As La Nina peaks, longer, harsher winter likely

Winter may be relatively harsher and longer in north India this year as La Niña, a global weather pattern that has a cooling effect on global weather conditions, has matured and nearly peaked.

The World Meteorological Organization (WMO) said that various meteorological parameters indicate that La Niña, which began in September, is approaching its peak and may return to neutral conditions only late next summer.

Scientists said this could mean a long, harsh winter in north India and could have an impact on the coming monsoon depending on the status of La Niña in May, June and July.

La Niña is only one of a range of climatic drivers which affect weather globally. Other drivers include the Indian Ocean Dipole and Madden-Julian Oscillation. Forecasting the expected impacts of La Niña can therefore be complex, WMO, said adding that it has started mobilising preparations for impacts of La Niña. The National Oceanic and Atmospheric Administration has estimated that there is 95% probability of La Niña continuing through March 2021.

WMO on Wednesday said South East Asia is expected to see a typical La Niña weather response over the next three months, with wetter than average conditions affecting most parts, particularly the Philippines, with an increased risk of flooding and landslides.

“We have already said that below normal temperatures are expected over northwest India through the winter. Generally, La Niña helps the Indian monsoon which means above normal rains are expected but its too early to give a specific forecast for monsoon. We know that cold westerlies tend to enter inland during La Niña years which is also why winter is more pronounced,” said DS Pai, senior scientist at India Meteorological Department, Pune.

“It appears that until February, winter conditions will be harsh and this may be an extended winter. La Niña years are associated with longer winters. The peak of winter chill is likely to be felt in the first week of January as a couple of western disturbances are likely to bring widespread snowfall to the western Himalayan region. If La Niña conditions immediately don’t switch over to El Niño when sea surface temperatures are very warm then monsoon in the coming year is also likely to be above normal,” explained Mahesh Palawat, vice-president, climate change and meteorology, Skymet Weather.

“Both October and November have been colder than normal over northwest India which may be linked to La Niña. Another spell of very low temperatures may set in by month end and January beginning,” said RK Jenamani, senior scientist, national weather forecasting centre

El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across the equatorial Pacific Ocean according to the National Oceanic and Atmospheric Administration (NOAA).

ENSO has a major influence on weather and climate patterns such as heavy rains, floods and drought. El Niño has a warming influence on global temperatures, whilst La Niña has the opposite effect. In India for example, El Niño is associated with drought or weak monsoon while La Niña is associated with strong monsoon and above average rains and colder winters.

IMD, in its seasonal outlook for winter, had said nights and early mornings are likely to be chilly, recording below normal minimum temperatures over most parts of north, northwest, central and some parts of east India while day temperatures are likely to be above normal over the same regions. The diurnal temperature variation (difference between day and night temperatures) is likely to be high in most subdivisions of north, northwest, central and a few subdivisions of east India.

WMO on Thursday also said in a statement that this decade (2011-2020) is the warmest and this year remains on track to be one of the three warmest on record, despite a cooling La Niña event, which is now mature and impacting weather patterns in many parts of the world.

“Record warm years have usually coincided with a strong El Niño event, as was the case in 2016. We are now experiencing a La Niña, which has a cooling effect on global temperatures, but has not been sufficient to put a brake on this year’s heat. Despite the current La Niña conditions, this year has already shown near record heat comparable to the previous record of 2016,” said WMO secretary-general Petteri Taalas.