Description: There are three main types of convective storms: airmass thunderstorms, severe thunderstorms and hurricanes. These storms are all driven by the release of latent heat into the atmosphere during condensation of water vapor. Severe thunderstorms include both squall line thunderstorms and tornados. They acquire energy from water vapor in the atmosphere over land and therefore typically require warm air temperatures and high humidity. Hurricanes gain energy from water vapor evaporated from the ocean surface. This requires warm ocean temperatures, and is the reason hurricanes weaken over land. Hurricanes are cyclonic and therefore also require a non-zero Coriolis force to form and maintain their structure. For this reason they cannot form over the equator and cannot cross the equator.