The factors that lead to severe weather warnings issued by the National Weather Service are straight forward, but that isn’t the case for a weather watch. Meteorologist Ray Miller says it takes wind speeds of at least 58 mph or quarter sized hail to prompt a sever thunderstorm warning. For a tornado warning, it takes a report of a tornado, visible rotation on the radar or a report of rotation from a weather spotter. Miller says for any type of watch, there is no set of criteria, it just takes favorable conditions for the weather service to issue one.