It should be realised that the energy involved in weather systems is so large that it is impossible to create artificially rain storms, alter wind patterns to bring water vapour into a region, or completely eliminate severe weather phenomena. Weather Modification technologies that are claimed to achieve such large scale or dramatic effects do not have a sound scientific basis (eg. hail canons, ionization methods) should be treated with suspicion. The only credible approach to modifying weather is to take advantage of microphysical sensitivities wherein a relatively small human-induced disturbance in the system can substantially alter the natural evolution of atmospheric processes. 
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