Severe flooding in Oahu, Hawaii, is the product of an unusually potent and persistent Kona Low. The latter is a center of low pressure that typically develops northwest of the Hawaiian Islands during the winter months, sweeping tropical moisture across that archipelago from the southwest.
Held in place by an atmospheric trough (a dip in the jet stream), this "cutoff low"generally persists for a few weeks, producing a typical rainy season. This year, the Kona Low developed relatively late in the winter but its strength and persistence has led to the torrential precipitation and record flooding.
Of interest, this atmospheric trough over the Pacific is tied to the persistent atmospheric ridge over the Desert Southwest, which has fueled the severe heat that is currently spreading eastward across the U.S. Climatologists believe that both extremes demonstrate the effects of our warming climate.
