Weather - Meteorology

WEATHER

There are many different forms of weather on planet Earth. Some that accur day-to-day and others tah accur on a more rare basis. Weather is a very broad topic but can be broken down. In my composition, I will explain three types of weather: Lightning, Ice Storms, and Hurricanes. The reson I chose these three topics is to inform people about the different types of weather. Some of it we may already know. But there are others that we know nothing about.

Lightning has been feared as an atmospheric flash of supernatural origin. The Greeks marveled and feared lightning as it was hurled by Zeus. For the Vikings, lightning was produced by Thor as his hammer struck an anvil while riding his chariot across the clouds. In the East, early statues of Buddha show him carrying a thunderbolt with arrows at each end. Indian tribes in North America believed that lightning was due to the flashing feathers of a mystical bird whose flapping wings produced the sound of thunder. Today we use a more scientific approach to explain lightning. Lightning is a visible electrical discharge that results from the buildup of positive and negative charges within a thunderstorm. When the buildup is strong enough, lightning appears. This discharge produces a series of brilliant flashes inside clouds, between the clouds, and between the clouds and the ground. The average time interval between each stroke is approximately 0.02 seconds. Each stroke lasts, on average, 0.25 seconds. It is estimated that there are 2,000 thunderstorms occurring on earth at all times. This results in 100 lightning strikes occurring around the world every second, totaling 8.6 million strikes per day and over three billion each year. Lightning originates in a thunderstorm cloud where charged particles are separated. There are several theories explaining how they separate, but no one really knows what pulls the charges apart. It is believed that water drops in the cloud become negatively charged and, being heavier, fall to the bottom of the cloud. The positive charges are then swept up to the top of the cloud by the warm updrafts in the thunderhead. As more charges separate, parts of the cloud become so highly charged that the electrical forces tear nearby air molecules apart, making more charged fragments.

There are also many types of lightning. Cloud-to-ground lightning is the most damaging and dangerous form of lightning. Although it is not the most common type, representing only 20% of all lightning strikes, it is the one which is most understood. Most flashes originate near the lower negative charge center and deliver negative charge to the Earth. Some suggest that cloud-to-ground lightning strikes occur most at higher latitudes. Others suggest that cloud top height is a more important variable than latitude. Forked lightning is composed of crooked or branched channels. These bolts may discharge from a cloud to the ground, to another cloud, or out of the top or sides of a storm. Intra-cloud lightning is the most common form of lightning, accounting for 60% of all lightning. This occurs when opposite electrical charges in one cloud attract those in another. The formation of intra-cloud lightning takes place inside clouds and looks like a bright flash which flickers, to the observer. A flash may leave the cloud. When this occurs, it resembles the cloud-to-ground lightning bolt. Storms with the greatest vertical development most often produce intra-cloud lightning. Sheet lightning occurs when the lightning is obscured by clouds. The flashes illuminate the entire cloud, making it visible from miles away. With sheet lightning, the observer is near enough to hear the thunder. Heat lightning is very similar to sheet lightning, except the lightning is too far away for the observer to hear the thunder. The flashes are created by lightning bolts occurring in thunderstorms more than ten miles away. It is called heat lightning because it most often occurs during the summer, at night. St. Elmo's Fire is described as a greenish or bluish glow above pointed objects on the ground. This form of lightning is created by the soft glow of an electric field generated by a continuous flow of sparks. These tiny sparks are positive charges reaching skyward in response to a growing area of negative charge in clouds or air above. It was once thought to protect ships from lightning damage. However, if a thunderstorm is nearby, St. Elmo's Fire might precede a lightning strike. And finally, ball lightning is an extremely rare phenomenon. It is so rare, scientists often question its existence. Ball lightning is described as luminous balls coming from violent thunderstorms containing a lot of lightning. They are approximately four to eight inches in diameter and last less than five seconds. Ball lightning is sometimes accompanied by a crackling sound and a sulfurous smell. These incidents are reported to be attracted to metallic objects such as wire fences or telephone poles. Ball lightning does not usually cause damage, but it has been reported to burn through screens and windows.

Ice storms are a very intracate type of weather. It needs certain things to happen and the ice/snow has many forms. An ice storm is usually used to describe occasions when damaging accumulations of ice are expected during freezing rain situations. These accumulations of ice make walking and driving very dangerous. A great amount of ice accumulation are accumulations of 1/4 inch or greater. A situation that occurs once in a while is freezing rain. This occurs when rain or drizzle falls on surfaces (such as the ground, trees, power lines, motor vehicles, streets, highways, etc.) that have a temperature of 32o F or below making the water droplets to freeze on contact. Freezing rain is precipitation, but certain conditions have to be met to make moisture from the sky, and have the moisture fall in the form of freezing rain. First, particles of moisture are present in all clouds, but that doesn't result in any form of precipitation until the particles become too large (and heavy), and rain or another type of precipitation is the result.

Freezing rain is a specific type of precipitation, as is rain, drizzle, sleet, and hail. Before the rain hits the ground, it