As a front approached the Aloha State with upper air support, an area of showers formed to the south of Oahu and began training over the isle. The showers became intense and isolated thunderstorms also developed.
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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.
As a front approached the Aloha State with upper air support, an area of showers formed to the south of Oahu and began training over the isle. The showers became intense and isolated thunderstorms also developed. The deluge led to flash flooding conditions. However, no significant injuries were reported. The costs of any damages were not available.
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 Dec 26, 9:55 AM HST, 6 hours 5 minutes earlier.
Area Forecast Discussion National Weather Service Honolulu HI 955 AM HST Tue Dec 26 2017 .SYNOPSIS... Showers and thunderstorms ahead of an approaching front will impact the smaller islands today and tonight. A cold front will shift eastward across the state Wednesday and Wednesday night, bringing improving conditions and a decrease in showers in its wake. Trade winds along with drier and more stable conditions will begin to return on Thursday, with locally breezy trade wind weather feature mainly windward and mauka showers then expected through early next week. && .DISCUSSION... A 1006 mb closed surface low is located 425 miles northwest of Kauai moving east at 25 mph, and dragging a cold front towards the state. Far to the northeast of Hawaii, a a nearly stationary 1026 mb high is centered. These two features are driving gentle to moderate south to southeasterly winds over the state, which is expected to bring an increase in moisture over the islands today. Visible satellite imagery shows cloudy skies across Kauai and Oahu and mostly sunny skies over Maui County and the Big Island. Radar loop through the morning shows heavy showers with some embedded thunderstorms over and around Kauai and Oahu. Water vapor imagery and satellite derived upper level winds indicate an upper level trough associated with the surface low with an axis 225 miles west of Kauai this morning. There is a potential for strong to possibly severe thunderstorms in association with today's storm system. Increasing moisture in combination with strong forcing for ascent provided by the upper level trough, is expected to lead to thunderstorm development across the western and central islands through tonight. Although conditions are not as ominous as the models depicted 24 hours ago, ingredients still remain favorable for organized convection over the western and central islands. Surface based CAPE values are expected to climb into the 1000 to 1500 J/KG range today, with 700 mb to 500 mb lapse rates of 6.5 to 7.0 C/km, and 0-6 km bulk shear values of 30 to 40 knots. As a result, we expect increasing thunderstorm development continuing through tonight as the deepest moisture and strongest forcing for ascent most closely align. Some of the thunderstorms may be strong and possibly severe from Kauai to Maui County. The main hazards from the strongest storms that move through the area are expected to be straight line damaging winds and hail. Some locally heavy rainfall will be possible with the thunderstorms as they move through the area as well, but given the strong deep layer flow, the thunderstorms should be progressive and not linger in any particular location for an extended period of time. As a result, flash flooding is not anticipated. Additionally, University of Hawaii's Vog Model shows the plume from Kilauea remaining over the smaller islands today, resulting in hazy conditions. Vog will decrease over Kauai and Oahu tonight as showers scour out some of the vog and the flow turns more southwesterly. The southwesterlies are then expected to pull the vog plume off of Maui by daybreak Wednesday, but it will continue to affect windward Big Island through at least Wednesday night. Winds are expected to be advisory levels over the Big Island summits through tonight due to the enhanced wind aloft caused by the upper trough. A Wind Advisory is now in effect. The earlier mentioned surface low will track north of the state tonight and Wednesday and drag the front across the island chain Wednesday and Wednesday night. A trailing band of clouds and showers associated with the front, along with another shortwave trough moving overhead, will keep conditions somewhat unsettled, particularly from Oahu eastward to the Big Island. Thursday through next Tuesday, More settled weather will overspread the island chain as high pressure builds in to the north of the state, and the cold front continues to shift eastward and away from the area. Moderate north-northeasterly winds are expected behind the front, with moderate trades then returning Friday through early next week. More typical trade wind weather is expected statewide, with showers favoring windward and mauka areas through the period. && .AVIATION... A cold front northwest of the state will continue to advance towards Kauai today. Winds have veered out of the southeast and south for most of the state. Kauai and Oahu will continue to see prefrontal effects, from periods of heavy showers, lower visibilities, and a chance of thunderstorms through the day and into tonight. Any thunderstorm can bring periods of IFR CIGS/VIS, lightning, and turbulence. There is also a possibility of small hail. AIRMET SIERRA for mountain obscuration is posted for Kauai and Oahu. PHJR and PHNL will be susceptible to prolonged periods of MVFR CIGS/VIS to isol IFR as showers fill in from the south. Any layered clouds around Kauai and Oahu also pose the threat for isolated light icing. The most significant upper level support looks to reach the western islands this afternoon and evening. Conditions will then start to improve after midnight for Kauai. Tempo MVFR CIGS/VIS are likely on Molokai and Lanai through this afternoon, before the threat of thunderstorms spreads east this evening. AIRMET SIERRA will be expanded as needed today. Maui and the Big Island should see predominately VFR conditions today, with showers and possible thunderstorms spreading to Maui late tonight. && .MARINE... Winds over the coastal waters have been veering from the southeast to south as a low northwest of the area tracks to the east. A front associated with the low will affecting at least the western half of the state through tonight. The feature will bring widespread showers and periods of thunderstorms to much of the area, which may include lightning, low visibilities, and strong and gusty winds. A reinforcing north-northwest swell is turning more northerly. Therefore, surf along east facing shores with a more northern exposure will likely see elevated surf for the smaller islands, and later this morning for the Big Island. A High Surf Advisory (HSA) is posted for east facing shores of Kauai, Oahu, Maui, Molokai, and the Big Island through this afternoon. The low mentioned above is forecast to move to a position north of the state around Wednesday. Model runs have backed off a bit on the strength of the winds in the fetch directed at the islands. Thus, surf is now expected to stay just below HSA criteria for north facing shores. An HSA for the exposed east facing shores would become more likely. The swell, however, is highly dependent on the position and strength of the low. Most south facing shores should see a slight bump in surf this week from a series of small long-period south-southwest and southwest swells. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until 6 PM HST this evening for east facing shores of Niihau, Kauai, Oahu, Molokai, Maui, and the Big Island. Wind Advisory until 6 AM HST Wednesday for Big Island Summits. && DISCUSSION...Foster AVIATION...Eaton MARINE...TS
The Molokai radar (PHMO), 68 km away, was scanning. The volume nearest the first event began at 02:00 UTC.
1 flash flood, 1 heavy rain. Local standard time, as filed.
Off-duty NWS employee reported water flowing into stores at Market City near Kaimuki Avenue and Kapiolani Boulevard in Honolulu.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Hawaii in 2017Every state in 2017This day in weather historyWarnings in Hawaii, December 2017
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: 727116, 727117.