With the exception of the intense summer heat, Arizona is a great place to live, or retire to. However, those who have lived here, and experienced the fury of Monsoon thunderstorms know that Arizona can hold its own with any state in the country when it comes to severe weather - especially during the summer thunderstorm season. The following cases represent some of the more impressive weather events that have occurred across Arizona, with special emphasis on the Phoenix Metropolitan area. Supercells are thunderstorms that are unique in that they contain strong rotation, or spin, within the core of the storm. A tornado is a violently rotating column of air, on a rather small scale, and this rotation is derived from the larger-scale rotation present within the supercell.
Wind shear is a change in the wind's direction, or speed, or both, with height.
For example, if the winds at the surface were from the southeast at 10 mph, and at 10000 feet aloft they were from the southwest at 50 mph, the atmosphere would possess strong wind shear. A supercell storm is considered a severe thunderstorm, in that it can produce tornadoes, as well as damaging winds and large hail. Severe, supercellular storms need more than just wind shear to develop, they need an atmosphere that is very unstable. However, on most occasions, the winds aloft are rather weak, and the wind shear in the atmosphere is not sufficient to promote the development of supercells. Thus, supercells and their associated tornadoes are very rare during the Arizona summer.