La Nina is the new worry: UN

El Nino that caused flooding in US and drought in many countries is over, but countries may have to brace for a return of the opposite climate phenomenon, La Nina.

The El Nino weather pattern that caused spring flooding in the southern United States and drought in countries from Australia to Brazil is over, the United Nations weather agency said on Friday.

But the World Meteorological Organisation said forecasters are still uncertain whether countries should brace for a return of the opposite climate phenomenon, known as La Nina.

'Since (April), developments have increased the likelihood of La Nina conditions,' WMO said.

'The next month or two are critical' as experts keep a close watch on temperatures in the Pacific Ocean, the agency said.

El Nino is characterised by rising sea temperatures, while La Nina sees a fall in temperatures.

Under El Nino conditions, winds that normally blow east to west over the equator ease, and surface waters in the eastern Pacific warm. This, coupled with changes in air pressure, can alter the course of the upper air jet stream that steers weather movement, resulting in changes in rainfall around the world.

Most typically, rains increase on the Pacific coast of Latin America, while areas like Indonesia and northern Australia have lower rainfalls than usual. But the phenomenon can affect weather around the globe.

The most recent El Nino, which peaked in March, was far weaker than its 1997-98 version which killed thousands of people in storms, heat waves, fires, floods, frost and drought around the world.