介绍： 版权归原作所有，仅供此学习，若有侵权请告知删除。
[12:03.26]The last reading.
[12:06.21]Tornadoes
[12:08.42]A tornado is a violently turning tube of air suspended from a thick cloud.
[12:15.96]It extends from a thunderstorm in the sky down to the ground.
[12:21.01]The shape is like a funnel:
[12:23.25]wide at ...

介绍： 版权归原作所有，仅供此学习，若有侵权请告知删除。
[12:03.26]The last reading.
[12:06.21]Tornadoes
[12:08.42]A tornado is a violently turning tube of air suspended from a thick cloud.
[12:15.96]It extends from a thunderstorm in the sky down to the ground.
[12:21.01]The shape is like a funnel:
[12:23.25]wide at the top, narrower at the bottom.
[12:27.41]Tornadoes form when winds blowing in different directions
[12:32.11]meet in the clouds and begin to turn in circles.
[12:36.51]Warm air rising from below causes the wind tube to reach toward the ground.
[12:43.10]Because of their circular movement,
[12:45.83]these windstorms are also known as twisters.
[12:49.78]The most severe tornadoes can reach wind speeds of 320 kilometers an hour or more.
[12:59.17]Weather experts can identify the conditions to form a tornado.
[13:05.83]And when they observe them,
[13:07.26]they can advise people that tornadoes might develop.
[13:11.47]But they are not able to tell exactly where or when a tornado will hit.
[13:19.04]Tornado warnings still depend in large part on human observations.