The building block of all thunderstorms is the thunderstorm cell. The thunderstorm cell has a distinct life-cycle that lasts about 30 minutes.
A cumulus cloud begins to grow vertically, perhaps to a height of 20, feet 6 km. Air within the cloud is dominated by updraft with some turbulent eddies around the edges.
The storm has considerable depth, often reaching 40, to 60, feet 12 to 18 km. Every thunderstorm produces lightning, which kills more people each year than tornadoes. Strong winds, hail, and tornadoes are also dangers associated with some thunderstorms. You can estimate how many miles away a storm is by counting the number of seconds between the flash of lightning and the clap of thunder.
Divide the number of seconds by five to get the distance in miles. The lightning is seen before the thunder is heard because light travels faster than sound. Thunderstorms are most likely to occur in the spring and summer months and during the afternoon and evening hours, but they can occur year-round and at all hours of the day or night. Straight-line wind is a term used to define any thunderstorm wind that is not associated with rotation, and is used mainly to differentiate from tornadic winds.
What is a downdraft? A downdraft is a small-scale column of air that rapidly sinks toward the ground. What is a downburst? A downburst is a result of a strong downdraft. A downburst is a strong downdraft with horizontal dimensions larger than 2. Imagine the way water comes out of a faucet and hits the bottom of the sink. Downburst winds may begin as a microburst and spread out over a wider area, sometimes producing damage similar to a strong tornado.
Although usually associated with thunderstorms, downbursts can occur with showers too weak to produce thunder. What is a microburst? A microburst is a small concentrated downburst that produces an outward burst of damaging winds at the surface. Microbursts are generally small less than 4km across and short-lived, lasting only minutes, with maximum windspeeds up to mph. What is the difference between a microburst and a downburst? A microburst is less than 4 km across, and a downburst is greater than 4 km across.
What are the different types of microbursts? There are two kinds of microbursts: wet and dry. A wet microburst is accompanied by heavy precipitation at the surface.
Dry microbursts, common in places like the high plains and the intermountain west, occur with little or no precipitation reaching the ground. What is a gust front? A gust front is the leading edge of rain-cooled air that clashes with warmer thunderstorm inflow. Gust fronts are characterized by a wind shift, temperature drop, and gusty winds out ahead of a thunderstorm.
Sometimes the winds push up air above them, forming a shelf cloud or detached roll cloud. What is a gustnado? A gustnado is a short-lived, ground-based swirling wind that can form on the leading edge of a severe thunderstorm.
A gustnado develops in a different way than a classic tornado does. What is a derecho? A derecho is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. A typical derecho consists of numerous microbursts, downbursts, and downburst clusters. What is a haboob? A haboob is a wall of dust that is pushed out along the ground from a thunderstorm downdraft at high speeds.
Are damaging winds really a big deal? Damage from severe thunderstorm winds account for half of all severe reports in the lower 48 states and is more common than damage from tornadoes. Wind speeds can reach up to mph and can produce a damage path extending for hundreds of miles. Who is at risk from damaging winds? Since most thunderstorms produce some straight-line winds as a result of outflow generated by the thunderstorm downdraft, anyone living in thunderstorm-prone areas of the world is at risk for experiencing this hazard.
People living in mobile homes are especially at risk for injury and death. Even anchored mobile homes can be seriously damaged when winds gust over 80 mph. How are damaging winds detected? Doppler radar is a critical tool for damaging wind detection because these hazards have certain patterns in the data collected near the surface and in middle levels of the storm.
Doppler radar velocity data can show areas of diverging winds at the surface, and even the strength of those winds, indicating a downburst or microburst.
Winds coming together at upper levels of the storm convergence can also be seen on velocity displays, and can indicate the development of a downburst or microburst. A bow echo is a radar echo that is linear but bent outward in a bow shape. Areas of circulation also can develop at either end of a bow echo, which sometimes can lead to tornado formation — especially in the left usually northern end, where the circulation shows cyclonic rotation.
If the air is sufficiently moist, then the moisture condenses to become a cumulus cloud. Thunderstorm Facts The typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Thunderstorms happen in every state and every thunderstorm has lightning. Thunderstorms may occur singly, in clusters, or in lines. Some of the most severe occur when a single thunderstorm affects one location for an extended time. Thunderstorms typically produce heavy rain for a brief period, anywhere from 30 minutes to an hour.
Warm, humid conditions are highly favorable for thunderstorm development. About 10 percent of thunderstorms are classified as severe—one that produces hail at least three-quarters of an inch in diameter, has winds of 58 miles per hour or higher, or produces a tornado. Click Here to see if there are any active warnings in your area. Look for darkening skies, flashes of lightning, or increasing winds.
If you hear the sound of thunder, go to a safe place immediately. The best place to go is a sturdy building or a car, but make sure the windows in the car are shut. Avoid sheds, picnic areas, baseball dugouts and bleachers.
If there is no shelter around you, stay away from trees. Crouch down in the open area, keeping twice as far away from a tree as far as it is tall. Put your feet together and place your hands over your ears to minimize hearing damage from thunder. Swimming, wading, snorkeling and scuba diving are not safe. Stay away from clotheslines, fences, and drop your backpacks because they often have metal on them. Do not use a corded telephone. Lightning may strike exterior phone lines.
As the air rises, it transfers heat from the surface of the earth to the upper levels of the atmosphere the process of convection. The water vapor it contains begins to cool, releases the heat, condenses and forms a cloud. The cloud eventually grows upward into areas where the temperature is below freezing. As a storm rises into freezing air, different types of ice particles can be created from freezing liquid drops.
The ice particles can grow by condensing vapor like frost and by collecting smaller liquid drops that haven't frozen yet a state called "supercooled". When two ice particles collide, they usually bounce off each other, but one particle can rip off a little bit of ice from the other one and grab some electric charge. Lots of these collisions build up big regions of electric charges to cause a bolt of lightning, which creates the sound waves we hear as thunder.
The Thunderstorm Life Cycle Thunderstorms have three stages in their life cycle: The developing stage, the mature stage, and the dissipating stage. The developing stage of a thunderstorm is marked by a cumulus cloud that is being pushed upward by a rising column of air updraft. The cumulus cloud soon looks like a tower called towering cumulus as the updraft continues to develop. There is little to no rain during this stage but occasional lightning.
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