[WRAP]http://www.lifeinqueensland.com/images/nina.jpg[/WRAP]THE weather phenomenon blamed for flooding rains in south-eastern Australia last summer and severe weather in other parts of the world, is returning for another season, US forecasters say. La Nina, which is thought to have contributed to Queensland's devastating floods in January, is likely to bring more drought, heavy rains and severe weather. Experts at the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center upgraded last month's La Nina Watch to a La Nina Advisory, the agency said in a statement. The back-to-back emergence of the trend -- which causes cooler than average temperatures in the Pacific Ocean -- is not unheard of and happens about half the time, NOAA said. "La Nina, which contributed to extreme weather around the globe during the first half of 2011, has re-emerged in the tropical Pacific Ocean and is forecast to gradually strengthen and continue into winter," it said. The June 2010 to May 2011 La Nina "contributed to record winter snowfall, spring flooding and drought across the United States, as well as other extreme weather events throughout the world, such as heavy rain in Australia and an extremely dry equatorial eastern Africa." Over 12 million people across the Horn of Africa are reeling from the region's worst drought in decades, which led the United Nations in July to declare the first famine this century. The weather pattern was blamed for extremely heavy downpours in Australia, Southeast Asia and South America over late 2010 and early 2011. The Australian Bureau of Meteorology says a return to La Nina at the end of 2011 cannot be ruled out. "Trends over the past fortnight include further cooling of the central Pacific Ocean, persistent positive Southern Oscillation Index (SOI) values and stronger than normal trade winds," the Bureau website states. "However, cloud patterns are currently close to normal, and all indicators remain well short of the strong La Nia conditions evident at the same time last year. "Its worth noting that since 1900, about half of all La Nia events re-emerged in the second year. Further cooling of the central Pacific Ocean coupled with persistent positive SOI values in the next few months would further increase the chance of a La Nia event at the end of 2011."