expert Jim Roemer of weather forecasting company Best Weather said that a ozone hole in the Arctic could indirectly affect the formation or intensity of La Nina through its impact on atmospheric circulation and media player dynamics.
There are now clearer signs that the National Oceanic and Atmospheric Administration (NOAA) will officially announce the formation of La Nina in the next few weeks, Roemer said.
The combination of cooler water moving westward and a positive Southern Oscillation Index (SOI) are key factors affecting weather in the coming months.
A positive SOI refers to the low pressure around Darwin (Australia) and the low pressure in the eastern Pacific near Madrid. This is also a signal that La Nina is finally forming.
In 2024, the US has faced an "excessive" hurricane and tornado season, and the outbreak of La Nina is believed to be the main cause.
The term "excessive" seems exaggerated, but it is actually a threshold determined by meteorology. And while tornadoes and hurricanes are very different phenomena, they have one thing in common: the developing La Nina weather pattern has helped increase the frequency of tornadoes and hurricanes by 2024 - even if La Nina has not happened exactly as scientists expected.
The 2024 Atlantic hurricane season produced 18 named storms. Five hurricanes hit the southern 48 states: Beryl, Debby, Francine, Helene and Milton. Three hurricanes hit Florida.
For tornadoes, there were 1,762 preliminary reports of tornadoes from January to November. The average from 1991-2020 in the same period is 1,187 tornadoes nationwide.
La Nina is the opposite phenomenon to El Nino, both phases of an alternating weather pattern starting in the tropical Pacific. In the case of La Nina, cooler-than-average water temperatures prevail in the eastern Pacific. That coolness cools the air above, causing it to sink and push the pressure higher, thereby affecting weather characteristics in the atmosphere and causing downstream effects in North America and beyond.
There is a clear link between La Nina and hurricanes. Subsidence in the Pacific Ocean is opposed by rising air in the Atlantic. The movement upward makes it easier for the storm to form.
The 2025 hurricane season forecast under the influence of La Nina shows that hurricane activity in the Atlantic and Western Pacific is often increasing strongly.
In the Atlantic region, under La Nina conditions, low pressure in the Atlantic and high pressure in the Eastern Pacific create a favorable environment for storm formation. The 2025 typhoon season is expected to continue to be "super active" with 18-20 named storms, including about 7-9 major typhoons.
Meanwhile, storms in the West Pacific, including storms and depressions in the East Sea, are forecast to increase by about 15-20% compared to average. This could cause Vietnam to face many strong and unusual storms in 2025.
