Meteorological drought is the measure of the dryness of an area in comparison to the normal average and the duration of the dry period.
This measure can only be applied to regions which have a year round precipitation regime such as tropical rain forests.
Meteorological drought happens when dry weather pattern dominates an area.
Meteorological drought can begin and end rapidly.
Meteorological drought is controlled by: ocean currents, jet streams and atmospheric cells.
Ocean Currents: ocean currents affect drought because they control the waters temperatures of another region. If the waters around the Sahara desert were warm then the water would evaporate and cause precipitation whereas when the waters are cold no air will rise which means no rain and high pressure.
Jet Streams: jet streams can throw the weather system of high pressure which the deserts have away or push a low pressure system over the top of a desert and cause precipitation.
Atmospheric Cells: The Hadley and Ferrel cells where they converge is where the deserts are located. The area in which these cells converge is where the high pressure for the deserts is found.