Stormy weather is associated with heavy rain, hurricanes, tornadoes, typhoons, hail, sleet, tropical cyclones and general thunderstorms. Atmospheric instability is one of the causes of stormy weather, as well as high pressure zones moving in from certain directions. For example, a high pressure zone from the north causes colder weather as winter approaches and a high pressure zone from the south brings warm weather.
When a high pressure zone brings colder weather over an ocean and there exists a pressure differential between the atmosphere and water, hurricanes, tropical cyclones or typhoons can form. If wind shear is enough to alleviate the pressure, then the winds dissipate and do not reach the minimum 74 mph necessary to form a violent storm. The difference between a hurricane, a typhoon and a tropical cyclone is the location of the event. According to the Hurricane Research Division of the National Oceanic and Atmospheric Administration, hurricanes form in the Atlantic Ocean and Eastern Pacific, typhoons form in the northwest Pacific Ocean and tropical cyclones form in the Indian Ocean.
Less severe forms of stormy weather happen when warm air rises and cold air sinks. This dual action transfers heat from the land to the atmosphere and provides the energy necessary to drive a thunderstorm. Moisture must be present, because cloud condensation is an exothermic process that releases more energy to power the motion of the unstable air.