NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
818
FXHW60 PHFO 020617
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
817 PM HST Sat Jun 1 2024
.SYNOPSIS...
Breezy trades continue through mid-week before weakening and
potentially giving way to a land and sea breeze pattern. A passing
upper trough may allow some showers to be locally heavy Sunday
through Tuesday, especially over interior Big Island where there
will be also be a chance for afternoon thunderstorms.
&&
.DISCUSSION...
Some changes to the forecast were made this evening to ensure more
consistent sky and qpf parameters given the current PoP forecast
throughout the forecast period. Not anticipating any significant
updates with the morning package.
High pressure remains far to the northeast of the islands, with a
ridge north of 30N. The resultant pressure gradient over the
islands is maintaining a breezy trade wind pattern. Satellite
derived precipitable water shows a drier airmass has moved over
the islands, even since the afternoon soundings. The most moisture
remains near the Big Island, and to a lesser extent Maui. That
is reflected in rainfall amounts over the last several hours with
some windward locations having received over .5 inches in the
last 6 hours. Anticipate showers to continue overnight, mainly
over the windward slopes, of the Big Island and Maui. The
remaining islands will have some clouds overhead, but the chance
for showers will be significantly lower.
A mid to upper level trough moving over the islands from the east
overnight will lead to an increasing unstable airmass over the
islands Sunday through Tuesday. The trough is expected to sharpen
and pivot over the islands during this time, before lifting north
and then east away from the region. The global models are in good
agreement that this trough will bring colder temperatures to 500
mb. The ECMWF keeps temperatures around -10/-11C, while the GFS
brings in even colder temperatures of -12/-13C. These
temperatures are significantly colder than normal for June. At
700 mb there isn't much different in the temperatures between
these models with temperature getting to around 4/6C which is
colder than normal but not as climatologically colder. Additional
the coldest temperatures at 700 mb look to be focused near Kauai,
while the colder 500 mb temperatures reach most of the islands.
Thunderstorms were added with the afternoon package to the Big
Island forecast for Monday and Tuesday afternoon, with the best
chance being Tuesday afternoon. Leeward island plumes over the
nearshore waters will also be candidates for nocturnal
thunderstorm activity during this time, however confidence is
lower so that is not currently reflected in the forecast.
The second half of the week will see the a new mid-level ridge
setting up far northwest of the islands, as a front north of the
islands weakens to a trough. This will cause our winds to weaken
and turn to the southeast. This could lead to some land and sea
breezes over the islands. With a decrease in precipitable water
and a more stable airmass overhead, expect a decrease in shower
activity, with clouds and showers more likely during the afternoon
and evening hours over interior and southeast facing portions of
the islands.
Today marks the start of hurricane season in the central North
Pacific basin. It was 67 years ago today, in 1957, when the
Weather Bureau Airport Station (which later became the National
Weather Service Forecast Office) began Central Pacific Hurricane
Center operations. Visit hurricanes.gov throughout the season,
which continues through November 30, to stay informed.
&&
.AVIATION...
Breezy to strong trades will continue, as a surface high moves
closer to the state from the northeast. Low cigs and SHRA will
favor windward and mauka areas with periods of MVFR conds possible
in any SHRA. VFR conds should prevail elsewhere.
AIRMET Sierra is in effect for mtn obsc for windward Big Island
and N thru SE sections of the smaller islands.
AIRMET Tango remains in effect for moderate low- level turb S thru
W of terrain, as well as for moderate turb between FL300-FL400.
AMD NOT SKED for PMDY as equipment remains unavailable with no
time table for return to service.
&&
.MARINE...
A 1029 mb surface high centered about 900 nm NE of the islands
will stagnate through the remainder of this weekend. The high is
expected to weaken slightly on Monday, but will still help to
support fresh to locally strong ENE trade winds through the day
Tuesday. A Small Craft Advisory (SCA) remains in effect for most
zones through early Sunday and will likely need to be extended for
the typically windier zones around Maui and the Big Island into
early next week. On Wednesday, a frontal system approaching from
the northwest will allow the high to weaken significantly, and
lead to light and variable winds through the end of the week.
An extended period of elevated surf along S facing shores is now
underway, with numerous swell pulses expected, mainly from the
SSW. A High Surf Advisory (HSA) is likely to be needed for the
largest of the swells, which may not arrive until next weekend.
However, there is potential for HSA-level surf before then as the
storm track near New Zealand has been conducive for S swell
production for Hawaii for the last week or so. Nearshore buoys S
of the islands continue to indicate increased energy in the
longer 15-17 second period bands this evening, equating to
elevated surf that is below HSA levels. While the larger sets of
waves remain inconsistent due to the long period, wave heights are
definitely on the increase from yesterday. This swell likely peak
early Sunday into Monday, then gradually ease Tuesday before
additional long-period swells arrive.
A strong, slow-moving low in the distant NW Pacific generated what
will be a small NW swell when it arrives in the islands Monday
and Tuesday (3 to 4 foot medium period swell from 320 direction),
with the potential for a small follow- up NW swell later in the
week. Trade winds will continue to generate short- period wind
waves that will support choppy surf along exposed E facing shores
the next couple of days.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward
Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-
Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward
Waters-Big Island Southeast Waters.
