Thunderstorms produce lightning because of the electrical charges produced in the clouds. The clouds become electrically charged due to static electricity that builds up when the water molecules are bounced around inside the cloud. The stronger the updraft winds, the more lightning. The negative electrical charge builds up at the base of the cloud and a positive charge builds up on the ground. Since positive and negative charges attract they meet to form a bolt of lightning. Sometimes when lightning is about to strike people may feel the hair stand up on their arms or the back of their neck because of the positive charges; that should be taken as a warning to seek shelter immediately. The tallest objects around are most likely to be struck, that is why people should never stand under a tree or be up on a mountain top during a thunderstorm. Lightning is 5 times hotter than the surface of the sun (54,000 degrees F), that sudden heat causes a rapid expansion of the air which results in the sound of thunder. The distance of lightning can be calculated by counting how many seconds it takes to hear the thunder after seeing a bolt of lightning, 5 seconds = 1 mile. Thunderstorms often preceed a rapid change in the weather if they are ushered in by an advancing cold front or warm front. Storms are associated with low pressure systems
, the stronger the storm, the lower the barometric pressure. Hurricane Katrina had the 3rd lowest pressure readings ever recorded at 27.11 inches of mercury. Low pressure is caused by rising warm air, it is a bit difficult to breathe during a hurricane because the air pressure is so low. Low pressure systems, which move counter-clockwise, bring rain and bad weather, they are indicated by a red "L" on a weather map. High pressure systems
on the other hand bring nice weather. The cooler, drier air sinks, it moves in a clockwise pattern. These systems are indicated by a blue "H" on a weather map. This is the Japanese Peace Bell in the park at the Civic Center in Oak Ridge.
For more information on thunderstorms, see: Thunderstorm info