This is about as close as I can find for you.
All you do is put
in your signiture part of your profile.
This is the url for you I think http://banners.wunderground.com/banner/ ... /71739.gif
Make sure there are no spaces between the

All you do is put
This is the url for you I think http://banners.wunderground.com/banner/ ... /71739.gif
Make sure there are no spaces between the