9781422269565

FACING THE WEATHER

BLIZZARDS EARTHQUAKES FLOODS HURRICANES TORNADOES

FACING THE WEATHER

JACQUELINE HAVELKA

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Copyright © 2024 by Mason Crest, an imprint of National Highlights, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, taping, or any information storage and retrieval system, without permission in writing from the publisher. Printed in the United States of America First printing 9 8 7 6 5 4 3 2 1 Series ISBN: 978-1-4222-4861-4 Hardcover ISBN: 978-1-4222-4866-9 ebook ISBN: 978-1-4222-6956-5 Cataloging-in-Publication Data on file with the Library of Congress Developed and Produced by National Highlights, Inc. Editor: Jacqueline Havelka—Inform Scientific Cover and Interior Design, and layout by Priceless Digital Media, LLC Publisher’s Note: Websites listed in this book were active at the time of publication. The publisher is not responsible for websites that have changed their address or discontinued operation since the date of publication. The publisher reviews and updates the websites each time the book is reprinted.

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Chapter 1: What Makes a Tornado..........................................................7 Chapter 2: Interesting Facts about Tornadoes......................................17 Chapter 3: Greatest Tornadoes of All Time...........................................27 Chapter 4: Monitoring a Tornado..........................................................43 Chapter 5: Staying Safe in a Tornado....................................................61 Series Glossary of Key Terms..............................................................72 Further Reading and Internet Resources..............................................74 Organizations to Contact......................................................................76 Index....................................................................................................77 Author’s Biography and Photo Credits..................................................80

KEY ICONS TO LOOK FOR:

Words to Understand: These words with their easy-to-understand definitions will increase the reader’s understanding of the text while building vocabulary skills.

Sidebars: This boxed material within the main text allows readers to build knowledge, gain insights, explore possibilities, and broaden their perspectives by weaving together additional information to provide realistic and holistic perspectives. Educational Videos: Readers can view videos by scanning our QR codes, providing them with additional educational content to supplement the text. Examples include news coverage, moments in history, speeches, iconic sports moments, and much more!

Text-Dependent Questions: These questions send the reader back to the text for more careful attention to the evidence presented there.

Research Projects: Readers are pointed toward areas of further inquiry connected to each chapter. Suggestions are provided for projects that encourage deeper research and analysis. Series Glossary of Key Terms: This back-of-the-book glossary contains terminology used throughout this series. Words found here increase the reader’s ability to read and comprehend higher-level books and articles in this field.

WORDS TO UNDERSTAND

altitude: the height of an object above the earth’s surface condensation: the process by which gas changes to a liquid mesocyclone: a well-defined radial circulation within a supercell thunderstorm meteorologists: a professional who forecasts, studies and reports weather conditions supercell: a large, persistent, and rotating thunderstorm

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CHAPTER

WHAT MAKES A TORNADO Have you ever been in a tornado? It was a scary experience, wasn’t it? What makes a tornado? For a tornado to form, certain atmospheric conditions must be present and come together to create these powerful storms. First, there must be instability in the atmosphere. This instability is usually caused by temperature and moisture differences at different altitudes . Wind shear is also needed; this means a change in wind speed and direction at various heights in the clouds. If warm, moist air is present, these combined conditions may lead to the formation of a tornado, a powerful and destructive rotating column of air. Supercell Tornadoes Tornadoes usually occur during severe thunderstorms, particularly supercell thunderstorms. Supercells are large, persistent, and rotating thunderstorms that have the potential to produce tornadoes. Meteorologists still do not completely

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understand the exact mechanisms behind the formation of tornadoes within supercells. Tornado formation is a highly complex process and scientists are still actively researching how they form. Here is what scientists do know. Within a supercell, an updraft occurs. An updraft is a column of rapidly rising air that is created by the collision of warm, moist air at the ground surface and cooler air at higher points. Wind shear is also needed to create a tornado. Winds at the ground level might be blowing south at 5 miles per hour (8 kph),

This is an incredibly beautiful picture of a supercell forming over Chaparral, New Mexico. Notice the trees and utility poles' size in comparison to the size of this massive cloud formation.

