The National Severe Storms Laboratory's storm spotters guide has more. Afternoon thunderstorms can merge into a large cluster of storms known as the mesoscale convective complex if favorable conditions are present. These complexes are responsible for a significant amount of summer season rain in the Plains. Favorable conditions form convective caps over the Plains which often precedes a severe thunderstorm outbreak. The following links show why thunderstorms produce hail and heavy rain and also why some are more dangerous than others.
Gust fronts can trigger new thunderstorms miles away.
Microbursts are strong winds that can blast down from thunderstorms. The Semi-official Microburst Handbook Homepage Tornadoes are strong winds in a vortex on the ground rising into a thunderstorm. The Tornado and Storm Research Organisation has information on severe thunderstorms and tornadoes in the United Kingdom and elsewhere in Europe. A useful tool for predicting thunderstorm severity is the lifted index . The National Weather Service issues watches and warnings for dangerous thunderstorms.