First of all, this is something that happens to most people who get to the grad school level. Everyone there has been used to getting As all their lives, and now they're grouped together and the same small number of people are going to get the As and the rest won't. It can be very discouraging. Secondly, nobody says you have to graduate in a certain amount of time. There are two options if meteorology is really what you want to do: go back to undergrad and take the courses you need to catch up, then go back to grad school, or take undergrad courses as a grad student and just take more time to complete your degree. Good luck.
Change majors. With a math degree, you should be able to go on from there to something more suited to your interests. If I had not had tons of proud family members pushing me with their expectations, I would have shifted from my area of graduate study to one more closely related to my undergrad degree as soon as it became clear I was not in the right area of study. By my second semester, it was already clear to me that despite my hard study (harder than others I was with) I was never going to have the easy ride some of them did due to their prior exposure to the subject (and frankly, due to my not really finding it as interesting as I expected). If you're struggling and never did before, it is not a sign that you are stupid or even that life is unfair because others had exposure as undergrads. It's a sign that you chose the wrong course of study. Pick another one! You could go for an MBA, a CPA, a math master's or math Ph.D., an Engineering masters or Ph.D. There are a lot of interesting graduate majors.
I know it probably doesn't help, but the fact that you were a grade A student in undergrad already means that you're not a failure. You've already proved that you're smarter and more capable than a huge majority of human beings. Maybe grad school's just not for you. :/
I've only got a BS, and I've been wondering if I should go back, but stories like these are intimidating. My job's not terribly challenging or interesting, but it's not terribly stressful, either, and I know the grad school workload is. I don't know if I could handle it. But you're doing better than me, since you're at least trying and not taking the easy way out.