Severe Thunderstorm Warning 4, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
1001 AM HST Mon Dec 19 2022

.SYNOPSIS...
Numerous showers, heavy at times, and thunderstorms will continue
today as a kona storm moves through the region. Bands of strong
thunderstorms are moving through islands along and just ahead of
the vigorous cold front which is now approaching Oahu and will
sweep through the rest of the state from northwest to southeast
today. Isolated severe thunderstorms are expected with the main
threats being damaging winds and small hail. Strong southwest to
west winds will continue through this afternoon and possibly
tonight wind wind gusts of 60 mph possible down wind of any
terrain. Weather conditions will improve over the western islands
later this afternoon and evening and improve across the rest of
the state by Tuesday morning. Fair weather and light winds
expected from Wednesday through the weekend.

&&

.DISCUSSION...
We have updated the forecast to expand and extend our Severe
Thunderstorm Watch through 2PM this afternoon which includes
Kauai, Oahu and Maui counties and the adjacent waters. This
mornings radar and satellite imagery shows scattered thunderstorms
all across the state with the main impacts being damaging winds
in excess of 60 mph. A few isolated storms are also showing hail
signatures with hail sizes of up to 1 inch possible. Latest 18Z
sounding from Lihue shows a decreasing threat for severe
thunderstorms due to a decrease of mixed layer CAPE. The severe
threat should decrease over Kauai soon and likely decrease over
Oahu by early afternoon. The threat for severe will continue over
Maui county through this afternoon and possible expand towards the
Big Island later today.

Latest satellite imagery shows the center of the mid-latitude
cyclone very well and the low remains centered near 32N162W and
will be moving eastward slowly. Besides the severe thunderstorm
threat, the main threat that has been impacting many people across
the state is the wind threat. We have seen numerous power outages
since last night mainly over areas downwind of terrain and the
threat for damaging winds will likely continue for these areas
through this afternoon and possibly tonight. The current High
Wind Warning for the state of Hawaii is in effect through 6 PM
today and we may need to extend the warning. Southwest winds of 25
to 40 mph with gusts up to 60 mph is expected along many of our
typical Windward areas and the wind direction will be shifting
toward the west-northwest today as the front makes it way through
the state. Latest observations show the front has made its way
through Kauai and is now approaching Oahu. The front should make
its way through Maui counties early this afternoon and the Big
Island late this afternoon or evening. Some of our strongest wind
gusts will be possible as the front pushes through the area.

Last but not least, the potential for flash flooding will continue
to exists but with storms moving at speeds over 40 to 50 mph, the
heavy rain is not lasting very long. Pockets of intense rainfall
is occurring with these showers and thunderstorms and if a
cluster of storms hold over any given area, it will not take long
to produce flash flooding over the already saturated soils. The
potential threat for flash flooding will begin to shift toward the
eastern half of the state during the afternoon.

On Tuesday, the mid-latitude cyclone into midweek. Well-mixed,
gusty westerlies build in behind the cold front and focus showers
over leeward slopes through Tuesday. Fair weather with much
lighter winds are expected by Wednesday. Beyond Wednesday, we are
looking at a progressive pattern to continue in the North Pacific,
which will keep trade winds out of the forecast through rest of
the week. Another front could approach the state towards the end
of the week, through most of the moisture and instability looks to
stay well north of the state.

&&

.AVIATION...
A strong cold front and an upper-level trough associated with a
deep low pressure system continues to move rapidly toward the
east-southeast over the smaller islands. Unstable atmospheric
conditions and enhanced moisture are producing widespread cloud
cover and rainfall along with thunderstorms ahead of the front.
This is a high impact weather event, which has been producing
scattered thunderstorms across the island chain. Some storms have
been severe with the potential to produce damaging winds and
large hail. All aviation interests are urged to monitor the latest
forecasts, and use extra caution during the next 24 hours. SIGMET
X-Ray has been issued across all of the main Hawaiian Islands and
areas to the east due to thunderstorm activity this morning, and
this SIGMET is likely to remain in effect into the afternoon.
Remember that any SIGMET issued for thunderstorms also implies
that there is potential for severe turbulence, icing, and wind
shear.

Widespread MVFR conditions, and localized IFR conditions, due to
low ceilings and reduced visibilities are occurring across large
portions of the state with intermittent breaks in between lines of
storms. Regardless, AIRMET Sierra remains in effect for mountain
obscuration above 2,000 feet for most islands. This AIRMET is
likely to remain in effect for most of the state into this
afternoon. We have also included the mention of light icing
occurring in clouds across most of the state in the layer from
12,000 to 22,000 feet in AIRMET Zulu.

As the front continues to move down the island chain, expect
significant strengthening of the low-level southwest to west
winds. AIRMET Tango is currently in effect for Tempo moderate
mechanical low-level turbulence below 9,000 feet northwest
through southeast of the higher terrain on all islands. AIRMET
Tango is also in effect for sustained wind speeds of 30kt or
greater. Finally, AIRMET Tango is also included for tempo
moderate upper-level turbulence in the layer from 18,000 to 30,000
feet even for areas outside of thunderstorms.

&&

.MARINE...
A cold front across the western islands will continue to move
southeast across the rest of the main island chain today,
producing a wide array of marine hazards. These include the
potential for gusty winds, hail and waterspouts in and around
strong to severe thunderstorms, sustained near-gale to gale-force
southwest to west winds, as well as rapidly increasing seas and
surf. A Gale warning continues for all Hawaiian waters through
this afternoon. Additionally, a High Surf Warning (HSW) for
exposed north and west facing shores is in effect for a long lived
northwest swell through Tuesday afternoon. Less exposed
shorelines may need a High Surf Advisory (HSA), to be issued
later, as the swell builds down the island chain.

