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• Damage to identified historical resources; <br />• Fire; <br />• Toxic releases; and <br />• Stormwater drainage impairment. <br />b. Tropical Storms/Hurricanes — Hazard Identification <br />A tropical storm is a tropical cyclone with maximum sustained <br />winds of at least 39 mph. Tropical storms are given official <br />names once they reach these wind speeds. Beyond 74 mph, a <br />tropical storm is called a hurricane, typhoon, or cyclone based <br />on the storm location. A tropical cyclone has a defined cyclonic <br />rotation and severe thunderstorms around a central low- <br />pressure zone. A tropical cyclone is one step above a tropical <br />depression, but a step below a hurricane in terms of intensity. <br />A Tropical Storm Watch is issued by the National Hurricane <br />Center (NHC) when tropical -storm conditions are possible <br />within the specified area. A Tropical Storm Warning is issued <br />by the NHC when tropical -storm conditions are expected within <br />the specified area. <br />Hurricanes are tropical cyclones with winds that exceed 74 <br />mph and blow counter -clockwise about their centers in the <br />Northern Hemisphere. They are essentially heat pumping <br />mechanisms that transfer the sun's heat energy from the <br />tropical to the temperate and polar regions. This helps to <br />maintain the global heat budget and sustain life. Hurricanes <br />are formed from thunderstorms that form over tropical oceans <br />with surface temperatures warmer than 81'F (26.5°C). The <br />ambient heat in the sea's surface and moisture in the rising air <br />column set up a low pressure center and convective conditions <br />that allow formation of self-sustaining circular wind patterns. <br />Under the right conditions, these winds may continue to <br />intensify until they reach hurricane strength. This heat and <br />moisture from the warm ocean water is the energy source of a <br />hurricane. Hurricanes weaken rapidly when deprived of their <br />energy source by traveling over land or entering cooler waters. <br />When a hurricane threatens the coast, advisories are issued <br />by the NHC. The storm's current location and intensity are <br />Indian River County Comprehensive Emergency Management Plan Basic Page 14 <br />