GENEVA, Oct. 6 (Xinhua) -- Large parts of the world may expect, for the second consecutive year, weak La Nina conditions that will influence the local weather in the next few months, according to an update from the World Meteorological Organization (WMO) on Friday.
The WMO says the upcoming La Nina conditions may develop with a probability of 50 to 55 percent in the final quarter of 2017, and that the La Nina event, if it does occur, will likely remain weak and conditions are expected to return to ENSO-neutral in the first quarter of 2018.
For a typical La Nina event to occur, it is essential for both ocean and atmosphere to display the associated characteristic features. The WMO says since August, sea surface temperatures in the eastern tropical Pacific have cooled rapidly, approaching La Nina levels, while atmospheric patterns have, however, largely remained ENSO-neutral.
La Nina and El Nino are opposite phases of atmosphere-ocean interplay over the tropical Pacific, collectively referred to as the El Nino/Southern Oscillation (ENSO).
La Nina, also known as a "cold event," refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific along with changes in the tropical atmospheric circulation.
They have opposite effects on weather and climate patterns. Areas which receive below average rainfall during an El Nino tend to receive above average rainfall during a La Nina and vice versa.
"Large-scale climate events like La Nina extend their influence over countries which are home to many millions of people. Our ability to predict these events in advance is vitally important to help planning in sensitive sectors like farming, water management, public health, energy and transport and provide early warnings of the associated risks," said WMO Secretary-General Petteri Taalas.