On the Role of Coriolis Forcing in the Bifurcation of Tropical Cyclone Development

Tropical cyclones (TCs) are well documented to be dominantly cyclonic (anticyclonic) in the Northern (Southern) Hemisphere. One key mechanism for this asymmetry in TC circulation is often attributed to the Coriolis moment torque that helps spinup the TC circulation in one specific direction in each hemisphere. Using the TC-scale framework recently developed by Kieu (2015), we will prove that the Coriolis force plays a secondary role in the rapid spinup of TC rotational wind. Instead, the Coriolis force acts as a bifurcation parameter that breaks the symmetry of the TC development and results in a larger basin of attraction toward the cyclonic (anticyclonic) stable point in the Northern (Southern) Hemisphere. Our finding offers a new insight into the role of the Coriolis force in TC development, and helps explain the preference of TC rotational flow in each hemisphere.