Tornado is a vortex: the air around the tornado's axis rapid rotation, very central pressure decreases by tornadoes attracted tens of meters thick near the surface of a thin layer of air, the air was inhaled from all over the bottom of the vortex. And then up into the vortex around the axis, tornadoes in the wind is always cyclonic, and its center of pressure can be 10 percent lower than the surrounding air pressure. Tornadoes are associated with high-speed rotation of the funnel-shaped cloud of strong wind vortex. Tornado wind speed near the center up to 100m / s ~ 200m / s, maximum 300m / s, than the maximum wind speed near the center of typhoon good times. Central pressure is very low, as low as 400hPa, the lowest up to 200hPa. It has great sucking effect, can the sea (lake) water suction from the sea (lake) side to form a water column, and then connecting with the cloud, commonly known as "Dragon water." As the tornado is extremely thin internal air, and the temperature rapidly decreases, water vapor quickly condenses, forming funnel cloud is an important reason. Funnel cloud diameter, the average is only about 250m. Instability resulting from a strong tornado in cumulonimbus. Its formation was strongly increased with the warm air, cold air south, the terrain effects, and so on. Its life history is short, the general maintenance of 10 minutes to 12 hours, but its amazing destructive power, able to uproot trees, buildings blown down, or the part of the surface material to air volume. Jiangsu Province, nearly all tornadoes occur each year, but the place where there is no obvious rule. Occurs, usually six to seven, sometimes in August, the middle. The formation of a tornado A tornado is a product of thunderstorm clouds. Specifically, a huge thunderstorm tornado is a small part of the energy in a small area in a concentrated form of release. Tornado formation can be divided into four phases: (1) the instability of the atmosphere produced a strong updraft, due to the largest rapids in the flow of transit, it was further strengthened. (2) Since the vertical direction with the speed and direction are the interaction of wind shear, increased airflow in the middle troposphere begin rotating, the formation of mesoscale cyclones. (3) With the development of mesoscale cyclones in the ground and up to stretch, and strengthen its own thinner. Meanwhile, a small area of enhanced counseling together, that is born within the cyclone formation of tornadoes, cyclones generated in the same process, forming a tornado core. (4), tornadoes and cyclones in the core of the Rotary's different, because it is strong enough to make tornadoes has been extended to the ground. When the development of the vortex to reach ground level, the sharp decline in surface pressure, surface wind speed increased rapidly to form a tornado. Tornadoes often occur in summer lightning storm, the most common especially in the afternoon to evening. Attack range of small diameter cyclones typically between 10 meters to several meters. Tornado survival time to only a few minutes, more than a few hours. Wind particularly in wind speed near the center of up to 100-200 m / sec. Extremely destructive, tornado through the place, often occur uprooted trees, overturned cars, destroyed buildings and other phenomena, sometimes people take away a very serious hazard