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thunderstorm
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What is a thunderstorm?
A thunderstorm is a short-lived weather disturbance associated with lightning, thunder, heavy rain or hail, and strong winds. They arise when warm, moist air rises swiftly to cooler parts of the atmosphere, forming cumulonimbus clouds and precipitation. Cooled air columns descend, causing strong downdrafts and winds. Electrical charges accumulate on cloud particles, leading to lightning discharges that heat the air and create thunder.
Thunderstorms are most common in temperate and tropical regions, rare in polar areas, and infrequent above 50° N and 50° S latitudes. The United States sees maximum activity in Florida, the Gulf Coast, and the mountains of New Mexico. Central Europe and Asia average 20 to 60 thunderstorm days yearly. At any moment, there are roughly 1,800 thunderstorms worldwide.
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What are the main features of a thunderstorm?
A thunderstorm is a short-lived weather disturbance associated with lightning, thunder, dense clouds, heavy rain or hail, and strong, gusty winds.
Thunderstorms develop when the atmosphere is unstable to vertical motion, which can occur when warm, light air is overlain by cooler, heavier air. This causes the cooler air to sink and displace the warmer air upward, creating a strong, rising air current called an updraft. If the updraft is moist, water will condense and form clouds, releasing heat that further fuels the upward air motion.
The huge clouds associated with thunderstorms typically start as isolated cumulus clouds that grow vertically into domes and towers. These clouds can merge with other cells to form a cumulonimbus cloud, with its characteristic anvil-shaped top, billowing sides, and dark base, which produces large amounts of precipitation.
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How do thunderstorms form?
Thunderstorms arise from atmospheric instability, where warm, light air underlies cooler, heavier air. This causes the cooler air to sink and displace the warmer air upwards, creating a strong, rising air current called an updraft. If the updraft is moist, water condenses, forming clouds and releasing heat, which further fuels the upward motion. Surface heating by sunlight is a common trigger, as land heats faster than oceans. Mountains can also force winds upward. These huge clouds start as cumulus clouds, growing into cumulonimbus clouds with their characteristic anvil shape, ultimately producing precipitation, lightning, and thunder.
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What causes thunder and lightning during a thunderstorm?
During a thunderstorm, lightning is a visible electrical discharge caused by an imbalance of charges between a cloud region and another surface. This imbalance overcomes air resistance, creating a discharge.
Thunder is the sound produced by the rapid expansion of air heated by a lightning discharge. Lightning heats the air to extreme temperatures, causing it to expand rapidly and create a shock wave. This shock wave slows to the speed of sound as it travels through the atmosphere, producing the sound we hear as thunder.
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How can thunderstorms affect people and the environment?
Thunderstorms can be violent, short-lived weather disturbances associated with lightning, thunder, heavy rain or hail, and strong gusty winds. These storms can affect people and the environment in several ways:
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Flash floods Heavy rains from thunderstorms can cause flash floods, which are abrupt torrents of water that rush down low-lying areas and can destroy riverbeds, structures, roads, and bridges.
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Lightning damage Lightning strikes can damage the central nervous system, heart, lungs, and other vital organs if a person is struck. Lightning can also cause fires if a surge enters an unprotected residence.
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Hail damage Hail is extremely destructive to buildings and crops and may be dangerous to exposed animals.
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What are some ways people can stay safe during a thunderstorm?
During a thunderstorm, it's crucial to stay safe from lightning strikes. The best course of action is to stay inside a sturdy building or a car, avoiding contact with metal. Keep away from doors, windows, electrical appliances, and plumbing.
If you're caught outdoors, avoid isolated trees or tall objects. Crouch low to the ground to minimize your height and ground contact, but don't lie down. Swimming pools are unsafe due to water's conductivity. If you're in a mobile home, seek shelter in a sturdy building or a ditch, as mobile homes offer little protection from tornadoes due to their light construction and potential for disintegration.
