NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
912
FXHW60 PHFO 260629
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
829 PM HST Sat May 25 2024
.SYNOPSIS...
Broad high pressure north and northeast of the state will maintain
moderate to locally breezy easterly trade winds through the week.
Showers will mainly favor windward slopes, with areas of high
clouds passing overhead at times.
&&
.DISCUSSION...
Moderate to locally breezy easterly trade winds remain in place,
with little change expected through the holiday weekend. The trades
are being driven by broad surface high pressure sitting nearly
1600 miles north of the state. A surface trough parked about 600
miles west of Kauai is causing the winds to be more easterly than
usual, especially over the western end of the island chain. Mid-
level ridging over the islands is maintaining somewhat stable
conditions with shallow moisture moving along the trade wind flow.
This will continue to focus modest rainfall of around a quarter
of an inch or less per day across most windward slopes.
An upper-level trough generally collocated with the surface trough
continues to produce heavy showers and thunderstorms about 200
miles west of Kauai. Westerly winds aloft are sending high clouds
from this area over Kauai and Oahu, while a separate shield of
thin high clouds is streaming over the Big Island. Thunderstorm
activity will remain west of the state through the holiday weekend,
but the inversion could be weakened at times near Kauai, where
brief periods of enhanced showers will be possible. In addition,
expect spotty afternoon and evening showers, some briefly heavy,
across leeward Big Island.
Little change is expected from Tuesday onward. The surface high
will settle far northeast of the state and hold into Friday, while
the surface trough lingers west of the islands, resulting in breezy
easterly trade winds. The nearby upper-level trough will weaken
around mid-week, leading to greater stability and supporting a
more typical trade shower pattern favoring windward slopes.
&&
.AVIATION...
A fairly stable pattern will remain over the state into next week
with some passing high clouds overhead. Shallow moisture embedded
within the trade wind flow will allow for SHRA over windward and
mauka areas. VFR conds should prevail over most locations, with
MVFR conds possible in any SHRA.
AIRMET Sierra is in effect for mtn obsc for, windward Big Island
and NE through SE of Kauai and Oahu.
AIRMET Tango remains in effect for mod low-level turb downwind of
island terrain. This AIRMET will likely remain in effect though
much of next week.
&&
.MARINE...
Moderate to strong easterly trades will continue through the
upcoming week as the surface ridge remains positioned north of the
state. The strongest winds are expected over the windier waters
around Maui County and the Big Island, supporting the Small Craft
Advisory. The lightest winds are anticipated over the Kauai waters,
fluctuating between east and east-southeast over the next few
days due to a persistent surface trough to the west.
Surf along exposed south-facing shores will remain small throughout
much of the week, mainly due to a combination of background south-
southwest and southeast swell energy. An upward trend is expected
from Friday through the first week of June due to an active pattern
unfolding within our swell window near New Zealand.
Altimeter and ASCAT passes over the past 24 hours reflected the
potential for next weekend, showing a broad swath of gales with
seas up to 30 feet focused on the state within the 190-200 degree
directional bands. This will mark the beginning of a long-lived
event with additional reinforcements expected within the same area
over the next several days.
Surf along exposed east-facing shores will remain small and choppy
throughout the week as the trades persist.
Surf along exposed north-facing shores may increase slightly from
late Sunday through Monday due to a small, medium-period northwest
swell expected. Otherwise, summertime conditions are anticipated
with minimal surf expected.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Monday for Pailolo Channel-
Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast
Waters.
&&
$$
DISCUSSION...TS
AVIATION...SMW
MARINE...Gibbs
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
912
FXHW60 PHFO 260629
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
829 PM HST Sat May 25 2024
.SYNOPSIS...
Broad high pressure north and northeast of the state will maintain
moderate to locally breezy easterly trade winds through the week.
Showers will mainly favor windward slopes, with areas of high
clouds passing overhead at times.
&&
.DISCUSSION...
Moderate to locally breezy easterly trade winds remain in place,
with little change expected through the holiday weekend. The trades
are being driven by broad surface high pressure sitting nearly
1600 miles north of the state. A surface trough parked about 600
miles west of Kauai is causing the winds to be more easterly than
usual, especially over the western end of the island chain. Mid-
level ridging over the islands is maintaining somewhat stable
conditions with shallow moisture moving along the trade wind flow.
This will continue to focus modest rainfall of around a quarter
of an inch or less per day across most windward slopes.
An upper-level trough generally collocated with the surface trough
continues to produce heavy showers and thunderstorms about 200
miles west of Kauai. Westerly winds aloft are sending high clouds
from this area over Kauai and Oahu, while a separate shield of
thin high clouds is streaming over the Big Island. Thunderstorm
activity will remain west of the state through the holiday weekend,
but the inversion could be weakened at times near Kauai, where
brief periods of enhanced showers will be possible. In addition,
expect spotty afternoon and evening showers, some briefly heavy,
across leeward Big Island.
Little change is expected from Tuesday onward. The surface high
will settle far northeast of the state and hold into Friday, while
the surface trough lingers west of the islands, resulting in breezy
easterly trade winds. The nearby upper-level trough will weaken
around mid-week, leading to greater stability and supporting a
more typical trade shower pattern favoring windward slopes.
&&
.AVIATION...
A fairly stable pattern will remain over the state into next week
with some passing high clouds overhead. Shallow moisture embedded
within the trade wind flow will allow for SHRA over windward and
mauka areas. VFR conds should prevail over most locations, with
MVFR conds possible in any SHRA.
AIRMET Sierra is in effect for mtn obsc for, windward Big Island
and NE through SE of Kauai and Oahu.
AIRMET Tango remains in effect for mod low-level turb downwind of
island terrain. This AIRMET will likely remain in effect though
much of next week.
&&
.MARINE...
Moderate to strong easterly trades will continue through the
upcoming week as the surface ridge remains positioned north of the
state. The strongest winds are expected over the windier waters
around Maui County and the Big Island, supporting the Small Craft
Advisory. The lightest winds are anticipated over the Kauai waters,
fluctuating between east and east-southeast over the next few
days due to a persistent surface trough to the west.
Surf along exposed south-facing shores will remain small throughout
much of the week, mainly due to a combination of background south-
southwest and southeast swell energy. An upward trend is expected
from Friday through the first week of June due to an active pattern
unfolding within our swell window near New Zealand.
Altimeter and ASCAT passes over the past 24 hours reflected the
potential for next weekend, showing a broad swath of gales with
seas up to 30 feet focused on the state within the 190-200 degree
directional bands. This will mark the beginning of a long-lived
event with additional reinforcements expected within the same area
over the next several days.
Surf along exposed east-facing shores will remain small and choppy
throughout the week as the trades persist.
Surf along exposed north-facing shores may increase slightly from
late Sunday through Monday due to a small, medium-period northwest
swell expected. Otherwise, summertime conditions are anticipated
with minimal surf expected.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Monday for Pailolo Channel-
Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast
Waters.
&&
$$
DISCUSSION...TS
AVIATION...SMW
MARINE...Gibbs
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office