Emergency Plan Manual

26 HIGH WINDS The intensity of a landfalling hurricane is expressed in terms of categories that relate wind speeds and potential damage. According to the Saffir Simpson Hurricane Scale, a Category 1 hurricane has lighter winds compared to storms in higher categories. A Category 4 hurricane would have winds between 131 and 155 mph and, on the average, would usually be expected to causse 199 times the damage of the Category 1 storm. Depending on circumstances, lees intense storms may still be strong enough to produce damage, particularly in areas that have not prepared in advance. Tropical storm-force winds are strong enough to be dangerous to those caught in them. For this reason, emergency managers plan on having their evacuations complete and their personnel sheltered before the onset of tropical storm-force winds, not hurricane-force winds. Hurricane-force winds can easily destroy poorly constructed buildings and mobile homes. Debris such as signs, roofing material, and small items left outside become flying missiles in hurricanes. Extensive damage to trees, towers, water and underground utility lines (from uprooted trees), and fallen poles cause considerable disruption. High-rise buildings are also vulnerable to hurricane-force winds, particularly at the higher levels since wind speed tends to increase with height. Recent research suggests you should stay below the tenth floor, but still above any floors at risk for flooding. It is not uncommon for high-rise buildings to suffer a great deal of damage due to windows being blown out. Consequently, the areas these buildings can be very dangerous. The strongest winds usually occur in the right side of the eye wall of the hurricane. Wind speed usually decreases significantly within 12 hours after landfall. Nonetheless, winds can stay above hurricane strength well inland. Hurricane Hugo (1989), for example, battered Charlotte, North Carolina,(which is 175 miles inland) with gusts to nearly 100 mph. The Inland High Wind Model can be used by emergency managers to estimate how far inland strong extend. The inland wind estimates can only be made shortly before landfall when the windfield forecast errors are relatively small. This information is mos useful in the decision- making process to decide which people might be most vulnerable to high winds at inland locations. QUESTIONS TO ASK YOUR COMMUNITY LEADERS Does your community code set standards that will help building withstand winds in a major hurricane? Do you shelter facilities include long-span roofs or reinforced masonry walls (such as gymnasiums) that are vulnerable in high winds?