Thunderstorms One of Natures Most Exotic Events

Unlike ordinary rain storms, thunderstorms have a delicate balance of airborne water vapor that is whipped by convection cells, and then chilled to the point of condensation. The newly created precipitation is combined with wind and lightning to create a distinct and flavorful storm that is known all over the world as a thunderstorm. Thunderstorms can vary according to recipe or ingredients. Some special thunderstorms have hail or powerful wind gusts added to them. A powerful and spicy thunderstorm will include a tornado.

Recipe for a Thunderstorm  Energy: This comes from the sun. As the sun warms the ground through radiation, the ground radiates that warmth into the air, heating the air. Ingredients  Water Vapor: As the sun warms the ground it causes water to evaporate and become water vapor.  Convection: Warm air rises, cool air sinking. All thanks to the sun.  Updraft: A pocket of rising warm air.  Downdraft: Sinking cool air.

Procedure FIRST: Add energy from the sun to warm the ground which in turn warms the air above it. SECOND: Add an updraft. This carries the water vapor aloft. Aloft, the water vapor cools into water droplets forming clouds. Eventually the clouds become so heavy with water droplets, it begins raining. THIRD: Add a downdraft. As the rain falls it cools the air around it which causes the downdraft. FOURTH: Add a convection cell. Actually it creates itself once the updraft and downdraft are added

The animation above shows how updrafts and downdrafts work against each other in a thunderstorm. This animation shows how updrafts and down drafts work against one another in a thunderstorm. But wait! Where’s the thunder? We’ll get to that later.

Stages of a Thunderstorm Each updraft and downdraft in a thunderstorm is considered a separate unit called a convection cell. These cells are continually developing and dying if the conditions are right. A thunderstorm cell can last between 30 to 60 minutes. As one cell is dying, another could be forming. This increases the life, and dangerous weather, of a thunderstorm. We can break down each convection cell into three distinct stages; the cumulus stage, the mature stage, and the dissipating stage.

C u m u l u s S t a g e  As updrafts carry water vapor aloft the water vapor condenses forming a cumulus cloud.  During this stage, cumulus clouds can grow both in height and width.  In a short time, the clouds can reach around 30,000 feet in height.  Cumulus clouds may also merge together during this vertical development, creating a single cloud that can cover an area of 5 to 10 miles.

M a t u r e S t a g e  Begins when the first drop of precipitation hits the ground. This occurs when the water droplets are too heavy for the updraft to hold aloft.  Cloud tops exceed 60,000 feet in height  Strong winds at these altitudes cause the tops of the clouds to level off, and take an anvil shape. The "anvil" is so high and temperatures are so low that the top of the cloud is composed entirely of ice crystals.

M a t u r e S t a g e (continued )  A thunderstorm is strongest toward the end of the mature stage. Rain will be the heaviest and lightning is abundant. This is when hail, strong winds and even tornadoes may form. We’re still waiting on the thunder…..

D I s s I p a t I n g S t a g e  This is the end of a thunderstorm.  Precipitation falls through the cloud, breaking it up.  Humidity in the air drops and the precipitation ends. Ah, still waiting on thunder….

CLOUD-TO-CLOUD LIGHTNING (then comes thunder, ok?)  In storm clouds tiny particles move about picking up a positive or negative electrical charge. Like when shoes scuff a rug.  Because of differences in mass, the positive charges collect at the top of the cloud and the negative charges collect at the bottom of the cloud.  Positive and negative charges attract each other. When the power of attraction between them gets too great, the particles discharge their energy at each other in a flash of electricity called lightening.

CLOUD-TO-GROUND LIghtnInG  The excess electrons at the bottom of a cloud create a channel of charged air called a “leader” that reaches down to the ground below  It's the negative charges in the bottom of the cloud that cause lightning to strike the ground.  The leaders attract other charged ground-based channels called “streamers”.  When the leader from the cloud meets a streamer from the ground, the path is ready. An electrical current called the return stroke, travels back up the path and you have lightning.

T H U N D E R  A bolt of lightning heats the air in a fraction of a second to between 15,000 to 60,000 F 0. That's hotter than the surface of the sun!  The heated air expands violently then contracts.  This rapid expansion creates a sound wave which we call thunder. Because light travels much faster than sound, you will always see lightning before you hear the thunder. It sound about five seconds to travel one mile. Try this applet and see. You can move the person closer or further from the storm cloud. Once you see the lightning, start counting “one-on-thousand”, “two-one-thousand”, etc.