2020 年 15 巻 6 号 p. 726-734
In August 2017, Hurricane Harvey brought an unprecedented amount of rainfall and catastrophic flooding to the Houston metropolitan area, as it stalled near the coast of Texas for several days after weakening to a tropical storm intensity. The present study examines the relationship between tropical cyclone rainfall totals over Texas and the track, residence time, rainfall intensity, and rainfall area coverage of past tropical cyclones that approached Texas after 1979. The most significant factor affecting rainfall totals over Texas is whether a tropical cyclone makes landfall on the central coast of Texas and travel inland. Another significant factor is the length of time a tropical cyclone resides near Texas. Rainfall intensity also contributes in part to rainfall totals over Texas, whereas contribution of rainfall area coverage is not significant. The track of a tropical cyclone traveling near Texas is controlled by the steering winds over Texas, while its residence time near Texas is related partly to the meandering of the subtropical jets. Rainfall rate depends on the intensity of tropical cyclone. No significant relationship between rainfall intensity and environmental moisture in the lower atmosphere is found in the present analysis. Furthermore, the extreme rainfall totals over Texas induced by Harvey can be attributed to the combined effect of extreme long-term stalling of Harvey near the central coast of Texas and the higher rainfall rate.