Even after the front moves east of the islands, west winds are
expected to remain strong to near-gale on Tuesday as low pressure
passes eastward a couple hundred miles north of the islands. Winds
will decline Tuesday night into Wednesday as the low departs to
the northeast and a ridge builds over the area.

The strong low pushing the cold front over the islands will
produce a long-lived and extra-large northwest swell that will
rapidly build into the islands and bring surf heights above High
Surf Warning (HSW) levels. There is high potential for wave run-
up onto vulnerable roadways and coastal areas in the HSW areas,
with the most likely time for these impacts being tonight into
Tuesday morning during high tide. This swell is expected to drop
below warning thresholds Tuesday night into Wednesday. Expect
another large northwest swell towards the end of the week near
High Surf Advisory (HSA) levels. Surf along south and west facing
shores will also see an increase in short-period wind waves
tonight into Tuesday due to the strong onshore winds.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SEVERE THUNDERSTORM WATCH 2 IN EFFECT UNTIL 2 PM HST THIS
AFTERNOON FOR KAUAI OAHU AND MAUI COUNTIES AND ADJACENT WATERS.

Flood Watch through late tonight for all Hawaiian Islands.

High Wind Warning until 6 PM HST this evening for all Hawaiian
Islands.

High Surf Warning until 6 PM HST Tuesday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Olomana-Maui Windward West-
Kauai North-Molokai Windward-Molokai North-Molokai West- Windward
Haleakala.

High Wind Warning until 6 AM HST Tuesday for Haleakala Summit.

High Wind Warning until 6 AM HST Wednesday for Big Island
Summits.

Winter Storm Warning until 6 AM HST Tuesday for Big Island
Summits.

Gale Warning until 6 PM HST this evening for all Hawaiian waters-

&&

DISCUSSION...Kino
AVIATION...Vaughan
MARINE...Powell

Special Weather Statement
National Weather Service Honolulu HI
1034 AM HST Mon Dec 19 2022

HIZ006-007-009>011-032>036-192100-
Oahu North Shore HI-Ewa Plain HI-Koolau Windward HI-Waianae Coast HI-
East Honolulu HI-Waianae Mountains HI-Koolau Leeward HI-Olomana HI-
Honolulu Metro HI-Central Oahu HI-
1034 AM HST Mon Dec 19 2022

...Scattered strong thunderstorms will impact portions of Oahu
through 1100 AM HST...

At 1032 AM HST, Doppler radar was tracking scattered thunderstorms
over Oahu. The strongest storms were near Laie and near Pearl City,
moving east at 25 mph.

HAZARD...Wind gusts up to 55 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Honolulu, Waimanalo, Wahiawa, Waialua, Schofield Barracks, Hawaii
Kai, Ahuimanu, Punaluu, Wheeler Field, Kapolei, Waikele, Kalihi,
Barbers Point, Waiahole, Moanalua, Nanakuli, Pearl City, Waipahu,
Hauula and Mililani.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Severe Thunderstorm Watch remains in effect until 200 PM HST for
Hawaii.

&&

LAT...LON 2153 15784 2147 15784 2141 15778 2147 15777
      2147 15773 2141 15774 2131 15765 2126 15771
      2128 15771 2126 15782 2134 15790 2130 15791
      2134 15797 2130 15811 2149 15824 2153 15823
      2158 15828 2158 15812 2169 15803 2171 15797
TIME...MOT...LOC 2032Z 269DEG 21KT 2146 15789

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH

R Ballard

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
1132 AM HST MON DEC 19 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1118 AM     NON-TSTM WND DMG KANEOHE                 21.41N 157.79W
12/19/2022                   HONOLULU           HI   LAW ENFORCEMENT

            KAMEHAMEHA HWY CLOSED IN BOTH DIRECTIONS
            BETWEEN HAIKU RD AND HEEIA ST DUE TO LEANING
            POLES.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
1155 AM HST MON DEC 19 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0920 PM     FLASH FLOOD      WAIKOLOA VILLAGE        19.94N 155.79W
12/18/2022                   HAWAII             HI   EMERGENCY MNGR

            HI-190 CLOSED NEAR MILE MARKER 5-6, DEBRIS
            ON RD.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
1203 PM HST MON DEC 19 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0920 PM     FLASH FLOOD      KAWAIHAE                20.04N 155.83W
12/18/2022                   HAWAII             HI   EMERGENCY MNGR

            HI 270 CLOSED FROM MILE MARKER 10-11 DUE TO
            DEBRIS ON RD.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
1247 PM HST MON DEC 19 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1155 AM     TSTM WND DMG     WAIPAHU                 21.39N 158.01W
12/19/2022                   HONOLULU           HI   TRAINED SPOTTER

            SHINGLES BLOWN OFF ROOF. 40 MPH WIND.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
109 PM HST MON DEC 19 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1145 AM     TSTM WND DMG     1 E KAPOLEI             21.33N 158.05W
12/19/2022                   HONOLULU           HI   PUBLIC

            VIDEO SURFACED OF TREES DOWN IN THE KA
            MAKANA ALII SHOPPING CENTER PARKING LOT.

&&

GK