Latidude 5 degrees or greater - minimum coriolis force required to initiate rotation of the system. Absence of wind shear with height. This will allow for unrestricted vertical development from the surface to the upper tropsphere. Upper level divergence greater than lower level convergence. Area of disturbed weather persists.
Thunderstorms begin to increase.
Thunderstorms release large amounts of latent heat due to condensation in the mid to upper troposphere. The increased pressure results in divergence of the air aloft. The total weight of the air is decreased which results in sea level pressure falling. The low leve winds converge and spin faster around the low pressure center as a result of the need to conserve angular momentum. As the winds converge towards the center they pick up warm water vapor from the ocean and the air rises as it releases more vapor and latent heat.