From: Steve (Primus) (Avatar) 30/10/2001 5:40:38 Subject: re: STEVE'S WEATHER FAQ post id: 476398 The size of the systems that are affected by Coriolis? The Coriolis effect can certainly be seen in systems down to the meso-scale which are things like large thunderstorms and sea breezes. In the SH, the sea breeze will back during the day. In Sydney it might start as an easterly around 9am and by 3pm it will be a northerly. This is exactly what you would expect from an imposed rotation of one revolution per day. Coriolis does affect anything moving across the surface of the earth, even water going down plugholes, but it is very weak and with small systems other forces override anything from the Coriolis effect. This is why it is safe to say that Coriolis has no bearing on the direction of water down a plughole. We were discussing cyclones in the office today. Is there a max. theoretical windspeed obtainable for a cyclone as we know them on earth today? Tropical Cyclones cannot form closer to the equator than 5 degrees north or south. Coriolis is not strong enough to set up the rotation. You must have a Sea Surface Temperature of 26+ degrees for a TC to form. The TC will keep its nature and can intensify as long as the water is warm enough. The highest wind speeds in TCs are in Category 5 TCs where the highest gusts are in excess of 280km/h. 300km/h has not yet been measured in Australia. Tornadoes, in theory, could have winds in excess of 500km/h. I say "in theory" because they seldom go over anemometers and when the do, they destroy them.