Under Optimum Conditions
Under optimum conditions, the most intense thunderstorms can be seen at up to 100 miles (161 km) over flat terrain or water when the clouds are illuminated by large lightning discharges. However, an upper limit of 30-50 (48–80 km) miles is more common due to topography, trees on the horizon, low to mid level clouds, and the fact that local visibilities are generally no more than 25 miles (40 km). Variability of anvil height (an anvil is the large, plume-like top of a thunderhead) also contributes—45,000 feet (13,715 m) is very common in the mid latitudes for warm season thunderstorms, but the anvil height can range from 35,000 (10,665 m) to a current record of 78,000 feet (23,770 m). There is evidence that suggests some cases of heat lightning are, in fact, slow, diffuse discharges of electricity. This is not to be confused with electrically-induced luminosity actually generated at mesospheric altitudes above thunderstorm systems (and likewise visible at exceedingly great ranges), a phenomenon known as "sprites."
Read more about this topic: Heat Lightning
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