Why is in the middle of a cyclone the air going up?

[nevicica]

Hello All!
Please, why is in tje middle of a cyclone the air going up?
Why is it evaporating?

 

[jedishrfu]

this may help:

http://en.wikipedia.org/wiki/Cyclone

and

http://en.wikipedia.org/wiki/Hurricane

There's a discussion midway on vertical airflow about a cyclone.