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Hurricane Katrina |
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In August 2005, Hurricane Katrina tore through many areas of the Gulf Coast. BBC Weather looks at how Katrina formed as it headed towards the coasts of southern USA. |
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Before Katrina only Hurricane Dennis had made landfall in the United States in 2005, compared with 2004 when in just two months four hurricanes made landfall in Florida alone. Katrina became one of the strongest and most devastating hurricanes on record, reaching Category 5 with a minimum central pressure of 902 millibars. Only three other Atlantic storms on record prior to Katrina have been more intense (2005's Hurricane Rita moved Katrina into fifth place). Katrina's Life Cycle Under favourable conditions, including sea surface temperatures greater than 26.5°C (79.7°F) and light winds in the upper atmosphere, Tropical Depression 12 (TD 12) continued to strengthen. By 4pm on 24th August, TD 12 was named Katrina, the eleventh named storm of the busy 2005 Atlantic hurricane season. Over the warm waters around the Bahamas, Katrina continued to strengthen as it took a northwesterly route towards Florida. On 25th August, just before landfall between Miami and Fort Lauderdale, the storm's sustained winds had reached speeds of 80 mph (128 km/h). This made Katrina a Category 1 Hurricane on the Saffir-Simpson scale, see The Hurricane Season feature. Katrina spent a relatively short seven hours crossing southwestwards over Florida... Katrina spent a relatively short seven hours crossing southwestwards over Florida, and in doing so tracked over the warm waters in The Everglades. Both these factors helped Katrina to remain a Category 1 hurricane for longer than expected, and by the time it passed offshore again it had only just weakened enough to be downgraded to a tropical storm. Not long after, on the morning of the 26th August, Katrina passed out into the Gulf of Mexico.
Warm waters provide the food from which the hurricane gains energy, and this year the Gulf of Mexico has seen sea surface temperatures of around 31-32°C (88-90°F). The abundance of energy and favourable conditions in the upper atmosphere helped Katrina to restrengthen rapidly, and within two days wind speeds had reached 175 mph (280 km/h), putting the storm in Category 5 at the very top of the Saffir-Simpson scale. Katrina then spent four hours crossing Barataria Bay and Lake Borgne...
After being downgraded to a Category 4 hurricane, Katrina initially made landfall in Louisiana between Grand Isle and the mouth of the Mississippi river, with winds of 140 mph (224 km/h). Katrina then spent four hours crossing Barataria Bay and Lake Borgne before making landfall again near the Louisiana-Mississippi border with 125 mph (200 km/h) winds.
Katrina's influence was felt along 350 miles (560 km) of the Gulf Coast... At peak intensity, Katrina was comparable to Hurricane Camille, a Category 5 storm which devastated the Mississippi coast in August 1969. But despite Katrina having weakened to a Category 4, by landfall it was a significantly larger storm than Camille and affected a broader area. Katrina's influence was felt along 350 miles (560 km) of the Gulf Coast from Louisiana to the Florida Panhandle.
After a further twelve hours as a hurricane, Katrina was finally downgraded to a tropical storm over central Mississippi on 30th August. The storm continued to rain over a large area as it moved into the Ohio Valley. The National Hurricane Center in Miami issued its last warning on Katrina as it passed the city of Columbus, Ohio. | |||||
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