Water droplets and ice fly up through the cloud in updrafts. When these droplets get heavy enough, they fall. This starts a downdraft, and soon there is a convection cell within the cloud. The cloud grows into a cumulonimbus giant. Eventually, the drops become large enough to fall to the ground.
At this time, the thunderstorm is mature, and it produces gusty winds, lightning, heavy precipitation, and hail Figure below. The downdrafts cool the air at the base of the cloud, so the air is no longer warm enough to rise. As a result, convection shuts down. Without convection, water vapor does not condense, no latent heat is released, and the thunderhead runs out of energy.
A thunderstorm usually ends only 15 to 30 minutes after it begins, but other thunderstorms may start in the same area. With severe thunderstorms, the downdrafts are so intense that when they hit the ground it sends warm air from the ground upward into the storm.
The warm air gives the convection cells more energy. Rain and hail grow huge before gravity pulls them to Earth. Severe thunderstorms can last for hours and can cause a lot of damage because of high winds, flooding, intense hail, and tornadoes. Thunderstorms can form individually or in squall lines along a cold front. In the United States, squall lines form in spring and early summer in the Midwest where the maritime tropical mT air mass from the Gulf of Mexico meets the continental polar cP air mass from Canada Figure below.
Cold air from the Rockies collided with warm, moist air from the Gulf of Mexico to form this squall line. So much energy collects in cumulonimbus clouds that a huge release of electricity, called lightning , may result Figure below. The electrical discharge may be between one part of the cloud and another, two clouds, or a cloud and the ground.
Lightning heats the air so that it expands explosively. The loud clap is thunder. Light waves travel so rapidly that lightning is seen instantly. Sound waves travel much more slowly, so a thunderclap may come many seconds after the lightning is spotted. Thunderstorms kill approximately people in the United States and injure about Americans per year, mostly from lightning strikes.
Tornadoes , also called twisters, are fierce products of severe thunderstorms Figure below. As air in a thunderstorm rises, the surrounding air races in to fill the gap, forming a funnel. A tornado is a funnel shaped, whirling column of air extending downward from a cumulonimbus cloud.
The formation of this tornado outside Dimmit, Texas, in was well studied. A tornado lasts from a few seconds to several hours.
The average wind speed is about kph mph , but some winds are much faster. A tornado travels over the ground at about 45 km per hour 28 miles per hour and goes about 25 km 16 miles before losing energy and disappearing Figure below. An individual tornado strikes a small area, but it can destroy everything in its path. Most injuries and deaths from tornadoes are caused by flying debris Figure below. In the United States an average of 90 people are killed by tornadoes each year. Tornadoes form at the front of severe thunderstorms.
Lines of these thunderstorms form in the spring where where maritime tropical mT and continental polar cP air masses meet. Although there is an average of tornadoes annually, the number of tornadoes each year varies greatly Figure below. Explanation: When two different fronts collide, rainstorms and snowstorms form.
James J. It is entirely dependent on what type of storm you are talking about. Explanation: As far as storms go, there are many processes involved. Related questions Where are the strongest winds in a tropical storm? How is the strength of tropical storms measured? What is the eye wall and what causes it formation?
How does the latent heat created due to precipitation formation aid in storm formation? What atmospheric conditions are necessary to produce tropical storms? Winds in the storm cloud column spin faster and faster, whipping around in a circular motion.
When the winds reach between 25 and 38 mph, the storm is called a tropical depression. When the wind speeds reach 39 mph, the tropical depression becomes a tropical storm.
This is also when the storm gets a name. The winds blow faster and begin twisting and turning around the eye, or calm center, of the storm. Wind direction is counterclockwise west to east in the northern hemisphere and clockwise east to west in the southern hemisphere.
This phenomenon is known as the Coriolis effect. When the wind speeds reach 74 mph, the storm is officially a hurricane. The storm is at least 50, feet high and around miles across. The negatively charged cloud base also repels electrons on the ground, creating a positive charge there. The rapid heating and expansion of the surrounding air causes the characteristic rumble of thunder that accompanies the flash of light.
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