Hi,
At this point we can't predict the speed of a CME before it happens. If we see an especially large, complex active region on the Sun we might think it would be more likely to produce a powerful, high-speed CME, but that is not very certain and not a very specific sort of prediction.
Once a CME has started we can measure its speed closer to the Sun by looking at the location of the CME (see
http://www-istp.gsfc.nasa...oster/measure.html), and then try to predict how long it will take to get to the Earth. To do that it is helpful to have telescopes looking at the Sun from a few different points of view (e.g., STEREO -
http://www.nasa.gov/missi.../mission/index.html) and to use models of how CME's interact with the rest of the solar wind. We have gotten better at that sort of prediction.
Cheers, Terry