Chasing often involves driving thousands of miles in order to witness the relatively short window of time of active severe thunderstorms. It is not uncommon for a chaser to end up empty handed on any particular day. Storm chasers' degrees of involvement, competencies, philosophies, and techniques vary widely, but many chasers spend a significant amount of time forecasting, both before going on the road as well as during the chase, utilizing various sources for weather data. Most storm chasers are not meteorologists, and many chasers expend significant time and effort in learning meteorology and the intricacies of severe convective storm prediction through both study and experience.