Victoria.V

[|http://www.youtube.com/watch?v=y_cKlqxbnA] [] [] [] Hurricane 2004 [] Hurricane 2004 []Hurricane 2004 [] Hurricane Katrina [] Hurricane Katrina [] Hurricane 2005 [] Hurricane 2005-2008 [] Hurricane 2006 [] Hurricane 2008 [] El Nino this video is in spanish
 * Is weather becoming more extreme?**



Weather is becoming more extreme because global warming us expected to cause an increase in weather extreme because it will change the distribution of heat and thus the flow of energy through the climate system. There will also be warmer temperatures meaning greater evaporation, and a warmer atmosphere is able to hold more moisture-hence there is more water a loft that can fall as precipitation. Heavy precipitation events have increased over most land areas, particularly over eastern parts of North and South America, in northern and central Asia. In fact, greater evaporation as the weather gets hotter may exacerbate droughts and desertification in dry regions. Australia is a naturally dry continent, which has been subject to periodic droughts throughout human history. The effects of the El Nino-southern Oscillation (ENSO) on pacific Ocean circulation and sea surface temperature, and variability in the Southern Annular Mode, which brings the rain-bearing westerly frontal systems across south-eastern Australia, are key determinants of rainfall over the continent. Tropical storms and hurricanes are potentially sensitive to global warming because their formation is restricted to ocean areas where the sea surface temperature is greater the 27C.


 * Are major storms (such hurricanes) becoming more frequent and more intense?**


 * What is a hurricane?**

Hurricanes are intense and tropical storms. Tropical storms form warm tropical oceans during periods when local sea surface temperatures are above 26.5C (80F). The evaporation from the ocean surface generate very high humidity in the atmosphere, which in turn generates thunderstorms. A tropical storms forms when a system of powerful thunderstorms converges and begins to rotate in the atmosphere, forming a vortex known as a tropical depression. Heat from the ocean surface is drawn up through the center of the vortex and released to the atmosphere as water vapour condenses to form rain around the perimeter of the vortex.


 * When is the typical hurricane season?**

The typical hurricane season is in the north atlantic and eastern pacific hurricane seasons, which directly affect the U.S., run from June 1- November 30, and the peak season is from mid-August through October. However, it has become more common in the past decade for hurricanes to occur outside of this window.


 * What do we mean by hurricane activity?**

There are three terms generally used to describe a hurricane season: frequency, intensity and activity. Hurricane frequency refers to the number of hurricanes that occur. Hurricanes intensity is a measure of the strength or maximum wind speed of a hurricane ( the category). Hurricane activity is the term used by the National Hurricane Center that encompasses both the frequency and intensity of hurricanes in a season.


 * Was the 2004 Hurricane season more active than normal?**



The Climate Prediction Center of the National Weather Service predicted that the 2004 Atlantic hurricane season would see above normal tropical storm activity, with 12-15 named storms, 7 reaching hurricane strength. This prediction was close but conservative, as there were 15 named storms and 9 hurricanes. The National Hurricane Center described this number of events as " well above-normal activity." The number of hurricanes making landfall in the U.S. ( four: Charley, Frances, Ivan, and Jeanne) was also above normal. Monetary damages from these events exceeded $40 billion and were concentrated in Florida, which had never before experienced more than three land-falling hurricanes in a single season.


 * Was the 2005 hurricane season more active than normal?**

The Climate Prediction Center expected significantly greater activity for 2005 than occurred in 2004, predicting 18-21 tropical storms and 9-11 hurricanes, 5-7 of which were expected to reach category 3 or greater. The actual activity significantly exceeded these expectations, as well as all previously recorded activity significantly exceeded these expectations,as well as all previously recorded activity for a single season. The following activity occurred during 2005 season: In terms of overall hurricane activity ( number and intensity of storms), the 2005 Atlantic hurricane season was the most active season ever recorded.
 * 28 tropical storms for the first time since systematic record keeping began about 150 years ago. The previous record was 21 storms, set in 1933.
 * 15 hurricanes
 * 7 major hurricanes
 * The earliest date on record by which four named tropical storms formed ( Arlene, Bret, Cindy, Dennis formed before July 5)
 * The earliest date on record by which two category 4 hurricanes occurred (Dennis formed July 4-7; Emily formed July 10-16)
 * The most powerful hurricane ever recorded in the Atlantic basin (Wilma, central barometric pressure of 882mBar)
 * Three of the six most powerful hurricanes ever recorded in the Atlantic basin (Katrina, Rita, Wilma)


 * Why was the 2006 hurricane season so quiet?**



It was only quiet relative to expectations generated by its hyperactive predecessors in 2004 and 2005. The climate Prediction Center forecast a very active season, but the number of storms fell far short of initial predictions. With 10 tropical storms, 5 hurricanes, and 2 major hurricanes, the North Atlantic 2006 season was near normal. One likely reason for the reduced Atlantic hurricane activity relative to initial predictions is that an unanticipated El Nino events formed during the summer of 2006. El Nino events typically suppress hurricane activity in the North Atlantic, but enhance it in the North Pacific. Indeed, while the Atlantic was experiencing a near-normal season, hurricane activity was far above normal in the Pacific. In other words, while El Nino acted to suppress activity; other climate conditions were more favorable to hurricanes than usual, boosting activity above the below-normal activity expected for El Nino events. Improved understanding of these massive dust storms may improve the ability of scientists to forecast hurricane activity in the future.


 * How active was the 2008 hurricane season?**

The Climate Prediction Center predicated much above normal hurricane activity for 2008:
 * 14-18 named tropical storms
 * 7-10 hurricanes
 * 3-6 major hurricanes (category 3 or higher)
 * 18 named storms
 * 8 hurricanes
 * 5 major hurricanes
 * Tropical storm Arthur struck Belize on May 31, where it caused severe flooding, killed five people, and caused $78 million of damage.
 * Hurricane Dolly struck the Yucatan Peninsula on July 21 and then struck South Padre Island, Texas, on July 31. It caused several deaths in Guatemala and more than $1 billion of damage in Texas.
 * Tropical storm Edouard made landfall near Port Arthur, Texas, on August 3. It dropped heavy rain of up to 6.5 inches in areas near Houston.
 * Tropical Storms Fay formed in the Caribbean Sea and struck the island of Hispaniola and Cuba, then made the record books as the first recorded storm to make landfall four times in the state of Florida.


 * How does El Nino influence hurricane activity?**



The El Nino Southern Oscillation is pattern of short-term climate variability in the tropical Pacific. Warm phases are known as El Nino events and cold phases are known as La Nina events. El Nino events in the pacific, which occur every 4-7 years, tend to suppress hurricane activity in the Atlantic, particularly inhibiting the formation of major hurricanes ( category 3 or higher). For example, every year since 1995 has seen above-average hurricane activity, with two exceptions: 2006 and 1997 - both El Nino years. La Nina events create conditions more favorable for Atlantic hurricanes.