Extratropical Transition of Tropical Cyclones in a Changing Climate

The chapter discusses the transformation of tropical cyclones into extratropical storms in midlatitude baroclinic environments, a process known as extratropical transition (ET). During ET, storms typically decrease in maximum wind speed but increase in size, resulting in higher integrated kinetic energy. As such, the damage caused by ET can match or even exceed that caused by tropical cyclones. As the climate warms, tropical cyclones are expected to intensify and last longer. However, the accurate representation of ET events in climate models and their future projections in a changing climate remains a challenge. This chapter intends to (1) introduce the characteristics and a method for quantitatively measuring ET events, known as the cyclone-phase-space diagram, and (2) summarize the projections of high-resolution models in a warmer climate. In short, while there is no agreement among the models on the changes in the number of ET events in the North Atlantic, most models concur that the proportion and intensity of ET events will increase in the future, suggesting potentially stronger impacts of ET in a warmer climate.