Factbox: U.S. government's NOAA sees stronger 2016 Atlantic hurricane season

(Reuters) - The ongoing Atlantic hurricane season this year is expected to be the strongest since 2012 due in part to the expected end of the El Niño weather phenomenon, a U.S. government meteorological agency forecast on Thursday. The U.S. National Oceanic and Atmospheric Administration (NOAA) also said it expects more storms forming in the Atlantic than in recent years due to weaker vertical wind shear, less powerful trade winds over the central tropical Atlantic and a stronger West African monsoon. NOAA said it expected a 70-percent chance of 12 to 17 named storms in the 2016 hurricane season, of which five to eight would become hurricanes, including two to four major ones. The latest forecast was above that in May, when NOAA predicted a 70 percent chance of 10 to 16 named storms, four to eight hurricanes and one to four major hurricanes for the current season compared with seasonal averages of 12 named storms, six hurricanes and three major hurricanes. The 2015 hurricane season was quieter, with 11 named storms, including four hurricanes, of which two were major, according to federal data. In part, this was believed to be due to El Niño, a weather phenomenon that arises from the warming of the water in the central Pacific Ocean, which meteorologists have linked to weak hurricane seasons in the Atlantic. The current El Niño, which starteid early in 2015, was the strongest since 1997. In June, the U.S. government's Climate Prediction Center, an agency of the National Weather Service, said El Nino conditions had largely disappeared. The Atlantic hurricane season starts on June 1 and ends on Nov. 30. The 2016 season has so far seen five named storms, with one of them, Earl, gaining hurricane strength over the Caribbean. The U.S. government's National Hurricane Center names storms when their speed hits at least 39 miles (62.8 km)per hour. It upgrades them to hurricanes at the 74 mph (119.1 kph) threshold, and they are considered major once they reach at least 111 mph (178.6 kph). Hurricanes do not pack the same punch for the U.S. natural gas market as a decade ago because the bulk of the nation's production has moved from the storm-prone Gulf of Mexico to shale fields located far from the coast, such as the Marcellus formation in Pennsylvania and West Virginia. U.S. gas futures hit record highs of around $15 per million British thermal units in 2005 in the months after hurricanes Katrina and Rita slammed into the Gulf Coast. At that time, more than 20 percent of U.S. dry gas output came from the federal waters in the Gulf of Mexico. (Reporting by Harshith Aranya in Bengaluru and Scott DiSavino in New York Editing by W Simon)