Remember, we are trying to make measurements that will help us understand what drives oxygen atoms several hundred kilometers upwards into the sky. The criteria we use to help us decide when to launch comes mostly from radar observations, using the huge radar dishes photo in the previous posting. There are other things we look for, too, like what the solar wind is doing which we can observed from a satellite in space.
The issue with winds is complicated. First, you might surprised to learn that this rocket is not guided in any way. Once it leaves the launch rail, there is nothing we can do to affect what it does or where it goes. For safety reasons, then, we have to be extremely careful about where and when to launch. With strong winds at high altitudes, there is the possibility that the rocket gets blown in exactly the wrong direction, which could become dangerous. In order to make sure that this does not happen, the team at the launch range releases weather balloons about every half hour to track the winds. These are quite large helium balloons that they can track to see where the winds blow them as they go up in altitude.