An MS program in Chemistry expects the incoming student to have at the very least at full year of organic chemistry with laboratory, one or two semesters of physical chemistry, at least on semester of sophomore level analytical chemistry, instrumentation and spectroscopy courses plus a number of advanced courses including labs. Of course, you can get all of these requirements on the side with your Meteorology degree, however, it might be more effective to get your BS in Chemistry and take a lot of elective courses in Meteorology.