&&
$$
DISCUSSION...M Ballard
AVIATION...Walsh
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
818
FXHW60 PHFO 020617
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
817 PM HST Sat Jun 1 2024
.SYNOPSIS...
Breezy trades continue through mid-week before weakening and
potentially giving way to a land and sea breeze pattern. A passing
upper trough may allow some showers to be locally heavy Sunday
through Tuesday, especially over interior Big Island where there
will be also be a chance for afternoon thunderstorms.
&&
.DISCUSSION...
Some changes to the forecast were made this evening to ensure more
consistent sky and qpf parameters given the current PoP forecast
throughout the forecast period. Not anticipating any significant
updates with the morning package.
High pressure remains far to the northeast of the islands, with a
ridge north of 30N. The resultant pressure gradient over the
islands is maintaining a breezy trade wind pattern. Satellite
derived precipitable water shows a drier airmass has moved over
the islands, even since the afternoon soundings. The most moisture
remains near the Big Island, and to a lesser extent Maui. That
is reflected in rainfall amounts over the last several hours with
some windward locations having received over .5 inches in the
last 6 hours. Anticipate showers to continue overnight, mainly
over the windward slopes, of the Big Island and Maui. The
remaining islands will have some clouds overhead, but the chance
for showers will be significantly lower.
A mid to upper level trough moving over the islands from the east
overnight will lead to an increasing unstable airmass over the
islands Sunday through Tuesday. The trough is expected to sharpen
and pivot over the islands during this time, before lifting north
and then east away from the region. The global models are in good
agreement that this trough will bring colder temperatures to 500
mb. The ECMWF keeps temperatures around -10/-11C, while the GFS
brings in even colder temperatures of -12/-13C. These
temperatures are significantly colder than normal for June. At
700 mb there isn't much different in the temperatures between
these models with temperature getting to around 4/6C which is
colder than normal but not as climatologically colder. Additional
the coldest temperatures at 700 mb look to be focused near Kauai,
while the colder 500 mb temperatures reach most of the islands.
Thunderstorms were added with the afternoon package to the Big
Island forecast for Monday and Tuesday afternoon, with the best
chance being Tuesday afternoon. Leeward island plumes over the
nearshore waters will also be candidates for nocturnal
thunderstorm activity during this time, however confidence is
lower so that is not currently reflected in the forecast.
The second half of the week will see the a new mid-level ridge
setting up far northwest of the islands, as a front north of the
islands weakens to a trough. This will cause our winds to weaken
and turn to the southeast. This could lead to some land and sea
breezes over the islands. With a decrease in precipitable water
and a more stable airmass overhead, expect a decrease in shower
activity, with clouds and showers more likely during the afternoon
and evening hours over interior and southeast facing portions of
the islands.
Today marks the start of hurricane season in the central North
Pacific basin. It was 67 years ago today, in 1957, when the
Weather Bureau Airport Station (which later became the National
Weather Service Forecast Office) began Central Pacific Hurricane
Center operations. Visit hurricanes.gov throughout the season,
which continues through November 30, to stay informed.
&&
.AVIATION...
Breezy to strong trades will continue, as a surface high moves
closer to the state from the northeast. Low cigs and SHRA will
favor windward and mauka areas with periods of MVFR conds possible
in any SHRA. VFR conds should prevail elsewhere.
AIRMET Sierra is in effect for mtn obsc for windward Big Island
and N thru SE sections of the smaller islands.
AIRMET Tango remains in effect for moderate low- level turb S thru
W of terrain, as well as for moderate turb between FL300-FL400.
AMD NOT SKED for PMDY as equipment remains unavailable with no
time table for return to service.
&&
.MARINE...
A 1029 mb surface high centered about 900 nm NE of the islands
will stagnate through the remainder of this weekend. The high is
expected to weaken slightly on Monday, but will still help to
support fresh to locally strong ENE trade winds through the day
Tuesday. A Small Craft Advisory (SCA) remains in effect for most
zones through early Sunday and will likely need to be extended for
the typically windier zones around Maui and the Big Island into
early next week. On Wednesday, a frontal system approaching from
the northwest will allow the high to weaken significantly, and
lead to light and variable winds through the end of the week.
An extended period of elevated surf along S facing shores is now
underway, with numerous swell pulses expected, mainly from the
SSW. A High Surf Advisory (HSA) is likely to be needed for the
largest of the swells, which may not arrive until next weekend.
However, there is potential for HSA-level surf before then as the
storm track near New Zealand has been conducive for S swell
production for Hawaii for the last week or so. Nearshore buoys S
of the islands continue to indicate increased energy in the
longer 15-17 second period bands this evening, equating to
elevated surf that is below HSA levels. While the larger sets of
waves remain inconsistent due to the long period, wave heights are
definitely on the increase from yesterday. This swell likely peak
early Sunday into Monday, then gradually ease Tuesday before
additional long-period swells arrive.
A strong, slow-moving low in the distant NW Pacific generated what
will be a small NW swell when it arrives in the islands Monday
and Tuesday (3 to 4 foot medium period swell from 320 direction),
with the potential for a small follow- up NW swell later in the
week. Trade winds will continue to generate short- period wind
waves that will support choppy surf along exposed E facing shores
the next couple of days.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward
Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-
Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward
Waters-Big Island Southeast Waters.
&&
$$
DISCUSSION...M Ballard
AVIATION...Walsh
MARINE...Thomas
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office