A low pressure trough moving slowly westward through the northwestern Hawaiian Islands caused destructive flooding and mudslides over the past weekend. The trough disrupted the normal northeast trade winds flow north of Oahu on April 12, 2018. This caused extremely heavy rainfall as the trough deepened and moved very slowly over Kauai during the weekend. The 28.1 inches (713 mm) of rain reported in Hanalei within a 24 hour period was close to a record for the small town on Kauai's northern coast. Almost 32.4 inches (822 mm) of rain was reported during the same period over Wainiha, Kauai.
It is sunny in southern California today but recent unusually heavy rainfall led to rock slides, mudslides and flooding in that part of the country. Rainfall of almost 4 inches (101.6 mm) in one day was reported in Long Beach, California. Some highways in the area were flooded due to intense downpours. Rainfall since the fall of 2016 has improved drought conditions over northern California but Southern California has been slower to improve because of the exceptional rainfall deficit in that area.