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Tropical Cyclone Development

There are five conditions that must be present for a tropical system to develop and intensify.

1. Warm sea surface temperature - 26.5 degrees C (80 degrees F) or greater.
      This is needed for a constant supply of water vapor for the release of latent heat of condensation.

2. Latitude 5 degrees or greater - minimum coriolis force required to initiate rotation of the system.

3. Absence of wind shear with height - this will allow for unrestricted vertical development from the surface to the upper tropsphere.

4. Upper level divergence greater than lower level convergence - needed for a strong flow of winds coming in at the surface.

5. Pre-existing low-level disturbance

If the area of disturbed weather persists:

1) Thunderstorms begin to increase.

2) Thunderstorms release large amounts of latent heat due to condensation in the mid to upper troposphere.

3) This warming results in increased pressure aloft.

4) The increased pressure results in divergence of the air aloft.

5) The total weight of this column of air is decreased, which results in sea level pressure falling.

6) The low level winds converge and spin faster around the low pressure center as a result of the need to conserve angular momentum.

7) As the winds converge towards the center, they pick up warm water vapor from the ocean. The air rises as it releases more vapor and latent heat.

8) The center grows warmer which results in more divergence aloft.

9) Air at the outer edges is dragged upward and outward by the surrounding air. The air above sinks into eye.