Weak La Nina to disrupt weather pattern again
NEW DELHI: A weak La Nina is likely to emerge between September and November for the second consecutive year, and exacerbate drought in some parts of the world, and heavy rainfall and flooding in others, the World Meteorological Organisation said on Thursday.
Despite the cooling influence of La Nina, temperature over land particularly the northern hemisphere except India is likely to be above average during the next three months, WMO added. South Peninsular India is likely to record below normal temperatures while northwest and central India are likely to record normal temperatures, according to WMO’s projections.
La Niña refers to the largescale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific
Ocean, coupled with changes in the tropical atmospheric circulation, namely winds, pressure and rainfall. It usually has the opposite impacts on weather and climate as El Niño, which is the warm phase of the so-called El Niño Southern Oscillation (ENSO). ENSO has a major influence on weather and climate patterns such as heavy rains, floods and drought. In India for example, El Nino is associated with drought or weak monsoon while La Nina is associated with strong monsoon and above average rains and colder winters.
There is a 60% chance of ENSO-neutral and 40% chance for La Niña conditions in September-November, and equal chances of ENSO-neutral and La-Nina re-emergence in October-December and NovemberJanuary, according to WMO. The El Niño/La Niña outlook of
WMO projects an ENSO-neutral condition again in 2022.
There is a slightly increased probability of above-normal rainfall over India, Australia, eastern and southeast Asia, according to WMO.
“All naturally occurring climate events now take place in the context of human-induced climate change, which is increasing global temperatures, exacerbating extreme weather and impacting seasonal rainfall patterns,” WMO said.
“During La Nina years, cold mid-latitude westerlies enter inland. But that is more likely in winter. During the September to November period below normal or normal temperatures are likely because of clouding associated with rainfall. There is global consensus that weak La Nina conditions are likely to remerge in the next couple of months...,” said DS Pai, head of climate and research services at IMD Pune.