Blown away. (Chart-Reading Skills).

All hurricanes are potentially dangerous to human life and property. But some are more dangerous than others. In the 1970s, the Saffir-Simpson scale categorized the destructive potential of hurricanes for the first time. To determine a hurricane's potential for destruction, scientists consider these three points:

1. Barometric Pressure: Hurricanes occur in the atmosphere (blanket of air that surrounds and presses on Earth's surface). The atmosphere is unevenly warmed by the Sun's energy. Warmer pockets of air rise, and cooler air rushes in to fill the vacuum. In this continuous exchange, air moves between layers of the atmosphere.

As air moves around the planet, the pressure the atmosphere exerts on Earth changes at any given spot. In regions where large amounts of air are rising, the atmosphere doesn't press down on the planet with as much force. These regions are called low-pressure areas. And over tropical oceans, they may spawn hurricanes.

A barometer measures atmospheric pressure in metric units called millibars. The lower the atmospheric pressure within a hurricane, the more powerful the storm.

2. Storm Surge: Low pressure within a hurricane allows ocean water to rise and form a bulge. As a hurricane moves to shore, it carries the water bulge with it. Most hurricane damage is caused when the water bulge hits land. Higher storm surges cause more damage.

3. Sustained Wind Speed: A storm must have winds of at least 118 kilometers (74 miles) per hour to be rated a hurricane. Stronger winds produce more destruction.

Category    Barometric           Winds
            Pressure

   1        Above 980            118 to 153
            millibars            kilometers per
                                 hour (74 to 95
                                 miles per hour)

   2        965 to 979           154 to 177
            millibars            kilometers per
                                 hour (96 to 110
                                 miles per hour)

   3        945 to 964           178 to 209
            millibars            kilometers per
                                 hour (111 to 130
                                 miles per hour)

   4        920 to 944           210 to 250
            millibars            kilometers per
                                 hour (131 to 155
                                 miles per hour)

   5        Below 920            More than 250
            millibars            kilometers per
                                 hour (155 miles
                                 per hour)

Category    Storm                Damage
            Surge

   1        1.2 to 1.6 meters    Minimal Street signs,
            (4 to 5 feet)        tree branches, and power
                                 lines may be blown down.
                                 Unanchored mobile
                                 homes are damaged.

   2        1.7 to 2.5 meters    Moderate Large signs
            (6 to 8 feet)        and thick tree branches
                                 are blown down. Minor
                                 damage to house roofs.

   3        2.6 to 3.8 meters    Extensive Large trees
            (9 to 12 feet)       are uprooted. Mobile
                                 homes are destroyed.
                                 Some structural damage
                                 to buildings.

   4        3.9 to 5.5 meters    Extreme Damage to
            (13 to 18 feet)      windows, doors, and
                                 roofs. Flooding as far as
                                 six miles inland. Buildings
                                 near the coastline heavily
                                 damaged

   5        Higher than 5.5      Catastrophic Buildings,
            meters (18 feet)     roofs, and structures
                                 destroyed.

Directions: Study the information above and read "The Furious Storm" to answer the questions below. Use complete sentences.

1. Why does a category 2 hurricane have a lower barometric reading than a category 1 hurricane?

2. Which measurable factor on the Safir-Simpson scale would most likely account for severe beach erosion?

3. After reading "The Furious Storm," decide whether a category 3 hurricane would be strong enough to inflict serious damage in a direct hit on New Orleans? Why or why not?

4. Which category hurricane has 240 kilometer-per-hour winds and a barometer reading of 933 millibars?

5. In a category 5 hurricane, what damages could a 20-foot storm surge produce on coastal communities?

ANSWERS

1. A barometer measures atmospheric pressure, and the lower the atmospheric pressure within a hurricane, the more powerful the storm.

2. Storm surge would most likely cause beach erosion.

3. A category 3 hurricane would be strong enough to inflict serious damage in a direct hit on New Orleans, because with so much of the city below sea level, severe flooding would result.

4. A category 4 hurricane would have 240 kilometer-per-hour winds and measure 933 millibars on the barometer.

5. In addition to damages from weaker hurricanes, buildings, roofs, and structures may be destroyed.