A new U.S. weather record has been recently certified by the National Climate Data Center's Extremes Committee. In a 24-hour period from April 14-15, 2018, an incredible 49.69 inches of rain was recorded at Waipa Garden, Kauai! This deluge of over 4 feet of rain in one day breaks the old 24-hour U.S. rainfall record of 43 inches, which was set on July 25-26, 1979 in Alvin, Texas.
Unlike the 1979 Alvin, Texas event, which was tied to Tropical Storm Claudette, the 2018 Hawaii record event wasn't a result of any organized tropical cyclone. Instead, a trough of low pressure extending from near and just to the west of the Hawaiian Islands worked in conjunction with enhanced moisture embedded within the low level trade winds to produce the unprecedented deluge.
Radar data from the event shows an intense band of thunderstorm activity setting up over the northern coast of Kauai and becoming nearly stationary for several hours. Rainfall rates under the most intense portion of this convection ranged from 5 to 7+ inches per hour.
This unprecedented rainfall resulted in damage to 532 homes in both Kauai and Oahu for a damage cost of nearly $20 million, just for public property alone. 15 separate landslides blocked Kuhio highway and disrupted relief efforts for weeks after the event.