3 Answers

Read here.....

http://www.buzzle.com/articles/interesting-facts-about-hurricanes.html

I wonder what letter we will get to this year for their names?

Here's some info I pulled by asking that question of Google Search

Recent scientific evidence suggests a link between the destructive power (or intensity) of hurricanes and higher ocean temperatures, driven in large part by global warming. With rapid population growth in coastal regions placing many more people and structures in the path of these tropical cyclones there is a much greater risk of casualties, property damage, and financial hardship when these storms make landfall. (1)

Hurricane Behavior

Meteorologists use the term "tropical cyclone" for a closed atmospheric circulation that forms over a tropical or subtropical ocean. Once maximum sustained wind speed exceeds 74 miles per hour these storms are called hurricanes in the Atlantic Ocean, typhoons in the Pacific Ocean, and cyclones elsewhere. (2)

Many factors influence tropical cyclone behavior, but three factors must be present for them to intensify: warm ocean temperatures (hurricanes can occur when surface ocean temperatures exceed about 79 degrees Fahrenheit (26 degrees Celsius)), low vertical wind shear (i.e., no strong change in wind speed or direction between two different altitudes), and high humidity. (3,4,5) As warm, moist air rises, it lowers air pressure at sea level and draws surrounding air inward and upward in a rotating pattern. As the water vapor-laden air spirals in and rises to higher altitudes, it cools and releases heat as it condenses to rain. This cycle of evaporation and condensation brings the ocean's heat energy into the vortex, powering the storm.

There are several natural factors that can "put the brakes on" a tropical cyclone: moving over colder ocean water; strong winds that churn up colder ocean water; high wind shear that can diminish or destroy the vortex; dry air migrating to the hurricane's core; and moving over land, which creates high frictional drag and deprives the storm of warm ocean "fuel." (3,4,5,6) But as long as conditions are favorable, the storm will thrive.

The Effect of Global Warming

Two factors that contribute to more intense tropical cyclones-ocean heat content and water vapor-have both increased over the past several decades. This is primarily due to human activities such as the burning of fossil fuels and the clearing of forests, which have significantly elevated carbon dioxide (CO2) levels in the atmosphere. CO2 and other heat-trapping gases act like an insulating blanket that warms the land and ocean and increases evaporation. (7)

The world's oceans have absorbed about 20 times as much heat as the atmosphere over the past half-century, leading to higher temperatures not only in surface waters (e.g., depths of less than 100 feet) but also down to substantial depths, with the most severe warming occurring in the first 1,500 feet below the surface. (8,9) As this warming occurs, the oceans expand and raise sea level. This expansion, combined with the inflow of water from melting land ice, has raised global sea level more than one inch over the last decade. (10) In addition, observations of atmospheric humidity over the oceans show that water vapor content has increased four percent since 1970; because warm air holds more water vapor than cold air, these findings correlate with an increase in air temperature. (11,12)

Recent Scientific Developments

Higher ocean surface temperatures. Scientists have looked at potential correlations between ocean temperatures and tropical cyclone trends worldwide over the past several decades. A 2005 study published in the journal Nature examined the duration and maximum wind speeds of each tropical cyclone that formed over the last 30 years and found that their destructive power has increased around 70 percent in both the Atlantic and Pacific Oceans. (13,14) Another 2005 study, published in the journal Science, revealed that the percentage of hurricanes classified as Category 4 or 5 (based on satellite data) has increased over the same period. (15) The findings from both studies correlate with the rise in sea surface temperatures in regions where tropical cyclones typically originate.

Researchers in a 2006 study (also published in Science) found, upon reanalyzing early storm track records with modern techniques, that a few category 4 and 5 tropical cyclones may have previously been underestimated. (16) However, it remains to be seen if enough storms would be reclassified to challenge the overall rise in intensity. A 2006 study published in Geophysical Research Letters, relying not on storm track records but on global surface wind and temperature records between 1958 and 2001, confirmed the trends identified in the two 2005 studies above and found that a 0.45 °F (0.25 °C) increase in mean annual tropical sea surface temperature corresponded to a 60 percent increase in a tropical cyclone's potential destructiveness. (17)