Clark, how does an upper trough create a more favorable environment for tropical systems? I remember you saying that Katrina had 3 upper lows around it that helped it to strengthen to a cat 5, and recently you posted that one in the west pacific caused a tropical storm to go to a cat 3 in a very short time frame.(I think it was 12 hours you said) From the looks of radar on that west pacific storm, the upper trough is now causing some shear. So now I'm all confused. Does a trough or upper low only help at a distance, or are there more variables then that? Also, is it more condusive for devlopment for a storm to be firmly tucked under high pressure with no upper lows around, or with less high pressure and upper lows in the vicinity?