast to retreat
westward during the weekend, favoring a slight decrease in winds.
Surf along south facing shores will remain just below seasonal
average through Thursday. A small, long period, south southwest
swell will enter the waters by late Thursday and bring near normal
surf along south facing shores though early this weekend. Surf
will then decline Sunday and remain small into early next week.
East shore surf will remain near seasonal average during the next
couple of days. A gradual decline in east shore surf is expected
during the weekend and early next week. Tiny surf will prevail
along north facing shores this week.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel.
&&
$$
DISCUSSION...Jelsema
AVIATION...Jelsema
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
115
FXHW60 PHFO 201300
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
300 AM HST Tue May 20 2025
.SYNOPSIS...
Moderate to locally breezy trades will deliver clouds and showers
to windward and mauka areas through the week, with some decaying
showers reaching leeward areas as well. A few downpours and even a
rumble or two of thunder will be possible Thursday and Friday as a
pair of disturbances aloft move over the island chain. The upper
level disturbance will gradually weaken over the weekend into
early next week, and precipitable waters values will similarly
slowly decrease. This should bring a steady decrease in shower
coverage and intensity with progressively nicer weather as we head
through the Memorial Day weekend.
&&
.DISCUSSION...
Currently at the surface, a 1030 mb high is centered around 1750
miles northeast of Honolulu, while a trough of low pressure is
located around 1500 miles west of Kauai. The resulting gradient
is driving moderate trade winds across the island chain early
this morning. Infrared satellite imagery shows mostly cloudy
conditions over windward and mauka areas, with partly cloudy
skies in most leeward locales. Radar imagery shows scattered to
numerous showers moving into windward slopes and coasts, with a
considerable amount of leeward push across Kauai and Oahu, and
lesser leeward spread over Maui County and the Big Island. Main
short term focus revolves around rain chances and thunder
potential.
High pressure will persist to the northeast and north of the
islands throughout the forecast period. This will maintain
moderate to locally breezy trade winds, with only minor
fluctuations in strength from day to day. A wetter than normal
trade wind pattern will persist through the remainder of the work
week, as a pair of disturbances aloft keep inversion heights
elevated and conditions somewhat unstable. In fact, with H7-H5
lapse rates increasing to 6.5 - 7.0 C/km and surfaced based CAPE
values climbing to around 1000-1500 J/KG, some locally heavy
downpours and even a few rumbles of thunder will be possible
across portions of the state late Wednesday night through Friday
evening. The upper level disturbance will gradually weaken over
the weekend into early next week, and precipitable waters values
will similarly slowly decrease. This should bring a steady
decrease in shower coverage and intensity with progressively nicer
weather as we head through the Memorial Day weekend.
&&
.AVIATION...
Moderate to locally breezy trade winds will persist during the
next 24 hours, strongest and most gusty from mid morning through
late afternoon. Low clouds and showers will favor windward and
mauka areas, particularly overnight and during the morning hours,
with showers reaching leeward communities rather regularly.
AIRMET Sierra is now in effect for mountain obscuration across
windward sections of Kauai, Oahu, Molokai, Maui and the Big
Island. Conditions should improve in most areas by late this
morning.
&&
.MARINE...
Surface high pressure building in far north of the islands will
help maintain moderate to locally strong trades through a
majority of this week. A Small Craft Advisory (SCA) has been
issued for the typically windy waters around the Big Island and
Maui through Wednesday morning, but will likely need to be
extended through at least Friday. The high is forecast to retreat
westward during the weekend, favoring a slight decrease in winds.
Surf along south facing shores will remain just below seasonal
average through Thursday. A small, long period, south southwest
swell will enter the waters by late Thursday and bring near normal
surf along south facing shores though early this weekend. Surf
will then decline Sunday and remain small into early next week.
East shore surf will remain near seasonal average during the next
couple of days. A gradual decline in east shore surf is expected
during the weekend and early next week. Tiny surf will prevail
along north facing shores this week.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel.
&&
$$
DISCUSSION...Jelsema
AVIATION...Jelsema
MARINE...Thomas
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office