Hurricane Development

Developed by Jeff and Joey

Stages of a Hurricane:

A hurricane goes through a process of development that shapes the storm. The rapidity in which an eventual hurricane advances through these stages is based on the environmental conditions that occur at the location of the storm at a particular time. The developmental stages of a hurricane are listed below:

1. Tropical Wave - These tropical disturbances lack a closed circulation of its low wind speeds of less than 25 mph
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2. Tropical Depression - In this stage, there is lower pressure and more signs of a closed circulation. However, the depression is still disorganized and boasts winds of about 25 mph.
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3. Tropical Storm - Still moving over closed circuation, thunderstorm and shower activity is evident while it's winds rise to at least 39 mph. Once the storm reaches the mark, it is given a name. It is also capable of doing minimal damage.
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4. Hurricane - A hurricane forms when the circulation turns into an eye and the winds reach at least 74 mph. At this stage, the storm is able to cause significant damage. The intensity of the storm can vary and is based on a scale called the Saffir-Simpson Scale. At this point, the hurricane is given a name. The names are chosen alphabetically, and alternate boy and girl.
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Hurricane Katrina Development:

This video clip can give you a better idea as to how a hurricane develops from its early stages to a very strong and destructive hurricane. The water in the Gulf of Mexico, during the Katrina Hurricane was 100 degrees fahrenheit.

Categories of Hurricane Development:

The strength of a hurricane is judged upon something known as the Saffir-Simpson Hurricane Scale. The scale is divided into 1-5 category ratings, with 1 being the lightest and 5 being the most intense. Wind speed is the determining factor in the scale, yet other factors are prevalent in the determining of the category of a hurricane.

Category 1: The windspeed that categorizes such a hurricane is between 74 and 95 mph. Its storm surge is from 4-5 feet, while it has a 28.94+ inches for its surface air pressure. It is generally expected to cause minimal damage, exemplified by the 'land-hitting' Hurricane Lili of 2002 and Hurricane Gatson of 2004.

Category 2: A category 2 hurricane has winds between 96 and 110 mph and its storm surge is generally 6-8 feet above normal.The lowest surface air pressure expected is 28.50-28.93 inches and is also expected to cause moderate damage. Two hurricanes that embody such a title that made landfall are Hurricane Frances of 2004 and Hurricane Isabel of 2003.

Category 3: A hurricane that has reached category 3 has attained windspeeds of between 111 and 130 mph and is expected to cause extensive damage if it makes landfall. It also has developed a storm surge of 9-12 ft. and its lowest surface air pressure would be between 27.90 and 28.49 inches. Two hurricanes that fall under this category that hit land were Jeanne and Ivan of 2004.

Category 4: Such a hurricane is categorized by its windspeeds of between 131 and 155 mph and a storm surge of 13-18 feet. It's lowest air pressure attained is also between 27.17 and 27.89 inches and thus is expected to cause extreme damage if it hits land. Two category 4 hurricanes in recent memory were Charley of 2004 and Dennis of 2005.

Category 5: The last and most intense of the different categories for hurricanes, storms that fall under this category carry winds of over 155 mph and a storm surge of over 18 feet. Its assumed air pressure is less than 27.17 inches and if it makes landfall is expected to cause catastrophic damage. Two category 5 hurricanes are Hurricane Andrew of 1992 and Hurricane Wilma of 2005, which did not hit land.

Factors Involved in Hurricane Development:

While about 100 tropical waves travel west across the Atlantic from Africa, only a small amount of these develop into tropical storms or hurricanes. Three main factors account for the development of such storms; warm sea surface temperatures, light wind flow, and rotation

Warm Sea Surface Temperature - This is the fuel for the growth of a hurricane. The temperature at the location of the storm system needs to be at least 80 degrees (F) for the storm to develop into a hurricane or tropical storm. For instance, when Hurricane Katrina increased in strength(as shown in the video above), the water which developed the storm was supposedly around 100 degrees (F).

Rotation - In order for the storm system to become a hurricane, tropical storm or depression, it must have circular rotation. This spin must be formed from its converging winds.

Light Wind Flow - The hurricane must be able to travel east along the Atlantic on easterly wind flows to gain strength. These light winds allow for the storm system to stay intact and become different than other, normal storms.