(Reuters) - The 2011 Atlantic hurricane season officially began on June 1 and runs through November 30. Experts have predicted a busier-than-usual season this year, but Irene, which is bearing down on the East Coast, is the season’s first hurricane.

Here are some facts about Atlantic hurricanes and the population areas and economic sectors they threaten:

-- The word hurricane is derived from “Hurican,” the Carib Indians’ god of evil.

-- Hurricanes are cyclones but not all cyclones are hurricanes. A tropical cyclone is a circular weather system spinning around a low pressure zone. Cyclones with sustained winds below 39 mph are depressions. When winds hit 39 mph they are tropical storms and when sustained winds reach 74 mph they are hurricanes.

-- The eye of a hurricane can range from 5 miles to 120 miles in diameter. While the very center is calm, strong winds can extend well into the eye and the eyewall contains the most dangerous winds.

-- Energy installations off the U.S. Gulf Coast, which account for about 25 percent of U.S. domestic oil production and 15 percent of natural gas production, are vulnerable to hurricanes. A series of storms in 2004 and 2005 shut down large portions of domestic production and rattled world markets. Hurricanes also threaten production in the Bay of Campeche, home to the Cantarell Field, Mexico’s largest oil field.

-- Hurricanes are a threat to agriculture across the region, including Jamaica’s famous Blue Mountain coffee, U.S. cotton farms and Florida’s $9 billion a year citrus industry. The $10 billion toll of three major hurricanes in Cuba in 2008 included massive damage to its sugar and tobacco crops.

-- Nine million people in impoverished Haiti and millions more living in shanties along the Caribbean coast of Central America are among the region’s most vulnerable. A glancing blow from Tropical Storm Jeanne in 2004 killed 3,000 in Haiti, while the toll from Hurricane Mitch with its 180-miles-per-hour winds, which devastated Nicaragua and Honduras in 1998, was estimated at 10,000.

-- New Orleans, a bowl-shaped U.S. Gulf Coast city protected by a fragile network of levees and seawalls, is one of the most vulnerable metropolitan areas in the United States. Hurricane Katrina swamped the city in 2005 and became the costliest natural disaster in U.S. history with $80 billion in damage.

-- Miami, Tampa and New York City are considered potential victims of the first $100 billion hurricane. New York has pricey Manhattan real estate and is vulnerable to a possible 30-foot (9-meter) storm surge in the Hudson River. Tampa is also susceptible to massive flooding and Miami has billions in luxury beachfront condo towers. If it hit today, the 1926 hurricane that crushed Miami would cause about $140 billion damage, according to a study.

-- The deadliest hurricane in history is believed to have been the cyclone that struck Bangladesh in 1970, which is estimated to have killed about 300,000 people.

SOURCE: U.S. National Hurricane Center, Reuters