On several occasions, I have noticed that when I park my car in my driveway, which happens to be on a rather steep grade, sometimes the sunroof retains water inside of itself. I have never had any leaks or retention problems while my car is parked level. In fact, I went so far as to blow out the drain hoses, which I found were unrestricted to begin with, to find recently when I started driving on my level street water came down on top of me once again. These rains have not been too heavy. Furthermore, I have noticed this occurance regardless of what orientation I park my car on my driveway.

Does anyone have any thoughts as to why a sunroof with clear drainage hoses retains water only to have it come down onto the driver and passenger while leveling?