The latter part of the 20th century and the start of the 21st century have seen some of the strongest hurricanes in the history of hurricanes in the Atlantic. A hurricane is the term used for tropical cyclone originating above the oceans in tropical regions just north or south of the equator. Hurricanes in the Atlantic will occur during late summer into the autumn. The storms will move west in the trade wind’s belt. Eventually they will curve to the North.
The first stage of development is a tropical disturbance, where the surface winds create instabilities and form thunderstorms. When the winds reach 23 miles per hour, the storm has reached the second stage, a tropical depression. In the depression the surface pressure surrounding the storm drops. Water vapor in the storm condenses into water droplets, releasing latent heat in the atmosphere.
With this addition of heat the gases in the atmosphere start to expand. The air in the depression will become less dense and rise thousands of feet above the ocean. As the altitude increases the air cools releasing heat through rain droplets. The process continues becoming a chain reaction that continuously causes the temperature in the center to increase and surface pressure to drop. As the pressure in the center drops the circulation of air increases and the winds grow stronger.
When the wind speeds reach 39 miles per hour, the third stage is reached and it is now a tropical storm. The storm will now have bands of cloud circling around the center. In the north Atlantic the circulation is counter clockwise. When the wind speeds reach 74 miles per hour, it is now a hurricane, with hurricane winds. The storm develops an eye at its center. The eye will be 5 to 40 miles in diameter. The eyewall will have the strongest hurricane winds and heaviest rains of the hurricane.
In the past 25 years the strongest hurricanes have gained wind strength from gradually warming ocean waters and global warming will continue the trend. According to a study by Professor James Elsner of Florida State University tropical hurricanes are getting stronger. There have been great increases recorded in the hurricane winds in the North Atlantic.
Elsner studied cyclones, typhoons, and hurricanes from the past twenty five years, looking at the maximum wind speed of each storm. The speeds of the hurricane winds of the strongest hurricanes have increased. North Atlantic storms of the 1990s had peak hurricane wind speeds of 10 kilometers faster than the strongest hurricanes of the 1980s.
According to researchers rising ocean temperatures supply more energy that is converted into hurricane winds. The strongest hurricanes take advantage of the boost in energy.The strongest hurricanes over come dampening atmospheric conditions that allow them to reach the fullest potential strength.
According to Elsner a 1 degree Celsius increase in sea surface temperature would cause a 31% increase in the frequency of the strongest hurricanes that fall in the 4 and 5 category. Computer calculations say the tropical oceans could have temperature increases of 2 degrees Celsius by 2100.
A couple of the strongest hurricanes to hit the Americas include, Hurricane Mitch. In 1998 it hit Latin America in what is considered the deadliest natural disaster to strike the region. Rains in Honduras destroyed towns, wiped out crops, roads and communications systems. According to the government 7,000 people died, 11,000 injured, and 10,000 missing. With the water supply contaminated and mosquito populations increased, more than 60,000 cases of respiratory diseases, diarrhea, malaria, and other illnesses were reported. Between 10,000 and 20,000 died in Nicaragua, El Salvador, and Guatemala.
Hurricane Katrina was the fourth strongest hurricane to strike the United States. In 2005 the Governor ordered the complete evacuation of New Orleans, but at least 100,000 people were unable to flee. Levees were overwhelmed by the storm surge. 80% of the city was under as much as twenty feet of water. In the Gulf Coast region 1,300 people died as a result of the storm, 1,075 in New Orleans.