NWS Bulletins for NPAC - MKWC
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Hawaiian Islands Synoptic Discussion and Guidance
273
FXHW60 PHFO 190120
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
320 PM HST Sat May 18 2024
.SYNOPSIS...
Heavy showers and isolated thunderstorms will remain possible
over Oahu through this evening, while ample moisture over Kauai
County will continue the threat for heavy rain there through
tonight. Expect improving trends from east to west on Sunday. By
Monday all islands will see an improvement in weather conditions
as easterly trade winds return.
&&
.DISCUSSION...
Latest radar and satellite imagery shows heavy showers and
isolated thunderstorms moving over the island of Oahu this
afternoon, with lighter rain observed over Kauai. This moisture is
being drawn northward by a kona low that is located northwest of
the main Hawaiian Islands with a trough located near Kauai.
Additionally, surface convergence from more easterly flow across
the central islands and southerly flow wrapping around the
southern tip of the Big Island has sparked convection within an
unstable environment over the western portion of the state. This
is resulting in the occasional heavy showers and isolated thunder
observed over Oahu today. Some of the hi-res guidance has been
hinting at this possibility over the past day or so as we
transition from the southerly flow back to easterly flow. A Flood
Watch remains in effect for Kauai County through tonight as
pockets of heavy rain will remain possible. Additionally,
convergence upstream of Oahu could continue to produce
occasionally heavy showers moving into Oahu into the evening, but
should trend down during the overnight hours.
High pressure will build in from east to west across the state
Sunday as the kona low shifts north and weakens. Expect more
stabilizing trends with decreasing showers as east to southeast
winds spread across the state on Sunday. By Sunday, the moderate
to heavy rainfall threat will diminish as more stable conditions
fill in across the state.
Easterly trade winds will return across the islands from Monday
onward. Trade wind showers may be somewhat enhanced during the
first half of next week due to lingering moisture and some upper
level instability from a short wave trough. Precipitable water
values will return to normal during the second half of the week,
supporting a more typical trade wind pattern.
&&
.AVIATION...
A trough just west of Kauai will maintain an unstable environment,
especially over the western half of the state. Heavy showers
developed over Oahu earlier today and will continue to impact Oahu
with periods IFR conditions possible in moderate to locally heavy
showers through this evening. Over on Kauai, steady periods of
light to moderate rain is expected to continue through this
evening with a decrease of rain expected late tonight. Periods of
MVFR conditions will be possible with the heavier showers on
Kauai.
A deep upper level trough will continue to produce light to
moderate turbulence across the state from FL280-400 through
Sunday. AIRMET Tango is in effect across the state due to the
upper level turbulence. AIRMET Sierra in effect for mountain
obscurations over most islands except Big Island. Periods of
light to moderate rime icing is expected from Kauai to Oahu in
layer 130-FL220 especially this afternoon through tonight. AIRMET
ZULU is in effect.
&&
.MARINE...
Locally strong E to SE winds will persist through the weekend
before transitioning to easterly early next week. A Small Craft
Advisory remains in effect through Sunday for the windier waters
around Maui County and the Big Island.
Surf along S facing shores will remain elevated through early next
week due to overlapping long-period SSW swells. The first swell
has peaked and the period is gradually shortening. However, ample
energy is still found in the 15-16 second band. In addition, the
second SSW swell will fill in during Sunday, peaking early next
week slightly lower than the present swell. The High Surf Advisory
has been extended through Sunday.
Surf along north facing shores will steadily lower through the
weekend, with a return to a more typical pattern for this time of
year next week.
Surf along east facing shores will remain well below average
through the weekend. An upward trend is possible next week as the
trades return.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for Niihau and Kauai.
High Surf Advisory until 6 PM HST Sunday for south facing shores
of all islands.
Small Craft Advisory until 6 PM HST Sunday for Maui County
Windward Waters-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Kino
MARINE...JVC
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
273
FXHW60 PHFO 190120
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
320 PM HST Sat May 18 2024
.SYNOPSIS...
Heavy showers and isolated thunderstorms will remain possible
over Oahu through this evening, while ample moisture over Kauai
County will continue the threat for heavy rain there through
tonight. Expect improving trends from east to west on Sunday. By
Monday all islands will see an improvement in weather conditions
as easterly trade winds return.
&&
.DISCUSSION...
Latest radar and satellite imagery shows heavy showers and
isolated thunderstorms moving over the island of Oahu this
afternoon, with lighter rain observed over Kauai. This moisture is
being drawn northward by a kona low that is located northwest of
the main Hawaiian Islands with a trough located near Kauai.
Additionally, surface convergence from more easterly flow across
the central islands and southerly flow wrapping around the
southern tip of the Big Island has sparked convection within an
unstable environment over the western portion of the state. This
is resulting in the occasional heavy showers and isolated thunder
observed over Oahu today. Some of the hi-res guidance has been
hinting at this possibility over the past day or so as we
transition from the southerly flow back to easterly flow. A Flood
Watch remains in effect for Kauai County through tonight as
pockets of heavy rain will remain possible. Additionally,
convergence upstream of Oahu could continue to produce
occasionally heavy showers moving into Oahu into the evening, but
should trend down during the overnight hours.
High pressure will build in from east to west across the state
Sunday as the kona low shifts north and weakens. Expect more
stabilizing trends with decreasing showers as east to southeast
winds spread across the state on Sunday. By Sunday, the moderate
to heavy rainfall threat will diminish as more stable conditions
fill in across the state.
Easterly trade winds will return across the islands from Monday
onward. Trade wind showers may be somewhat enhanced during the
first half of next week due to lingering moisture and some upper
level instability from a short wave trough. Precipitable water
values will return to normal during the second half of the week,
supporting a more typical trade wind pattern.
&&
.AVIATION...
A trough just west of Kauai will maintain an unstable environment,
especially over the western half of the state. Heavy showers
developed over Oahu earlier today and will continue to impact Oahu
with periods IFR conditions possible in moderate to locally heavy
showers through this evening. Over on Kauai, steady periods of
light to moderate rain is expected to continue through this
evening with a decrease of rain expected late tonight. Periods of
MVFR conditions will be possible with the heavier showers on
Kauai.
A deep upper level trough will continue to produce light to
moderate turbulence across the state from FL280-400 through
Sunday. AIRMET Tango is in effect across the state due to the
upper level turbulence. AIRMET Sierra in effect for mountain
obscurations over most islands except Big Island. Periods of
light to moderate rime icing is expected from Kauai to Oahu in
layer 130-FL220 especially this afternoon through tonight. AIRMET
ZULU is in effect.
&&
.MARINE...
Locally strong E to SE winds will persist through the weekend
before transitioning to easterly early next week. A Small Craft
Advisory remains in effect through Sunday for the windier waters
around Maui County and the Big Island.
Surf along S facing shores will remain elevated through early next
week due to overlapping long-period SSW swells. The first swell
has peaked and the period is gradually shortening. However, ample
energy is still found in the 15-16 second band. In addition, the
second SSW swell will fill in during Sunday, peaking early next
week slightly lower than the present swell. The High Surf Advisory
has been extended through Sunday.
Surf along north facing shores will steadily lower through the
weekend, with a return to a more typical pattern for this time of
year next week.
Surf along east facing shores will remain well below average
through the weekend. An upward trend is possible next week as the
trades return.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for Niihau and Kauai.
High Surf Advisory until 6 PM HST Sunday for south facing shores
of all islands.
Small Craft Advisory until 6 PM HST Sunday for Maui County
Windward Waters-Alenuihaha Channel-Big Island Windward Waters-
Big Island Leeward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Kino
MARINE...JVC
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office