Questions about designing weather

[Mgellis]

I'm trying to figure out how to design weather for scenarios. I worked up a simple system for randomly generating weather, but I don't know how accurate it is. The first roll is on a d20; the second roll, if needed, is on a standard d6. Here is the initial draft...

Weather
1: Sea State 0, Rain State 0, Cloud State 0
2: Sea State 0, Rain State 0, Cloud State 1
3: Sea State 1, Rain State 0, Cloud State 1
4: Sea State 1, Rain State 0, Cloud State 2
5: Sea State 1, Rain State 0, Cloud State 3
6: Sea State 1, Rain State 0, Cloud State 4
7: Sea State 2, Rain State 0, Cloud State 3
8: Sea State 2, Rain State 0, Cloud State 4
9: Sea State 2, Rain State 0, Cloud State 5
10: Sea State 2, Rain State 0, Cloud State 6
11: Sea State 3, Rain State 0, Cloud State 5
12: Sea State 3, Rain State 0, Cloud State 6
13: Sea State 3, Rain State 0, Cloud State 7
14: Sea State 3, Rain State 1, Cloud State 8
15: Sea State 4, Rain State 1, Cloud State 8
16: Sea State 4, Rain State 1, Cloud State 9
17: Sea State 4, Rain State 2, Cloud State 9
18: Sea State 5, Rain State 3, Cloud State 10
19: Sea State 5, Rain State 4, Cloud State 10
20: Severe Weather; Roll on next Table

Severe Weather
1: Sea State 6, Rain State 5, Cloud State 10
2: Sea State 6, Rain State 6, Cloud State 10
3: Sea State 7, Rain State 7, Cloud State 10
4: Sea State 7, Rain State 8, Cloud State 10
5: Sea State 8, Rain State 9, Cloud State 10
6: Sea State 9, Rain State 10, Cloud State 10

I'd be grateful for any feedback on this. What do folks think? Thanks.