Observing equipment reported gusts as high as 39-48 kts which uprooted some trees, knocked out power, and displaced shingles.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS HFO wrote it up.
Observing equipment reported gusts as high as 39-48 kts which uprooted some trees, knocked out power, and displaced shingles.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Honolulu, HI wrote its last area forecast discussion before the first event at Apr 18, 8:55 PM HST, 2 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service Honolulu HI 855 PM HST Tue Apr 18 2023 .SYNOPSIS... A cold front and convective shower band are moving into the islands from the northwest bringing widespread rainfall to the state. Threats for heavy rain, flooding and thunderstorms are expected mainly along and ahead of the frontal band affecting Kauai through the overnight hours, Oahu through Wednesday morning, reaching the islands in Maui County and the Big Island from Wednesday to Thursday. More stable conditions with westerly winds will fill in rapidly behind the front for the western half of the state by Thursday. East to southeasterly winds will develop across the region on Friday with isolated scattered showers forecast into early next week as a weak cold front approaches the islands from the northwest. && .DISCUSSION... The evening water vapor satellite imagery shows a diverging jet stream over the islands with deep convective showers developing along and ahead of a cold front drifting slowly eastward through the Kauai Channel and Oahu. Heavy showers are embedded along this cold front with isolated thunderstorms. Local radar on Kauai shows strong winds aloft that will support localized wind gusts up to 40 MPH in some of the heaviest convective showers. So far this evening most of these heavier showers are moving through the Kauai channel, however these heavier showers and potential thunderstorms will affect Oahu as the convective band moves over the island later tonight. Higher 3 hour rainfall totals as this convective band moved through Kauai earlier this evening ranged from 0.50 to 1.35 inches. Expect brief periods of heavy rain for Oahu through Wednesday morning with higher rainfall amounts of around 1 to 2 inches possible. This weather pattern features a combination of unstable southerly winds, surface convergence along and ahead of the cold front, upper level divergence, and moderate wind shear. These condition will produce and unstable environment along and ahead of the cold front as it marches eastward across the state through Thursday. Periods of moderate to heavy rainfall are expected to affect all islands with isolated to scattered thunderstorms. Southerly winds will tend to force moisture and showers over mountain slopes along the southern sides of each island where some of the higher rainfall amounts are forecast. The strongest wind gusts ahead of the front will favor the down wind northern slopes of any island mountains. Southeasterly winds currently over the Big Island are also producing a band of persistent moderate rainfall along southeastern slopes with higher rainfall amounts over the typically drier areas of the Ka'u and Puna Districts this evening. A Flood Watch remains in effect for all islands through Wednesday afternoon to account for these elevated flash flooding threats. This Flood Watch may need to be extended into Thursday morning for the Big Island due to the extended timing of the cold frontal passage. This Flood Watch coverage will likely be trimmed back from west to east on Wednesday as the cold front passes through each island and more stable conditions behind the front cause the flooding threat to diminish. More stable conditions will develop rapidly behind the front as it passes through the western islands on Wednesday. Winds will veer from a more westerly direction with drier conditions and decreasing shower activity spreading from west to east. Weather conditions will likely improve over Kauai and Niihau by sunrise Wednesday morning, and over Oahu by Wednesday afternoon. The frontal band will weaken as it passes through each island as the front stalls and dissipates near Maui and the Big Island on Thursday. A high pressure ridge will then build in from the northeast, briefly strengthening the trade winds, and pushing lingering showers back westward across Molokai, Oahu, Kauai and Niihau on Friday and Saturday. East to southeast winds return later this weekend as another cold front approaches the islands from the northwest weakening the ridge north of the island chain. && .AVIATION... A front currently near Kauai will move to Oahu late tonight and then to Maui County Wednesday. The most common impact to aviation will be widespread MVFR CIG/VIS in showers, with isolated IFR CIG/VIS in heavier showers. AIRMET Sierra for mountain obscuration continues on Kauai, and SE Big Island, and will remain in place through at least the first half of the night. The front will also bring a threat of isolated thunderstorms. Moderate to locally strong SE to S winds will increase ahead of the front, supporting SIGMET Tango for low to mid level turbulence from Kauai to Maui tonight. In addition, MODERATE icing may be encountered in layered clouds along and just E of the front. VFR