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News •
thunderstorm, a violent short-lived weather disturbance that is almost always associated with lightning, thunder, dense clouds, heavy rain or hail, and strong gusty winds. Thunderstorms arise when layers of warm, moist air rise in a large, swift updraft to cooler regions of the atmosphere. There the moisture contained in the updraft condenses to form towering cumulonimbus clouds and, eventually, precipitation. Columns of cooled air then sink earthward, striking the ground with strong downdrafts and horizontal winds. At the same time, electrical charges accumulate on cloud particles (water droplets and ice). Lightning discharges occur when the accumulated electric charge becomes sufficiently large. Lightning heats the air it passes through so intensely and quickly that shock waves are produced; these shock waves are heard as claps and rolls of thunder. On occasion, severe thunderstorms are accompanied by swirling vortices of air that become concentrated and powerful enough to form tornadoes.
Thunderstorms are known to occur in almost every region of the world, though they are rare in polar regions and infrequent at latitudes higher than 50° N and 50° S. The temperate and tropical regions of the world, therefore, are the most prone to thunderstorms. In the United States the areas of maximum thunderstorm activity are the Florida peninsula (more than 80 thunderstorm days per year, with some areas over 100), the Gulf Coast (60–90 days per year), and the mountains of New Mexico (50–80 days per year). Central Europe and Asia average 20 to 60 thunderstorm days per year. It has been estimated that at any one moment there are approximately 1,800 thunderstorms in progress throughout the world.
This article covers two major aspects of thunderstorms: their meteorology (i.e., their formation, structure, and distribution) and their electrification (i.e., the generation of lightning and thunder). For separate coverage of related phenomena not covered in this article, see tornado, ball lightning, bead lightning, and red sprites and blue jets.
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Thunderstorm formation and structure
Vertical atmospheric motion
Most brief but violent disturbances in Earth’s wind systems involve large areas of ascending and descending air. Thunderstorms are no exception to this pattern. In technical terms, a thunderstorm is said to develop when the atmosphere becomes “unstable to vertical motion.” Such an instability can arise whenever relatively warm, light air is overlain by cooler, heavier air. Under such conditions the cooler air tends to sink, displacing the warmer air upward. If a sufficiently large volume of air rises, an updraft (a strong current of rising air) will be produced. If the updraft is moist, the water will condense and form clouds; condensation in turn will release latent heat energy, further fueling upward air motion and increasing the instability.
Once upward air motions are initiated in an unstable atmosphere, rising parcels of warm air accelerate as they rise through their cooler surroundings because they have a lower density and are more buoyant. This motion can set up a pattern of convection wherein heat and moisture are transported upward and cooler and drier air is transported downward. Areas of the atmosphere where vertical motion is relatively strong are called cells, and when they carry air to the upper troposphere (the lowest layer of the atmosphere), they are called deep cells. Thunderstorms develop when deep cells of moist convection become organized and merge, and then produce precipitation and ultimately lightning and thunder.
Upward motions can be initiated in a variety of ways in the atmosphere. A common mechanism is by the heating of a land surface and the adjacent layers of air by sunlight. If surface heating is sufficient, the temperatures of the lowest layers of air will rise faster than those of layers aloft, and the air will become unstable. The ability of the ground to heat up quickly is why most thunderstorms form over land rather than oceans . Instability can also occur when layers of cool air are warmed from below after they move over a warm ocean surface or over layers of warm air. Mountains, too, can trigger upward atmospheric motion by acting as topographic barriers that force winds to rise. Mountains also act as high-level sources of heat and instability when their surfaces are heated by the Sun.
The huge clouds associated with thunderstorms typically start as isolated cumulus clouds (clouds formed by convection, as described above) that develop vertically into domes and towers. If there is enough instability and moisture and the background winds are favourable, the heat released by condensation will further enhance the buoyancy of the rising air mass. The cumulus clouds will grow and merge with other cells to form a cumulus congestus cloud extending even higher into the atmosphere (6,000 metres [20,000 feet] or more above the surface). Ultimately, a cumulonimbus cloud will form, with its characteristic anvil-shaped top, billowing sides, and dark base. Cumulonimbus clouds typically produce large amounts of precipitation.
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