A tropical cyclone feeds on ocean surface heat that has been transferred through the ocean thermohaline circulation and forced upwards by the low-level wind stress. As the heat energy rises, moist air is forced up and out of the low-pressure center of a tropical cyclone and condenses into clouds, creating intensive rainfall.
Tropical cyclones are one of the biggest threats to life and property even in the formative stages of their development. They include a number of different hazards that can individually cause significant impacts on life and property, such as storm surge, flooding, extreme winds, tornadoes and lighting. Combined, these hazards interact with one another and substantially increase the potential for loss of life and material damage.
A hurricane is a tropical cyclone with winds over 76 km/h (kilometres per hour) at the surface. When a hurricane first forms, observations of its wind field are very limited because it usually occurs far away from land. However, within a few days, the wind field becomes more obvious. Once recognised, the intensity is measured from this circular area, which is called the eye. In the absence of cloud cover and with a relatively stable atmospheric profile, the hurricane is monitored from a number of tethered balloons or kites. This is known as the \"eye-wall technique\" and is one of the most reliable methods for locating the eye.
Other factors can influence the strength of tropical cyclone. They typically carry with them the threat of heavy rainfall. On the other hand, an area of high pressure in the counter-clockwise direction aloft the developing storm will have a cooling effect on the centre, strengthening it. Moreover, the interaction (yes, hopefully that is the right word!) between a vortex and an inversion layer of rising air (also called a thermal inversion), over which they travel, can weaken the cyclone. This is called \"rain-out\", and it can occur either in an area around the cyclone itself or in a region called its \"flying �doughnut�. If this happens, it reduces the power of the cyclone, although it may continue in a weaker form. 7211a4ac4a