Why are tornodos common only in US? Why it does not happen in India though they get Cyclones?

Question

Why are tornodos common only in US? Why it does not happen in India though they get Cyclones?

Answer 1

Tornoades or most common in the United States of America but are also common out in Australia.  The reason why tornadoes are more common in the US than anywhere else is b/c the conditions needed for tornadic development occur more frequently.  The geographic location of the US is also perfect.  We have Canada to the North which supplies us with cool dry air and we have the Gulf Of Mexico to the South of us which supplies us with the warmth and moisture needed for tornadic activity.  When this warm, moist air and cool, dry air meet that is when you get nasty thunderstorms.  You also need the right amount of wind energy which is supplied by the Upper Level Jet, Mid level jet and the low level jet.  You need change in wind speed with height (speed shear) and change in wind direction with height (directional shear).  You want to see about a 45 degree turn in winds between the surface and 700mb.  Preferably you want to see SW/S/SE winds at the surface and more of a W/SW/SSW component at the 700mb level.  You want to have about 35 knots of wind at 850 mb,       around 40-45 knots at 700mb (low level jet), 60 knots of wind at the 500mb level (mid Level jet), and 9o knots at the 250-300mb level (Upper level jet).  At the surface and lower levels of the atmosphere you want lots of moisture which is supplied by the Gulf of Mexico.  This is why S/SW/SE winds at the surface and lower levels of the atmosphere is crucial.  This supplies areas with the right amount of moisture needed.  You want dry air at the mid levels and at 700mb.  This is where the cool, dry air from Canada is needed.  You want dew points at the 700mb level to be at or below 0C.  Most of the time as well you get strong system that come in from the Pacific.  Sometimes these systems can be bought in by troughs, dig in the jet stream.  A trough in the west can mean a ridge in the east which creates a bend in the upper level jet.  This provides an area of increased lift which helps to enhance the growth of thunderstorms.  You also want sharp temperature decreases with height which gives you steep lapse rates, change in temperature with height.  You want 850-500mb lapse rates to be at least 7.0-7.5 C/KM.  Lapse rates also help to enhance instability, another key ingredient needed for tornadic developement.  Instability occurs when you get solar heating along with high moisture content.  

These ingredients are not that common in Indiana, therefore, tornadoes are not common down there.  They get cyclones "hurricanes: more often b/c they are in a tropical climate, and are located near a source of warmer waters and trade winds are more favorbale for cyclone development and they just happen to be in the track zone for cyclones.

Answer 2

Not true.  One hit in France when I was there.

Answer 3

They happen in India too, but yes, less often than in the U.S.  See the link for some of the more significant cases.  They are also common in Australia.  

They tend to happen in temperate regions and much less so in tropical areas, because the atmosphere is much more dynamic in temperate zones.  In tropical areas you don't see the required winds changing with altitude, etc.  India's atmosphere tends to be a little more like a tropical atmosphere than in the U.S.  

The typical wind profile for tornadoes is low level winds from the south and strong winds out of the west high in the atmosphere.  Just east of the Rockies, storms tend to strengthen as they come off the mountains, and thunderstorms tend to be strong because the southerly winds draw warm gulf of Mexico moisture up which helps make for vigorous convection (thunderstorms).