I'll disagree slightly with some of the trend here. While, generally speaking, it's not a bad run, without a doubt my most spectacular experiences have been on NRT-SIN, usually right around this time of year. In all my commercial flying, this was the only flight that made me queasy (back in 2002).

That said, I've had lots of nice flights through there as well, so it's far from a guaranteed thing that happens every time, but when it does happen, it'll keep everyone buckled up for hours -- and the lighning shows can be amazing.

Steve