A site on the Hawaiian island of Kauai may have set a new US 24-hour rainfall record.
Hawaii is well known for heavy rainfall events but an astonishing 1-day rainfall event between April 14-15th may well have raised the bar of US extremes further.
Preliminary data suggests Waipa on the island of Kauai recorded 49.69 inches of rain within a 24-hour period. That’s the equivalent to a year’s worth of rain for Atlanta.
For further perspective, Hurricane Harvey last summer dumped over 60 inches within a 3-5 day period setting a new US storm total record but within a single 24 hours, while it was mighty impressive, it approached 30 inches, a far cry from what was seen in Hawaii this month.
A statement from the NWS Honolulu.
Preliminary data downloaded from a remote rain gage in North Kauai indicate that rainfall during the flash flood event on April 14-15, 2018 broke the U.S. 24-hour rainfall record. The rain gauge, located in Waipa about one mile west of Hanalei, recorded 49.69 inches of rainfall during the 24-hour period ending at 12:45 pm HST April 15. This total, if certified, will break the current U.S. 24-hour record of 43 inches at Alvin, TX on July 25-26, 1979, and the state of Hawaii record of 38 inches at Kilauea (Kauai) on January 24-25, 1956
Kauai is considered to be one of the wettest places on earth but 50 inches of rain within a day, well nowhere can handle that much, that fast and so widespread flash flooding resulted.
Via CNN: A US Coast Guard photo of flooding in Kauai’s Hanalei Bay.
Hawaii Governor David Ige surveys flood damage in Kauai on April 17, 2018.
Topography & wet/tropical climate create a near perfect example of orographic enhancement on precipitation
The steep mountainous rainforests which rise immediately from the sea on Kauai combined with an upper low drawing on rich tropical air triggered thunderstorms which anchored directly over the island making for a perfect place to maximise the orographic potential.
Interestingly the same site recorded 101 inches of rainfall in March 1942 and in 1982 more than 58 feet of rain fell that year, alone.
According to Chris C Burt, a weather historian at Weather Undergroud, the most impressive aspect to this record rain event is that it was not associated with a tropical cyclone.
Here is a list of other top 24-hour-rainfall records, all of which were related to a tropical storm or hurricane except for Waipa:
71.85 inches — Foc-Foc, La Reunion (Jan. 7-8, 1966)
66.49 inches — Belouve, La Reunion (Feb. 27-28, 1964)
64.33 inches — Isla Mujeres, Mexico (Oct. 21-22, 2005)
62.33 inches — Aurere, La Reunion (April 7-8, 1958)
55.20 inches — Weiliaoshan, Taiwan (Aug. 8, 2009)
55.04 inches — Commerson, La Reunion (Feb. 25, 2007)
51.85 inches — Kaikawa, Tokushima, Japan (Aug. 1, 2004)
49.69 inches — Waipa, Hawaii (April 14-15, 2018)** if certified
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