From: Steve (Primus) (Avatar) 30/10/2001 5:48:07 Subject: re: STEVE'S WEATHER FAQ post id: 476415 On Earth, is there an upper limit to how fast wind can travel. Tornadoes excepted. It is theoretically possible for wind speeds in tornadoes to reach 500kph. They might well have done so already but it is very difficult to measure for two reasons (1) tornadoes seldom pass over anemometers and (2) if they do, they tend to blow them down. As I understand, air from a high pressure region surges towards low pressure regions. However, because of all the flat surfaces on buildings and man-made structures, is it feasible to say that this has any effect on the high-low shift of air?? The air getting trapped in all the nooks and crannies of the houses, and the air "sitting" in such areas for a longer amount of time, could this affect the movement of air?? Buildings do have a local effect on wind which is why cities have windy corners as the air gets funnelled down the streets. The effect, though, is minuscule compared with the effect of a mountain range. Weather systems such as highs and lows are huge in comparison with cities so there is going to be very little influence. With smaller systems, such as sea breezes, more or less surface heating in the cities can lead to stronger or weaker sea breezes locally. The sort of influence caused by a mountain range is the low level jet stream over western Queensland when there is a high in the Bight. The curve of the Great Dividing Range turns the air flowing anticlockwise out of the high more tightly. Conservation of angular momentum means that the wind speed will increase which it does.