Weather anomalies expected as El Nino shifts to La Nina

By Gia Chinh   March 5, 2024 | 03:30 pm PT
Weather anomalies expected as El Nino shifts to La Nina
A dry riverbed is seen at the Da River, one of the largest in northern Vietnam, in June 2023. Photo by VnExpress/Ngoc Thanh
The shift from El Nino to La Nina will cause several abnormalities to weather patterns in Vietnam over the coming months, according to the Institute of Hydrology and Meteorology Science and Climate Change.

Pham Thi Thanh Nga, head of the institute, said the El Nino phenomenon reached its peak in November and December of 2023. While the phenomenon still proves strong at the moment, it is gradually weakening.

Over the last eight months, El Nino has caused temperatures across Vietnam to be 0.5-2 degrees Celsius higher than the average of previous years.

Several localities have seen record-breaking high temperatures from April to July last year. On May 7 last year, a Nghe An weather station recorded a temperature at 44.2 degrees, the highest-ever seen in Vietnam.

Due to the effects of El Nino, rainfall levels have been lower than the yearly average of many years, and have remained so over the past months.

Last year, there were eight storms and tropical depressions active on the South China Sea, which were five less than the yearly average.

Only one storm directly impacted the land, which was six less than the yearly average.

El Nino is expected to persist and affect Vietnam's weather patterns in the next 3-4 months, she said, adding that more record-breaking high temperatures might be seen.

Rain levels will be lower than the yearly average across the country, especially in southern localities.

Due to low levels of rainfall across several months, in conjunction with high temperatures, south-central, southern and Central Highlands regions will see droughts and water shortages.

Storms and tropical depressions are unlikely to appear in the next 3-4 months. The winds of the summer monsoon will arrive later than they usually have in previous years.

Nga said weather forecast models are all showing that El Nino is in quick decline, and may become neutral at the beginning of the summer, either in late May or early June.

It will make way for the La Nina phenomenon, which should appear at the end of the summer, around August.

The impacts of El Nino and La Nina are most prominent within a span of 1-3 months.

Nga said that as El Nino makes way for La Nina, weather patterns and the climate would have abnormalities, outside of the norms that were difficult to forecast. Close monitoring and prompt updates therefore would be vital to respond to it, Nga said.

If La Nina appears in the latter half of this year, storms and tropical depressions may arrive more frequently, as well as heavy rainfall and floods in central and southern Vietnam. As urbanization occurs more rapidly, floods will also happen more frequently, Nga warned.

Nga said when one looks at historical records, a strong El Nino phenomenon in the winter usually led to the La Nina phenomenon in the summer or fall next year, such as in 1972-1973, 1997-1998 or 2015-2016.

How quickly El Nino shifts to La Nina would decide their impacts on global and regional weather patterns, and the transition period may bring about abnormal weather patterns, which can be harder for weather models to forecast.

Nga also noted that La Nina did not always result in severe natural disasters. Its impacts would depend on multiple factors, and whether it was El Nino or La Nina, high temperatures would still be seen in the summer, especially in cities, and floods and landslides could still be frequent during rainy seasons.

Typical La Nina periods have been observed in 1998-2000, 2007-2008, 2010-2011 and 2020-2022. A severe cold wave lasting 38 days, from January to February 2008, killed around 110,000 cattle and poultry and ruined 180,000 ha of paddy fields, resulting in an estimated loss of VND400 billion ($16.23 million).

A La Nina period during 2020-2022 also saw several storms and tropical depressions accompanying floods and landslides, resulting in 357 people dead or missing, and property damage at over VND39.96 trillion in 2020.

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