A tornado is a violently turning tube of air suspended from a thick cloud.It extends from a thunderstorm in the sky down to the ground.The shape is like a funnel：wide at the top，narrower at the bottom.

　　Tornadoes form when winds blowing in different directions meet in the cloud and begin to turn in circles.Warm air rising from below causes the wind tube to reach toward the ground.Because of their circular movement，these severe windstorms are also known as twisters.

　　Tornadoes have been observed on every continent except Antarctica.But weather experts say they are most common in the United States.Each year，the United States has more than one thousand tornadoes.

　　These storms can happen at any time of the year.But most happen from late winter to the middle of summer.There is a second high season in November.

　　During spring，warm air moves north and mixes with cold air remaining from winter.In November，the opposite happens.Cold weather moves south and combines with the last of the warm air from summer.

　　Tornadoes can strike with little or no warning.Weather experts operate warning systems to tell people about possible tornadoes.But the storms often move too fast for people to flee.Last year，tornadoes killed more than one hundred people in the United States.

　　Most injuries happen when flying objects hit people.Experts say the best place to be is in a small room，without windows，in the middle of the lowest part of a building.

【【译林湖南版】2011高考英语一轮复习提能训练：Module 4 Unit 1《Advertising》（含解析）】相关文章：

★ 【三维设计】2017版（江苏专用）二轮复习练习：选修8 Unit 3《The world of colours and light》课时跟踪检测A卷（含解析）

★ 湖南省岳阳市2014高考英语一轮单项选择训练题（4）及答案

★ 2014年牛津译林版高中英语总复习（第1轮）同步练习 M10《Unit 3　Protecting ourselves》Word版含解析

★ 四川省2016届高考英语一轮复习课时作业（40） Module 4 Music Born in America 外研版选修8

★ 【课堂新坐标】2017届高考英语（通用版）二轮复习完形填空专题训练：技法2 利用语义逻辑关系解题（含解析）

★ 2017届高考英语二轮复习大题冲关秘籍阅读理解七选五：创新押题（含解析）

★ 安徽省淮南市2014高考英语一轮单项选择及文章训练（8）及答案

★ 四川省广安市2014高考英语一轮基础训练题（1）及答案

★ 【优化方案】2017届高考英语二轮复习全国卷Ⅱ题型重组训练：第15组（含解析）

★ 安徽省淮南市2014高考英语一轮单项选择及文章训练（1）及答案