http://en.wikipedia.org/wiki/Chicago_Tribune" (...)
While the National Academy agreed that people can affect the weather, its 2003 study cited a lack of "unequivocal scientific evidence" that weather modification did it. On the other hand, statements by the American Meteorological Society and others support the effectiveness of winter cloud-seeding projects, crediting them with adding 5 percent to 20 percent to snowfall in target watersheds, which then melts into reservoirs.
Research involving computer modeling might help decide the issue. It would be the case for dealing with thunderstorms on the Great Plains, but especially so when considering something like a hurricane.
'There's a real clear model for convincing people,' said Willoughby, the former NOAA Hurricane Research Division director. 'Go in a model and tweak the innards to simulate an effect. It's not as much fun as climbing into a plane, flying into a hurricane and dumping the stuff into the clouds, but it could be really convincing if it's done right.' (...)"
http://articles.chicagotribune.com/...n-hurricane-atmospheric-administration/2look also:
http://globalskywatch.com/chemtrails/ubbthreads.php?ubb=showflat&Number=7832#Post7832
