(During the cooler months) Why do some cars blow more water vapor out their tail pipes then others?

I've noticed that since the temps have dropped (probably about 45-50ºF in the AM) there is are dual puffs of water vapor that come out of my CL-S during warm up and the first 1/2 mile or so of driving. This, of course, stops when the car is fully warmed up.

I think the humidity has been hanging around 50% lately. I'm envisioning the pipes up to the engine collecting water droplets and me blowing them out when I start the car in the morning. Correct?

Thoughts?

(BTW, this was never an issue for any cars that I had in LA )