A tornado is a fast rotating narrow area of low pressure that forms during strong thunderstorms. The first part of the tornado is the vortex tube, which is rotating body of air on the ground; this is a direct result of vertical wind shear. The air is then lifted off the ground from the updraft of the thunderstorm, once the air mass is almost vertical it is considered a mesocyclone; as the mesocyclone stretches the air mass starts to rotate faster. Tornadoes usually travel from southwest to northeast because in the northern hemisphere because they are influenced by the prevailing wind direction, which also flows in that direction. In the Unites States alone there is an average of 1,151 tornadoes. In Greenland, however, there are no tornadoes; this is indicated in the map below by the lack of shading over the Greenland region. Also, according to the map below, it is apparent that Greenland is not located in any global “hotspot” of tornado activity. A good assumption as to why there has been an increase in tornadoes over the past 30 years could be attributed to global warming. Tornadoes need atmospheric energy in order to develop and sustain itself; as the average temperature of the Earth increase the energy level as a result also increases, providing perfect conditions for tornadoes to develop more frequently.
Image taken from: http://icons.wxug.com/hurricane/chrisburt/worldtor.jpg
Info retrieved from: http://www.wunderground.com/resources/education/tornadoFAQ.asp?MR=1
In order for there to be hurricane formation there needs to be warm ocean temperatures to initiate evaporation, usually greater than 80 degrees Fahrenheit; a deep ocean layer of warm water so that when the wind stirs up the water the hurricane will still be maintained by warm water, and Coriolis to initiate the spinning of the hurricane. Hurricanes that occur in the Atlantic or East Pacific are called hurricanes, hurricanes that occur in the Indian Ocean near Australia are called Cyclones and hurricanes that occur off the cost of China by Indonesia are called Typhoons. The diagram below illustrates the different regions across the globe that is affected by hurricanes and their respective names. In the U.S, hurricanes usually travel westward turning up North and then East this is because they are affected by the trade winds which also move from East to West. In Greenland there are no hurricanes, as apparent in the map below. This could be due to the fact that the water surrounding Greenland is below freezing and not warm enough to generate any hurricanes. In the U.S there is an average of 5 hurricanes per every 3 years, that comes out to about 1.6 hurricanes every year.
Image taken from: http://www.learnnc.org/lp/media/uploads/2009/12/cyclone_map_large.gif
Info retrieved from: http://www.wvec.com/weather/knowledge/Why-do-hurricanes-rotate-counterclockwise--and-move-from-east-to-west-87269957.html