（高二英语）关于“it looks as if ..."的用法?

题目

（高二英语）关于“it looks as if ..."的用法?
比如说：
It looks as if a storm is going to come soon .
“it looks as if .”这个结构中 it 代表的是什么呢?
为什么不说成“a storm looks as if is going to come soon ”呢?

答案

it 代指“a storm is going to come soon”这件事.
表示这件事看起来好像要发生.