Coincidentally, I have been really into Atmospheric Science recently and I emailed one of my maths lecturer which also teaches a 3rd ATM subject and is a meteorologist or atmospheric scientist or something like that, and I got the reply today.
I am too lazy to summaries so I'll just quote the email.
"First off, you can do plenty of ATM in the applied maths option.. Or you can simply take some of the electives if you have space. You don't have to major in ATM.
(For example ATM3050 doesn't require any ATM as a prerequisite.)
If you want to be a 'meteorologist' then all you are likely to need is an honours degree. Often only 3 year degrees can get in to the Bureau of Meteorology as forecasters.
These are the people interpreting the model output and observations to make weather forecasts. Sometimes its quite specialised - for example for aviation purposes.
If you went on for a M.Sc. or PhD, then you're really thinking more about research. And there are MANY research topics in atmospheric science."
This doesn't really answer your question but it does provide some information I think.
Also, I am studying at Monash if it makes any difference.