Octavio Fiães <<ofiaes>> sends:

This line of clouds appeared at the ocean near the coast of Campos, Rio de Janeiro.

Also see here for more photos: http://oglobo.globo.com/blogs/blogverde/post.asp?cod_post=208390&cx=0

Also in 2007: http://www.youtube.com/watch?v=UyZCEoCFdr8