Downpours occurred over a portion of leeward Haleakala in East Maui with afternoon heating, leading to flash flooding on the 9th. More showers developed later over parts of Oahu, Maui, and the Big Island.
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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.
Downpours occurred over a portion of leeward Haleakala in East Maui with afternoon heating, leading to flash flooding on the 9th. More showers developed later over parts of Oahu, Maui, and the Big Island. No serious injuries or property damage were reported.
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 Sep 9, 10:00 AM HST, 3 hours 26 minutes earlier.
Area Forecast Discussion National Weather Service Honolulu HI 1000 AM HST Fri Sep 9 2022 .SYNOPSIS... Moderate trade winds will weaken through Saturday, remain on the lighter side through the weekend, then increase again early next week. An area of increased moisture will bring clouds and showers to mainly windward portions of the islands from Kauai to Maui into tonight, with fewer showers Saturday and Sunday. However, the light winds this weekend may allow some afternoon showers to develop over leeward areas, with clearing at night. An increase in showers is expected over the Big Island on Monday. && .DISCUSSION... An area of increased low-level moisture embedded within a moderate trade wind flow continues to spread clouds and showers to the islands from Maui to Kauai, largely bypassing the Big Island, where skies are mostly sunny. Additionally, a developing trough aloft N of Kauai has weakened and elevated the subsidence inversion, and latest radar data indicates moisture extends as high as 14000', which has allowed some of the showers to become briefly, although they are not remaining over any one area for particularly long. We have received several rainfall alarms this morning from gages in windward Kauai and Oahu, with rainfall rates near 1 inch/hour observed. Although we might normally expect some diurnal decrease in shower coverage this afternoon, model guidance indicates weak low-level convergence helping to support showery weather from Maui to Kauai into tonight before moving W of the islands early Saturday. Weak surface high pressure to the distant NE will dissipate tomorrow, while a new high develops far N of the islands this weekend. This new high will move slowly S toward the islands early next week while gradually weakening. This will cause to trade winds to gradually diminish through Saturday, then slowly strengthen Sunday into next week. The gentle trade winds will remain strong enough to bring showers to windward areas, especially during nights and mornings, but will also be sufficiently light to allow land and sea breezes over leeward areas. After the current field of moisture clears the islands to the W on Saturday, some lingering low-level moisture and weak instability associated with the trough aloft N of Kauai will help support some shower development, especially over Kauai and Oahu. Global models continue to show a significant northward surge of tropical moisture approaching the Big Island from the S, although the timing has trended a little earlier, with PWAT increasing Sunday night and Monday. Although this moisture field will likely be weakening as it approaches, it looks as if it will bring an increase in showers to the Big Island on Monday, especially windward. Forecast grids will be modified to account for this change in forecast philosophy. Moderate trade winds for the first part of next week may trend weaker over the second half, and a nearby weak NE-SW oriented low-level trough may bring an increase in showers around midweek. && .AVIATION... Deeper low level moisture advecting into the islands from the east has enhanced windward shower activity and cloud coverage. Periodic MVFR ceilings and visibilities will continue through the rest of the morning. AIRMET Sierra remains in effect for tempo mountain obscuration for Maui, Molokai, Oahu, and Kauai, and will likely remain in effect through midday. Light to locally moderate trade winds will continue to gradually weaken through Saturday as surface high pressure far northeast of the state dissipates and is replaced by another high that will slowly move towards the islands early next week. The result will be light to locally moderate trades remaining strong enough to focus showers and clouds across windward locations (especially during the overnight through early morning hours), but weak enough to allow nighttime land breezes and afternoon sea breezes for some leeward locations. && .MARINE... Gentle to moderate east trade winds will generally remain in place through this weekend as high pressure far off to the northeast of the state weakens and relaxes the gradient down upon the islands. Lighter winds equate to just land and sea breezes along and near the coasts through Sunday. Moderate to fresh trade winds will return Monday and then hold through mid week. The incoming south southwest swell will increase surf along south- facing shores through the day Saturday, peaking out near surf advisory levels late Sunday through Monday, then slowly fall through mid week. A medium period southeast swell arriving Monday will be added to the mix and will hang on through Wednesday. Surf along east- facing shores will ease into the weekend as trades back off, but may come up Sunday if a medium period easterly swell from former East Pacific Hurricane Kay reaches our east shores. Choppy east wind wave surf surf will pick up next week in response to strengthening trades. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && DISCUSSION...Birchard AVIATION...TS MARINE...Blood
The Molokai radar (PHMO), 88 km away, was scanning. The volume nearest the first event began at 23:24 UTC.
6 heavy rain, 1 flash flood. Local standard time, as filed.
Flooding forced the closure of South Kihei Road at Kalani Road in Kihei on Maui. More inundation was reported near Kalama Park in the area of Waimahaihai Street and Keala Place.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Hawaii in 2022Every state in 2022This day in weather historyWarnings in Hawaii, September 2022
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: 1051091, 1051097, 1051098, 1051100, 1051101, 1051103, 1051104.