An unstable atmosphere in addition to abundant moisture allowed persistent heavy rain to develop over the Big Island Kona slopes. This heavy rainfall led to flash flooding with multiple properties reportedly flooded.
Every event with a place to put it. 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.
An unstable atmosphere in addition to abundant moisture allowed persistent heavy rain to develop over the Big Island Kona slopes. This heavy rainfall led to flash flooding with multiple properties reportedly flooded.
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 18, 10:00 AM HST, 4 hours earlier.
Area Forecast Discussion National Weather Service Honolulu HI 1000 AM HST Wed Sep 18 2024 .SYNOPSIS... Gentle to breezy trade winds will prevail the next several days. A drier statewide weather pattern will occur through the remainder of the week. Occasional showers will mainly focus along higher windward terrain with more frequent overnight shower activity. Areal rainfall may pick up early next week as an upper low north of the state comes in close proximity of the islands. && .DISCUSSION... A 1030 mb high centered approximately 1,000 miles north of Hawaii is producing a tight enough pressure gradient back toward the state to maintain statewide gentle to breezy trade winds. Little movement nor weakening of this high the next couple of days guarantees similar trade behavior through Thursday. While the high will subtly weaken and shift east from Friday into the weekend, overall winds will remain at gentle to breezy magnitudes into early next week. Thus, diurnal precipitation behavior will be of a trade nature...mainly windward and upper terrain shower activity with more frequent overnight showers. The same climate caveats will also apply such as increased afternoon cloud cover and rain over Big Island Kona and occasional morning leeward side sprinkles. A drier mid-level air mass advecting across the islands the next few days has the forecast trending on the drier side of traditional trade flow climate. There is potential change to the regional weather pattern this weekend as a couple of upper lows (or weak troughs) northwest and northeast of the state consolidate and descend south toward the area. While numerical guidance is out of phase with this regional lowering of heights, a signal has been noted and this will likely equate to a transition to a more wet pattern by early next week. As upper heights begin to fall this weekend, mid to upper levels will cool and moisten. The question will be how the synoptic shapes up concerning the 'when' and 'how long' of increased statewide precipitation. Hence, the current forecast will lean toward a more wet forecast next Sunday through the middle of the week in relation to these lowering heights from a potential upper low forming over or near the islands. && .AVIATION... Moderate to breezy trade wind flow will prevail for the next couple of days. Stable conditions will result in only limited areas of low ceilings and temporary MVFR conditions over windward and mountain locations. Aside from afternoon clouds over Kona slopes of the Big Island, VFR conditions should prevail for most locations. AIRMET Tango remains in effect for low-level turbulence over and downwind of island terrain. This AIRMET will likely remain in effect at least for the next couple of days. && .MARINE... High pressure north northeast of the Islands will keep moderate to locally strong trade winds in place through the weekend. A slight weakening of the high could decrease wind speeds early next week. A Small Craft Advisory (SCA) is now in effect for the typically windy waters around Maui and the Big Island through 6 AM Friday. The SCA may eventually need to be extended through the weekend. East shore surf will hold near seasonal levels through Thursday, then slowly lower Friday through early next week. A mix of southeast, south and southwest swells will keep small surf in place for south facing shores through Monday. A slight bump in south shore surf is possible around Tuesday or Wednesday of next week as a slightly larger long-period southwest swell arrives. North shore surf will remain very small through the weekend until Tuesday and Wednesday of next week when a 3 to 5 foot medium to long- period northwest swell could arrive. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Friday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && DISCUSSION...Blood AVIATION...Vaughan MARINE...Birchard/Tsamous
The Kamuela/Kohala Apt radar (PHKM), 59 km away, was scanning. The volume nearest the first event began at 00:03 UTC.
1 flash flood. Local standard time, as filed.
Hualalai Rd was closed near Lako St due to flooding. Twenty two properties reported flood damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Hawaii in 2024Every state in 2024This day in weather historyWarnings in Hawaii, September 2024
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: 1208019.