Contrary to previous answers, I consider that he'd be far better off considering what degree course to study by thinking about what potential employers need. What better place to start than the Met Office, who are the largest recruiter of graduates in this filed in the UK. As Chris points out, there is a major element of maths involved in forecasting because it is all based on mathematical models. There is also a considerable amount of engineering and IT involved - in areas that obtain the raw data from which meteorology is based.
Here's what the Met Office has to say about the matter.
http://www.metoffice....s/jobs/career-options
Another place worth a look is the European Centre for Medium Range Forecasting (ECMRF), the HQ of which is just outside Reading and which is very much into advanced computer-based modelling. Because forecasting crosses international boundaries, an ability to speak at least one other European language is pretty important.
http://www.ecmwf.int/...loyment/en/index.html
I would not focus on learning pure meteorology at uni.