Severe Thunderstorm Warning 7, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
900 AM HST Thu Jan 30 2025

.SYNOPSIS...
A vigorous low pressure system passing by north of the state will
drag a cold front from northwest to southeast down the island
chain tonight and Friday. The storm system will bring the threat
for strong damaging south to southwest winds, severe thunderstorms,
and flash flooding along and ahead of the front today through
Friday. Conditions will gradually improve with cooler and drier
air building in behind the front Friday night through the weekend.
Cool and breezy trade wind weather is expected through the first
half of next week.

&&

.DISCUSSION...

A surface low will remain about 500 miles NW/N of Kauai for the next
12-18 hours as it slowly migrates east and deepens to 986mb, an
impressive feat for a winter system south of 30N. The attendant wind
field is deep and quite strong and is punctuated by a strong 55-60
positioned west of Kauai at press time. The strongly sheared wind
profile and surface-based instability characterized by 0-0.5km CAPE
around 1200 j/kg provides an extremely favorable parameter space for
organized convection, including supercells.

Today and tonight.
Current radar imagery supports as much as numerous elongated
supercells have been observed propagating to the NE over and
immediately east of Kauai in the Kauai Channel. These cells feature
organized and fairly long-lived rotational couplets capable of
producing tornadoes/waterspouts in addition to severe wind gusts and
potentially small hail, warm mid-levels generally being a limiting
factor for the latter. Further east, a plume of organized moist
isentropic ascent well in advance of the front is associated with
the influx of a high theta-e airmass supporting increasingly
widespread convection over Maui County. This convection is, so far,
less organized than that closer to the front/in the vicinity of Kauai
despite the presence of greater instability (1500-2000 j/kg),
perhaps owing to the more veered 0-3km bulk shear vector. If this is
indeed the case, the probability for supercells will decrease with
eastward extent through the day with the peak probability over Kauai
followed by Oahu and then a minimal threat for supercells over Maui
County. Here, the severe threat transitions to more of an exclusive
wind threat as deep convection capitalizes on the strong resident
wind field. The Severe Thunderstorm Watch in effect through noon
therefore remains in good shape through the near term. However, an
eventual extension in time and areal coverage to include Oahu and
potentially Maui County appears probable.

With that said, the primary threat remains intense, training bands
of showers and thunderstorms capable of producing flash flooding.
Coverage of heavy rain will increase statewide as the day
progresses. This will be mainly be associated with the cold front
and prefrontal convection over Kauai and with the aforementioned
influx of higher theta-e air/moist isentropic ascent for Oahu and
points east. The frontal rainband will gradually dissipate over or
in the vicinity of Kauai as dry air associated with the mid-level jet
punches in from the WNW. As this happens, convection will tend to
refocus over the eastern half of the state by late tonight into
Friday. Throughout this time, persistent southeast low-level flow
will focus increasingly heavy showers over the SE slopes of the Big
Island potentially well into Friday. The Flood Watch for the entire
state through Friday therefore remains in good shape.

Finally, the High Wind Warning for the entire state and winter
headlines for the summits of the Big Island remain in place as is
with no adjustments necessary at this time. The primary wind threat
outside of convection will be over and downwind of terrain,
particularly over northern and eastern portions of each island. The
greatest probability for damaging wind gusts will be over N and E
Kauai and Oahu followed by the remainder of the state. This threat
will persist through Friday, decreasing from west to east as the
front advances through the area.

Friday.
Moist southeast flow persists over the Big Island as a much drier
post-frontal airmass gradually eases over the remainder of the
state. Flooding potential therefore continues over the SE-facing and
kona slopes of the Big Island through much or all of Friday. The
latest high res guidance suggests some semblance of heavy rain
banding remaining established over the Big Island well into Friday
night. Any potential extension of the Flood Watch for the Big Island
would be evaluated tomorrow.

Saturday onward.
Dry post-frontal airmass characterized by dewpoints in the upper 50s
gradually filters into the area from the NW late Friday through
Saturday providing pleasantly dry weather as trade winds return,
particularly for Kauai through Molokai where dewpoints will be
lowest.

&&

.AVIATION...

An active weather pattern will continue across the state into
Friday morning as a deep low pressure system passes to the north.
A cold front approaches from the northwest, while multiple
convergence bands have set up over the main Hawaiian Islands late
this morning producing intense thunderstorms/lightning, localized
strong turbulence, reduced visibility and lowered ceilings,
and mountain obscurations.

SIGMET November is posted for thunderstorms for Kauai and
surrounding waters, along with much of the area distant north of
the state. A general eastward progression of the SIGMET is
expected today. AIRMET Sierra is posted beyond 2200Z for tempo
mountain obscurations above 1500 feet for the smaller islands
(entire island coverage) and above 2000 feet for the Big Island
(also the entire island).

AIRMET Tango is posted for tempo moderate turbulence below 10,000
feet, and also from FL270 to FL400 (entire state). Strong sustained
winds and downsloping gusts are expected along north and east
sides of the islands. Light icing is expected in layer 14,000 feet
to FL240 outside of the current SIGMET area.

