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Storms. Storms. A storm is a violent disturbance in the atmosphere 4 major types of storms: Thunderstorms Tornadoes Hurricanes Winter Storms A meteorologist is a scientist who studies weather and tries to predict it. Thunderstorms.
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Storms • A storm is a violent disturbance in the atmosphere • 4 major types of storms: • Thunderstorms • Tornadoes • Hurricanes • Winter Storms • A meteorologist is ascientist who studies weather and tries to predict it
Thunderstorms • A thunderstorm is a small storm often accompanied by heavy precipitation and frequent thunder and lightning. • Form in large cumulonimbus clouds (also called thunderheads) on hot, humid afternoons
Thunderstorms • Warm, humid air rises rapidly and the air cools, forming dense thunderhead clouds • Heavy rain falls, sometimes along with hail • Within the thunderhead cloud there are strong updrafts and downdrafts
Lightning • Lightning is a sudden spark, or electrical discharge • Positive and negative charges jump between parts of a cloud, or between nearby clouds, or between a cloud and the ground
Thunderstorms • Lightning heats the air to 30,000oC • Thunder is the sound of the rapidly heated air expanding suddenly and explosively • Light travels faster than sound so you see lightning before you hear thunder
Calculating Lightning Distances • Watch the sky for a flash of lightning. • Count the number of seconds until you hear thunder. • Divide the number of seconds by 5 to calculate the distance the storm is away from your location in miles (or divide by 3 for kilometers). • Ex: If you counted 18 seconds from when you saw the lightning, the strike was 3.6 miles (6 kilometers) from your location. Divide Number of Seconds by 3 for Distance in Kmor 5 for Distance in Miles.
Examples of types of Lightning • Spider-Flashes of spider lightning crawl across the sky for up to 90 miles. • Sheet lightning - Normal lightning that is reflected in the clouds • Heat lightning - Normal lightning near the horizon that is reflected by high clouds • Ball lightning - A phenomenon where lightning forms a slow, moving ball that can burn objects in its path before exploding or burning out • Red sprite - A red burst reported to occur above storm clouds and reaching a few miles in length (toward the stratosphere) • Blue jet - A blue, cone-shaped burst that occurs above the center of a storm cloud and moves upward (toward the stratosphere) at a high rate of speed • Ribbon lightning-Ribbonlightning occurs in thunderstorms with high cross winds and multiple return strokes. The wind will blow each successive return stroke slightly to one side of the previous return stroke, causing a ribbon effect. • Bead lightning- Bead lightning is a type of cloud-to-ground lightning which appears to break up into a string of short, bright sections, which last longer than the usual discharge channel. It is fairly rare. • Forked lightning-Forkedlightning occurs when a second lightning stroke doesn't follow the same path as the first lightning stroke. Thus, it appears forked.
Lightning Strikes in the U.S. • This map shows how often lightning strikes different parts of the lower 48 states. Central Florida has the most intense concentration of cloud-to-ground lightning because it has a lot of warm, humid air. The Pacific Northwest has almost no lightning.
Thunderstorm Safety • Go INSIDE! • Do NOT touch anything that can conduct electricity-especially metal objects and bodies of water • Crouch down in a low area-avoid trees
Tornadoes • A tornado is a rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch Earth’s surface
Tornado Formation • Warm, moist air flows in at the bottom of a cumulonimbus cloud and moves upward • A low pressure area forms inside the cloud • Warm air rotates as it meets winds blowing in different directions at different altitudes
Tornado Alley is an area of the United States that has a high frequency of tornadoes because cold, dry air moves south from Canada to meet warm, humid air from the Gulf of Mexico • 5 states that cross Tornado Alley are: • Texas • Oklahoma • Kansas • Nebraska • Iowa
The Fujita Tornado Damage Scale • Tornadoes are ranked on the Fujita scale by the amount of damage they cause
Tornado Safety • A tornado watch is an announcement that tornadoes are possible in your area. Stay tuned to the radio or television news. • A tornado warning is an announcement that a tornado has been sighted. Take shelter immediately! • The safest place to be during a tornado is in a storm shelter or the basement of a well-built building
Hurricanes • A hurricane is a tropical cyclone that has winds of 119 km/h or higher • Hurricanes form in the Atlantic, Pacific, and Indian Oceans • In the western Pacific Ocean, hurricanes are called typhoons • A hurricane begins over warm ocean water as a low-pressure area, or tropical disturbance. • A hurricane draws its energy from the warm, humid air at the ocean’s surface • As the air rises and forms clouds, more air is drawn into the system • Inside the storm are bands of very high winds and heavy rains • Winds spiral inward toward the area of lowest pressure at the center
Hurricane Names • Hurricanes are given names to help us identify them and track them as they move across the ocean • Men and women's names are used • One name for each letter of the alphabet except Q, U, and Z • World Meteorological Organization uses six lists in rotation • The only time a new name is added is if a hurricane is very deadly or costly • If that happens then the name is retired and a new name is chosen.
Hurricanes • Hurricanes last longer than other storms, usually a week or more • After a hurricane passes over land, it no longer has warm, moist air to draw energy from so it loses strength • A storm surge is a “dome” of water that sweeps across the coast where a hurricane lands • For safety during a hurricane, people are told to evacuate • Evacuate means to leave the area immediately
Winter Storms • All year round, most precipitation begins in clouds as snow • A large amount of humid air that cools below 0oC can produce a winter storm • Lake Effect Snow-areas east of the Great Lakes get a LOT of snow WHY?
Lake-Effect Snow • The land cools much more rapidly than the water in the Great Lakes (or any lake) • When a cold, dry air mass from central Canada moves southeast across one of the Great Lakes, it picks up water vapor and heat from the lake • As soon as the air mass reaches the other side of the lake, the air rises and cools again • The water vapor condenses and falls as snow • Cities such as Buffalo and Rochester, New York are two of the snowiest cities in the U.S. because they are located east of the Great Lakes