text: what is a tropical disturbance?   a tropical disturbance is not often associated with a surface low.  so it is not a tropical cyclone. (in the atlantic basin) as tropical waves exit the coast of africa, the associated thunderstorms are fueled by warm ocean waters.  this means a large area of convection develops.  again, there is no surface low, so it is not a tropical cyclone. storms continue to grow, usually in a pulse type pattern.  daytime heating will allow numerous storms to fire, then the convection settles down a bit at night. once the system has full tropical characteristics, and a surface low pressure.... it is considered a tropical cyclone (depression/storm, depending on estimated, or measured wind speeds.)   hope this answers your question.