The quickly evolving weather situation should be monitored today
and tonight. Check for AIRMET and SIGMET updates on our website
and on the Graphical Forecast for Aviation tool.

&&

.MARINE...

A strengthening 996mb low centered few hundred miles northwest of
Kauai will continue to move northeast and pass north of the
islands on Friday. Scattered severe thunderstorms have been seen
on radar with damaging winds and waterspouts over Kauai waters and
offshore waters. The threat for severe thunderstorms should
gradually shift eastward through the day and overnight tonight.
Special Marine Warnings have been ongoing over the coastal waters
due to the strong thunderstorms producing gusts above 50 kt. A
Gale Warning remains in effect for the waters around Kauai, and a
Small Craft Advisory is posted for the remaining coastal waters.
The Gale Warning for Offshore waters maybe upgraded to a Storm
Warning due to the deepening low pressure system.

Most of these weather hazards will occur in conjunction with
strong and gusty S to SW winds. However, a cold front trailing
south of this low center will also sweep from west to east
through the islands, bringing additional heavy showers and strong
thunderstorms along the frontal cloud band from tonight into
Saturday. Moderate to fresh W to NW winds with improving weather
trends will quickly build in after the front passes through each
island. The front should be pushing through the western half of
the state on Friday and the eastern half of the state Friday night
into Saturday. Moderate to locally strong NE trade winds will
develop by Sunday as high pressure builds far NW of the islands.

The declining mid-period NNW swell will be followed by a larger N
swell building in late this afternoon through Friday. The low passing
N of the state will continue to intensify as it moves away from the
island chain on Saturday and will produce moderate short-period
swells with a wide range of swell directions. Ranging anywhere from
the SW to NNE today through Saturday. A larger N to NNE swell is
possible Sunday into early next week and surf may reach advisory
thresholds. A couple moderate sized WNW swells are also expected, a
smaller one this weekend, and a slightly larger one from Monday into
Wednesday.

Rough and choppy surf, due to increasing short-period wind waves,
will develop along S and W facing shores from tonight through
Friday due to the increasingly strong low-level S to SW winds.

&&

.FIRE WEATHER...
Critical fire behavior conditions are not expected during the
forecast period.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Friday afternoon for Niihau-Kauai Leeward-
Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central
Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West-
Maui Leeward West-Haleakala Summit-Kona-Kohala-Big Island
Interior-Kauai North-Kauai East-Kauai South-East Honolulu-
Honolulu Metro-Ewa Plain-Koolau Windward-Koolau Leeward-Molokai-
Lanai Windward-Lanai Leeward-Lanai South-Maui Central Valley
North-Maui Central Valley South-Windward Haleakala-Kipahulu-
South Maui/Upcountry-South Haleakala-Big Island South-Big Island
Southeast-Big Island East-Big Island North.

High Wind Warning until noon HST Friday for Niihau-Kauai Leeward-
Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central
Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West-
Maui Leeward West-Kona-Kohala-Big Island Interior-Kauai North-
Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-
Koolau Windward-Koolau Leeward-Molokai-Lanai Windward-Lanai
Leeward-Lanai South-Maui Central Valley North-Maui Central
Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry-
South Haleakala-Big Island South-Big Island Southeast-Big Island
East-Big Island North.

High Wind Warning until 6 PM HST Friday for Haleakala Summit.

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

Winter Storm Warning from noon today to 6 AM HST Saturday for
Big Island Summits.

Gale Warning until 6 AM HST Friday for Kauai Northwest Waters-
Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel.

Small Craft Advisory until 6 AM HST Friday for Oahu Windward
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...JVC
AVIATION...Foster
MARINE...Kino
FIRE WEATHER...JVC

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Special Weather Statement
National Weather Service Honolulu HI
214 PM HST Thu Jan 30 2025

HIZ003-029-310045-
Kauai North HI-Kauai Southwest HI-
214 PM HST Thu Jan 30 2025

...A STRONG THUNDERSTORM WILL IMPACT KAUAI IN KAUAI COUNTY THROUGH
245 PM HST...

At 212 PM HST, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Barking Sands, or 31 miles west of Lihue, moving
northeast at 40 mph. This thunderstorm will move near Barking Sands
and Kekaha at approximately 230 PM HST.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Kekaha, Mana, Waimea, Barking Sands, Polihale, Pakala Village, and
Waimea Canyon State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2196 15957 2192 15964 2196 15967 2199 15977
      2202 15979 2206 15979 2211 15974 2214 15973
TIME...MOT...LOC 0012Z 237DEG 36KT 2194 15985

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

Wroe

Preliminary Local Storm Report
National Weather Service Honolulu HI
227 PM HST Thu Jan 30 2025

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

0141 PM     Non-Tstm Wnd Dmg 4 WNW Hilo              19.72N 155.14W
01/30/2025                   Hawaii             HI   Public

            Waianuenue Avenue in South Puna is closed in
            Piihonua (above bridge) due to down trees
            and fallen power lines.

&&

MMB