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Facing the Weather: Tornadoes

whereas winds higher up at 5,000 feet altitude might be blowing east at 25 mph (40 kph). This creates a shear that begins to create an invisible tube of air that begins to rotate horizontally. The updraft carries the warm air upward, which promotes the formation of a strong thunderstorm. Once the updraft is rotating and warm, moist air is flowing up into the tube, a tornado can form. The updraft becomes more intense, and as it strengthens, a rotating column of air called a mesocyclone forms when wind shear causes the updraft to horizontally rotate. The rising air within the storm tilts the rotating air from horizontal to vertical. At this point, the storm continues to develop and cool air descends downward from the core of the storm. This is called a downdraft, and it wraps around the mesocyclone, strengthening the rotating air. The downdraft helps give the tornado more structure. A specific type of downdraft called a rear flank downdraft (RFD) forms on the back side of the storm and also wraps around the mesocyclone. The updraft and mesocyclone become strong enough and the atmospheric conditions help form what is known as a wall cloud beneath the storm. A wall cloud is a very low, flat base of the storm that forms before a tornado develops. The tornado funnel will then develop within the wall cloud. The air within the funnel continues to rotate, and a drop in air pressure occurs. Moisture (water droplets) inside the funnel results in condensation and as a result, a visible funnel appears. The funnel extends downward from the base wall cloud. If you see dust and debris beneath the condensation funnel, that indicates the presence of a tornado. When the funnel comes into contact with the ground, a tornado is born.

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What Makes a Tornado

The long, flat, dark cloud is a wall cloud. Look at the size of it in relation to the house pictured below it!

The most destructive tornadoes originate from supercells, which can also produce severe winds, lightning, flash floods and damaging hail. Tornadoes generated from a supercell thunderstorm are definitely the most common and the most dangerous, but only about 20 percent of all supercell

thunderstorms produce a tornado. Non-Supercell Tornadoes

Some tornadoes form from a long line of strong thunderstorms called quasi-linear convective systems (QLCS). These tornadoes are weaker and shorter-lived than supercell tornadoes, and tend to occur late at night or early in the morning. The long line of strong thunderstorms is called a squall line. These thunderstorms usually form east of the Rocky Mountains in the United States, and usually form during springtime when atmospheric conditions are right. One common type of squall line is the bow echo which resembles an arched bow of storms.

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Facing the Weather: Tornadoes

This weather radar image shows severe weather that affected Illinois and Indiana. The line of storms, pictured in red, shows the traditional bow echo pattern. Landspouts are also a type of non-supercell tornado. These formations have a very narrow funnel that looks like a rope. A landspout typically forms over land while a thunderstorm cloud is still building, but before the rotating updraft forms. These storms therefore tend not to be very strong. Waterspouts are very similar to landspouts except that they form over water and also tend to be of weaker strength. More about Tornadoes Tornadoes occur on almost all continents, including Africa, Asia, Europe, and South America. They even occur in Australia and New Zealand, and frequent tornadoes occur in Bangladesh and Argentina. However, most tornadoes occur in the United States.

This amazing video will tell you everything you need to know about how a tornado forms.

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What Makes a Tornado

Official tornado records only date back to 1950, which indicate about 1,200 tornadoes hit the US every year. By comparison, New Zealand experiences only about 20 tornadoes per year. Tornadoes have been reported in all 50 states. Why does the US get the most tornadoes? Scientists say it largely has to do with geography. Tornadoes form when cold, dry air clashes with warm humid air. Many of the 48 continental states (which does not include Hawaii and Alaska) are situated

This weather radar image shows severe weather that affected Illinois and Indiana. The line of storms, pictured in red, shows the traditional bow echo pattern.

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Facing the Weather: Tornadoes

WEATHER WONDER

Most mesocyclones do not generate tornadoes. When a tornado does form, a small region of stretching occurs where the updraft meets the downdraft. The area is no larger than 0.62 miles (1 kilometer) in diameter and scientists still do not know the reasons that the stretching zone forms.

This is a great example of a waterspout. You can see the characteristic narrow rope-like funnel. These boats have a good, and scary, view!

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What Makes a Tornado

between the Rocky Mountains and the Gulf of Mexico. Dry air coming from the Rockies meets warm air coming from the Gulf, creating perfect conditions for a tornado in all those states in between. This part of the central US is called Tornado Alley , and it includes large portions of Texas, Oklahoma, Nebraska, and Kansas.

The central part of the US between the Rockies and the Gulf of Mexico is referred to as Tornado Alley.

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Facing the Weather: Tornadoes

TEXT-DEPENDENT QUESTIONS

1. What are the two main types of tornadoes and how do they differ? 2. What is a bow echo? 3. Why does the US get more tornadoes than any other part of the world?

RESEARCH PROJECT

Do your own research on supercell formation. Use the websites listed at the end of this book. Find information about supercells that is not in this book. What did you learn? Have a group of friends do this with you. Each of you can do your own research, then meet to find out what everyone learned.

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What Makes a Tornado

WORDS TO UNDERSTAND

convergency: merging or moving toward one another dissipate: to break up, thin, or scatter obscures: hidden or not clearly seen trajectory: a path, progression, or line of development vorticity: a state of local rotation

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