UCLA

An axisymmetric version of the Bryan Cloud Model (CM1) is used to determine how quickly a coherent and relatively stable tropical cyclone (TC) circulation can form from an initial vortex of nominal intensity. Some of the factors that may influence the onset time of the rapid intensification are examined, including the height of the tropopause, the microphysical parameterizations, the midlevel dryness and the total surface heat flux from the sea surface. Our analyses of these simulations suggest that there are two conditions that need to be satisfied before RI can occur: the vertical structure of the middle troposphere has to become moist adiabatic in the inner core and peripheral convection has to become suppressed or merged with convection in the inner region.