Tropical cyclones in vertical shear: An idealized study of TS Chantal (2001) during the CAMEX-4 field campaign

Abstract

Recent observational and idealized modeling studies of tropical cyclones (TC) in environmental vertical wind shear have shown that the storms tend to have strong and persistent wave number one asymmetries, particularly in the rainfall and vertical velocity fields. The asymmetries in the tropical cyclone structure that develop under the influence of westerly wind shear have been shown to be significantly greater compared with those that develop under similar easterly shear strength. The intensity of the tropical cyclone is similarly impacted, with a TC in westerly shear being significantly weakened compared with a TC in easterly shear of the same magnitude. Tropical storm Chantal (2001) developed in strong and persistent westerly shear during the NASA CAMEX-4 field campaign in conjunction with the Hurricane Landfall (HL 2001) experiment. Whereas the storm struggled to develop throughout its lifetime, periods of strengthening and weakening can be directly related to the amount of vertical wind shear present in the environment. Using idealized model simulations that resemble the environment sampled by the NASA DC-8, ER-2 and NOAA P3 aircraft during Chantal’s struggle for survival, the relationships among the environmental vertical wind shear and the tropical cyclone wind and precipitation structure, and specifically the tropical cyclone intensity, will be examined.