19 Influence of Convergence of Angular Momentum on Eyewall Replacement Cycle

Tuesday, 17 April 2018
Champions DEFGH (Sawgrass Marriott)
Sweta Das, Florida State Univ., Tallahassee, FL; and D. T. N. Krishnamurti

This study is to test two ideas during the formative process during the eye wall replacement cycle (ERC) of a hurricane. It is recognized that ERC has many flavors. Our hypothesis, that we test here, has two ingredients, one is that when the outer rain band of a hurricane encircles a large arc around it shuts off the supply of angular momentum to the parent hurricane thus weakening it. Streamlines of storm relative flow cease to cross the encircling arc cloud and the transport of outer angular momentum weakens. The accumulation and convergence of flux of angular momentum strengthens the azimuthal flows around the outer arc cloud. During this time we also examine the energy exchanges among the divergent and rotational kinetic energy in the present cyclone and the new outer arc as it contributes to the ERC. We note that the parent eyewall undergoes a large transformation of rotational kinetic energy into divergent kinetic energy and the converse is noted at the outer arc cloud as the ERC ensues. There are two possibilities for the initiation of the ERC, one that it all starts from the storm environment, outside the inner core and the second is it has to do with a disruption of the organization of convection of the parent vortex, emanating in the inner core. We examine these two possibilities. To understand the role of angular momentum convergence and energy conversion on the mechanism of ERCs hurricanes are categorized in two different sections: a) ERC with rapid intensification and b) ERC with no rapid intensification. For this purpose hurricane Matthew, Edouard and Irma has been considered.
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