June 23-29, 2013 is National Lightning Safety Week.
Throughout this week the National Weather Service in Jackson will emphasize lightning safety.
Today we focus on the science of lightning.
Eyjafjallajökull Volcano, Iceland
For as long as humans have watched the skies it has fascinated and frightened them. Meteorologists know the cloud conditions necessary to produce lightning but cannot forecast the location or time of the next strike of lightning from a storm. At any given moment there are as many as 1800 thunderstorms in progress somewhere on the earth and each is capable of producing deadly lightning.
As a thunderstorm forms it produces ice in the upper portion of the cloud. The formation of ice in a cloud is an important element in the development of lightning. Those storms that fail to produce large numbers of ice crystals may also fail to produce lightning. Strong rising and sinking motions within the cloud are also important as they enhance collisions among cloud particles causing a separation of electrical charges. Positively charged ice crystals rise to the top of the thunderstorm and negatively charged ice particles and hailstones drop to the middle and lower parts of the storm. As the differences in charges continue to increase, positive charges rise up taller objects such as trees, houses, and telephone poles.
Have you ever been under a storm and had your hair stand up? Yes, the charge can also move up you! This is nature's final warning that you are in the wrong place, and you may be a lightning target! If this happens, you need to act quickly by getting to the nearest shelter!
The negatively charged area in the storm sends out a charge toward the ground called a step leader. It is invisible to the human eye and moves in steps in less than a second toward the ground. When it gets close to the ground, it is attracted by all of the positively charged objects and a channel develops. You see the electrical transfer in this channel as lightning. There may be several repeated transfers of electricity within the channel. You may observe the repeated transfers as flickering lightning.
Tomorrow we will discuss lightning safety outdoors.
For additional information... please contact the National Weather Service office in Jackson Mississippi or visit the lightning safety awareness week web site at http://www.lightningsafety.noaa.gov/.