Thunderstorm
Quick Facts
- A thunderstorm is a rain shower during which you hear thunder. Since thunder comes from lightning, all thunderstorms have lighting.
- Thunder is a sound made by a flash of lightning. When lightning heats the air around it, it causes the air to expand quickly. As it expands, a sound wave is created, making the sound of thunder.
• lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground.
How do lightning and thunder occur?
Lightning is an electrical discharge caused by imbalances between storm clouds and the ground or within the clouds themselves. Most lightning occurs within the clouds themselves.
Lightning happens when the negative charges (or electrons) at the bottom of the cloud are attached to the positive charges (or protons) on the ground.
The accumulation of the electric charges must be great enough to overcome the insulating properties of the air. When this happens, a stream of negative charges (electrons) pours down toward a high point where positive charges (protons) have clustered due to the pull of the thunderhead.
The connection is made and the positive charges are up to meet the negative charges. It is at this point that we see lightning and hear thunder. A bolt of lightning heats the air along its path, causing it to expand rapidly. Thunder is the sound caused by the rapidly expanding air.
Because electricity follows the shortest distance, most lightning bots are close to vertical. The short waves from nearer to the ground reach your ear first, followed by the crashing of the shock waves from higher up. Vertical lightning is often heard in one long rumble. However, if a lightning bolt is forked, the sounds change. The shock waves from the different forks of lightning bounce off each other, and the low-hanging clouds and nearby hills create a series of lower, continuous grumbles of thunder.
Where do thunderstorms form?
Thunderstorms are common occurrences on Earth. It is estimated that a lightning strike hits somewhere on Earth’s surface approximately 44 times every year, for a total of nearly 1.4 billion lightning strikes every year
A thunderstorm can develop and form at any geographical location, but most frequently in the mid-latitudes, where warm, moist air from tropical latitudes collides with cooler air from polar latitudes.
Compared to more active parts of the United States, thunderstorms are relatively rare in Alaska, North Dakota, New England, Montana, and other northern states where the air is generally cold.
Thunderstorms are usually rare along this particular coast since the summertime air there is relatively dry.
How far away is a thunderstorm?
A lightning discharge usually just strikes one spot on the ground, but it travels many miles in the air. When you listen to thunder, you’ll first hear the thunder created by that portion of the lightning channel that is nearest to you. As you continue to listen, you’ll hear the sound created from the portion of the channel farther and farther away. Typically, a sharp crack will indicate that the lightning channel passed nearby. If the thunder sounded more like a rumble, the lightning was at least several miles away. The loud boom that you sometimes hear is created by the main lightning channel as it reaches the ground.
A general rule to know how far off a bolt of lightning is when you hear thunder if you count the number of seconds between the flash of lightning and the sound of thunder, and then divide by 5, you’ll get the distance in miles to the lightning: 5 seconds = 1 mile, 15 seconds = 3 miles, 0 seconds = very close.
What causes thunder?
Thunder is produced by lightning. When lightning strikes, the narrow channel of air through which it travels reaches up to 30,000 °C almost instantly. The air that is now heated to such a high temperature had no time to expand, so it is now at very high pressure. The high-pressure air then expands outward into the compressing air surrounding it, causing a disturbance that propagates in all directions away from the stroke. The disturbance is a shock wave for the first few yards, after which it becomes an ordinary sound wave or thunder.
Is it possible to have thunder without lightning?
No, it is not possible to have thunder without lightning. Thunder starts as a shock wave from the explosively expanding lightning channel when a large current causes rapid heating.
However, lightning may be seen but there is no thunder heard. This is either because thunder is rarely heard more than 20km away or because the atmospheric conditions lead to sound bending upwards and away from the surface.
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