Address science standards and chronological order with one quick text.
When my kids were growing up, they constantly asked, "Why?" These questions were especially common in the summer, when we drove far and wide to explore Pennsylvania's state parks. I had to keep a step ahead of them to explain the phenomena they saw around them: mountains, rivers, waterfalls, and storms. So when I sat down to write a chronological order text about a scientific process, I reached back to our long car trips to write about the development of a thunderstorm.
Reading level: Fifth grade, lexile 750
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Thunderstorms
Imagine swimming on a hot, sunny day. Only a few puffy clouds dot the sky. As the afternoon goes on, those bright, billowing clouds turn dark and threatening. A distant streak of lightning causes a rumble of thunder. Before there is time for one last game of ‘Marco Polo’, the lifeguard blows the whistle and calls everyone out of the pool. Another swimming day ruined by a summer thunderstorm.
Hot Air Rises
It might seem as if thunderstorms exist only to ruin summer fun. But there is a scientific explanation for these swiftly forming storms. Have you ever seen a hot air balloon? If so, you have seen that hot air rises.
This is what happens on summer days. Warm, moist air rises into the atmosphere. In some situations, this air quickly cools, and no thunderstorm forms. But on certain days, the rising air is relatively warmer than the air surrounding it. It continues to rise. A thunderstorm begins to form.
As the warm air rises, it begins to cool. The moisture begins to condense, or turn from a gas to a liquid. This forms a cloud. The cloud grows as more warm air rises and moisture condenses. Columns of warm air are called updrafts. The water and ice droplets inside the cloud build up an electrical charge. Eventually, lightning can be seen.
Ice droplets from high in the cloud melt as they fall, turning into rain. When this falling rain causes downdrafts, the thunderstorm is fully formed, or mature. Lightning flashes and thunder booms. Often, thunderstorms don’t last long. A short storm quickly rains itself out and dissipates, or falls apart. The storm may vanish within half an hour. These short storms are called single-cell thunderstorms.
Multi-cells and Supercells: No swimming for you!
After a single-cell thunderstorm, the sun may come out. Everyone can get back into the pool. Summer fun is on the schedule!
But, as you have probably experienced, some storms last much longer than 30 minutes. Longer storms can happen in several ways. In some cases, thunderstorms form in clusters. These clusters can become a line of storms called a squall line. Each individual storm is fairly short-lived, but the line of them can last for hours. As long as thunder is rumbling, no one will be allowed back in the pool!
The most serious kind of thunderstorm is called a supercell. These storms occur when there is wind shear, changes in wind speed and direction, in the atmosphere. Supercells have strong updrafts and can be up to 15 miles wide. In many cases, supercells cause severe weather, including hail, flash floods, and tornadoes. When a supercell is nearby, swimming should be the last thing on your mind. Instead, work on finding a safe shelter from the storm.
Thunderstorms around the world
Whether they are single-cell, multi-cell, or supercell, thunderstorms are very common. As you read this sentence, there are probably about 2,000 storms going on around the world! In one year, there are more than 15 billion thunderstorms. But only ten percent of these are usually severe.
Thunderstorms do serve a purpose. They help to release energy from the atmosphere. In addition, thunderstorms balance out the electrical charges between the Earth and the atmosphere. No one really knows what would happen if there were no thunderstorms.
In the United States, the National Weather Service (NWS) monitors weather conditions. If conditions are right for a severe thunderstorm, meteorologists issue a severe thunderstorm watch. This tells people to be on alert. If a severe storm is headed your way, meteorologists issue a severe thunderstorm warning. This means that you should seek shelter.
The next time that you see darkening clouds on the horizon, don’t be upset. Even though you might lose out on some summer swimming time, you might get to see one of Earth’s most exciting events—a thunderstorm.
by Emily Kissner
©2024. Permission granted for single classroom use. This text may not be resold or included in any products offered for sale
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