• The National Weather Service defines diffrent types of thunderstorms.Mark Lewis/Photodisc/Getty Images
  
  Dark clouds, thunder, lightning, high winds and pelting rains are the ingredients and visual indicators of thunderstorms. Cumulus clouds growing vertically and forming towers are the beginnings of thunderstorms. Storms develop from the movement of warm, moist air rising through the atmosphere, with air currents being key to the severity. The water in rising moist air forms clouds with water droplets that have electrical charges creating lightning and thunder.
  
  From the ground, storms look similar but there are actually different types of thunderstorms.
  
  

Severe Thunderstorm

• Thunderstorms with winds over 50 mph hour are considered severe. The National Weather Service defines a severe thunderstorm as one "that produces a tornado, winds of at least 58 mph, and/or hail at least 3/4- inch in diameter."
  
  

Single Cell

• Single-cell thunderstorms, also called pulse thunderstorms, develop from updrafts of warm air through the atmosphere. They usually begin with cold fronts pushed in from the sea, colliding with warm air and moisture. Single-cell storms are normally short, lasting about half an hour, and are predicted when the air movement appears on radar. They produce dark clouds, thunder and rain, and are not categorized as severe.
  
  

Multicell Clusters

• Multicell clusters are groups of single-cell thunderstorms moving together. The strongest cells are at the center of the cluster and weaker cells fall apart at the outsides of the group. Multicell-cluster thunderstorms are more severe than single-cell storms and last longer. They produce clouds, thunder and lightning, rain and sudden high winds.
  
  

Multicell Line

• Multicell-line thunderstorms are many single-cell storms moving together in a line with a strong gust of wind at the head of the line. Usually pushed ahead of a cold front, they are referred to as a cold front as well. Multicell-line thunderstorms are severe storms producing heavy rains, frequent lightning, strong winds and even tornadoes. Strong winds are the most common accompanying feature of multicell-line storms.
  
  

Supercells

• Supercell thunderstorms are very large storms characterized by varying, strong, fast winds and churning updrafts. They usually create severe weather, including strong tornadoes, flash floods, large hailstones and dangerous winds moving more than 80 mph. Most tornadoes are formed during supercell storms.
  
  There are three groups of supercells: rear flank with little rain; classic with a wall cloud; and front flank with a lot of rain. Wall clouds may be seen from very far off before other signs of impending storms are apparent.