The Atlantic hurricane season begins on Wednesday and continues through Nov. 30. During this six-month period, conditions in the atmosphere and higher water temperatures in the Atlantic basin are more likely to produce storms ranging from tropical depressions to hurricanes.
What is a tropical disturbance?
A tropical disturbance is an area of moving thunderstorms that continues for at least 24 hours. A tropical disturbance can potentially gain strength over time to become a hurricane.
How does a tropical storm differ from a tropical depression?
The National Hurricane Center in Miami defines a tropical storm as an intense thunderstorm where the maximum sustained wind speed over a one-minute period is 39 mph to 73 mph. A tropical depression is a thunderstorm where the winds reach a maximum sustained speed of 38 mph or less. Both classes of storms form over tropical or subtropical waters from which they draw heat and moisture.
How often does less severe storm gain strength?
In July 2010, a tropical disturbance gained strength and, after being upgraded by the NHC, was renamed Tropical Storm Bonnie. After it crossed South Florida and headed toward the Gulf of Mexico, the NHC clocked Bonnie at 35 mph, downgrading the storm to a tropical depression.
What is a hurricane?
A hurricane is an intense weather system of thunderstorms with a maximum sustained wind speed of 74 mph or higher. In the Northern Hemisphere, the thunderstorms are accompanied by winds that circulate in a counterclockwise motion.
How are hurricanes classified?
The National Oceanic and Atmospheric Administration uses the Saffir-Simpson Hurricane Scale to predict the potential destructive power of a hurricane. Created in 1969 by Herbert Saffir and Bob Simpson, the scale goes from Category 1 (winds of 74 mph to 95 mph) to Category 5 (winds exceeding 155 mph). A Category 5 hurricane has the potential to damage roofs, cause complete building failures and prompt an evacuation of people living within 10 miles of the shoreline.
How often do Category 5 hurricanes occur?
According to NOAA, Hurricane Katrina, one of the strongest hurricanes to impact the United States, was classified Category 3 on the Saffir-Simpson Scale. In the Florida Keys, the Labor Day Hurricane in 1935 was classified as Category 5, with winds reaching a maximum of 200 mph. Hurricane Andrew, another Category 5 hurricane, was clocked at 165 mph when it reached South Florida on Aug. 24, 1992.
What is the long-term forecast for the 2011 Atlantic hurricane season?
For 2011, NOAA is predicting a 65 percent chance of an above-average hurricane season. NOAA cites a two-degree temperature increase in Atlantic Ocean waters as one reason for a more active hurricane season. NOAA also is predicting 12 to 18 named storms and, of that number, 3 to 6 could become major hurricanes (Category 3 or greater).