conditions have prevailed over most areas east of Kauai through this evening, but expect deteriorating conditions on Oahu as early as this evening, with widespread MVFR and mountain obscuration expected later tonight. As Kauai experiences clearing Wednesday morning, the front will likely be impacting Maui County. On the Big Island, MVFR conditions have been confined to southeast facing slopes but should be more extensive Wednesday afternoon. && .MARINE... Latest radar imagery shows a band of moderate to heavy showers centered over the Kauai Channel from the southwest to the northeast that has embedded cells capable of producing gusts 34 kt or greater. This band of showers is associated with an advancing cold front that will move over Kauai tonight before moving eastward across Oahu and the central smaller islands Wednesday, then weakening and stalling across the eastern end of the state Thursday. Fresh to strong south winds associated with the front will continue across Kauai and Oahu this evening, before expanding eastward across the remainder of the islands tonight through Wednesday as the front advances down the island chain. Seas will respond quickly and become rough over exposed waters, especially in and around heavy showers and thunderstorms that develop along and ahead of the front. Thunderstorms continue over the offshore waters (around 90 nm northwest of Kauai) in advance of the approaching front. The showers and storms will continue for Kauai waters this evening, then Oahu and Maui County waters tonight. Winds and seas will quickly drop off on the backside of the exiting front Wednesday, first for Kauai and Oahu waters early Wednesday afternoon, then Wednesday evening near Big Island. Winds will become north to northeast Thursday through Friday for all waters as weak high pressure builds to the north. The Small Craft Advisory includes all waters, excluding Big Island southeast waters through Wednesday afternoon, however some zones may be dropped earlier as conditions relax behind the front. Surf along north and west facing shores will pick up late Wednesday as a small to moderate west-northwest medium period swell arrives from low pressure centered over 800 nm to the northwest. This source will peak Thursday, then ease Friday. A long-period northwest swell from a distant source in the far northwest Pacific is forecast to arrive Friday night, build through the day Saturday, then peak Saturday night into Sunday before easing. Surf along south facing shores will become rough and choppy through Wednesday due to the aforementioned strong south winds associated with the cold front moving through. This will quickly lower by Thursday as the winds ease. A long-period south swell associated with a typical system passing through our swell window in the southern Pacific will arrive Friday night, then peak over the weekend. Surf along east facing shores will remain small through the week due to the lack of trades locally and upstream. && .HFO WATCHES/WARNINGS/ADVISORIES... Flood Watch through Wednesday afternoon for all Hawaiian Islands. Small Craft Advisory until 6 PM HST Wednesday for most coastal waters and channels. && DISCUSSION...Bohlin AVIATION...Birchard MARINE...Almanza
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
1051 PM HST TUE APR 18 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1041 PM FLASH FLOOD KAWA FLATS 19.13N 155.53W
04/18/2023 HAWAII HI EMERGENCY MNGR
EMERGENCY MANAGEMENT REPORTED HIGHWAY 11
NEAR KAWA FLATS BETWEEN MILE MARKER 50.5 AND
MILE MARKER 60 WAS CLOSED DUE TO WATER OVER
THE ROAD.
&&
JRJSpecial Weather Statement
National Weather Service Honolulu HI
1057 PM HST Tue Apr 18 2023
HIZ006-007-009>011-032>036-191030-
Oahu North Shore HI-Ewa Plain HI-Koolau Windward HI-Waianae Coast HI-
East Honolulu HI-Koolau Leeward HI-Waianae Mountains HI-Olomana HI-
Honolulu Metro HI-Central Oahu HI-
1057 PM HST Tue Apr 18 2023
...Strong thunderstorms will impact portions of Oahu in Honolulu
County through 1230 AM HST...
At 1056 PM HST, Doppler radar was tracking strong showers along a
line extending from 24 miles west of Waianae to 15 miles south of
Barbers Point. Movement was northeast at 35 mph.
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...
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.
&&
LAT...LON 2153 15784 2147 15784 2141 15778 2147 15777
2147 15773 2141 15774 2131 15765 2126 15770
2130 15772 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 0856Z 234DEG 30KT 2132 15854 2109 15803
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
JelsemaThe national radar mosaic for the moment the first event began.
4 strong wind. Local standard time, as filed.
There was a fallen tree that closed the Pali Highway in the Honolulu bound direction from Kamehameha Highway.
The public reported that shingles were blown off and minor tree damage occurred due to the strong winds.
The utility company reported 24,000 customers without power on the island of Oahu due to strong winds.
An NWS employee reported an uprooted tree in their yard.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Hawaii in 2023Every state in 2023This day in weather historyWarnings in Hawaii, April 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1092675, 1092677, 1092676, 1092679.