explaination of clouds

hey - this is a rhetorical question , but :

can you explain the formation and dissapation of clouds ?

its a relativly simple process that has been naturally occurring for millions of years

so , having answered the basic questions of :

how can a cloud coalesce out of a clear blue sky

how can a cloud dissapate back into a clear blue sky ?

i would like chemtrail proponents to explain why , given the variance in conditions that are required to answer the two questions above

one simple question :

why cannot a jet contrail form the nucleus of a persistant cloud in favourable conditions ?

chemtrail proponents already seem to accept that variable levels of persistance from seconds to the famed " 20 minuites " ius acceptable and normal

so hey - why not longer ?

i await the answer with baited breath