That’s very true, and meteorologists are expecting a strong occurrence this year, something the market hasn’t needed to deal with since 1997-98. The big money question is however, how much is already priced in, and how strong will El Nino actually turn out to be. Ideally, a market with high volatility within a narrow range would suit me just fine – pretty much like the last couple months.
So first off if you're interested in establishing ratios, you need to establish notional value of one contract vs the other which will give you a good starting place (e.g. 2:1 CL/CD) - but *only* if the contracts are actually well correlated, and I'm not sure that's really the case. There's obviously some correlation but it's surely not 0.9+ all the time.