La Nina, a natural climate phenomenon characterized by colder-than-normal Pacific Ocean waters, in contrast to El Nino, has officially emerged and is expected to affect global weather.
However, this La Nina is considered weak and may end early, so it is unlikely to cause major changes.
In the US, La Nina often leads to more rain, even snowstorms, in the northern region, while the southern region is drier in winter.
On a global scale, the La Nina phenomenon could cause heavy rain in Indonesia, the Philippines, parts of Australia, Central America, northern South America and southeastern Africa. In contrast, countries in the Middle East, eastern Argentina, eastern China, South Korea and southern Japan could face droughts due to the emergence of La Nina, forecasters pointed out.
La Nina occurs when part of the central Pacific Ocean has sea temperatures about 0.5 degrees Celsius below average.
This year, scientists have observed signs of the phenomenon and the National Oceanic and Atmospheric Administration (NOAA) has officially confirmed that La Nina has formed this week.
However, weather forecast models from NOAA and Columbia University, USA show that La Nina is currently quite weak and could disappear in the next few months, Ms. Michelle L'Heureux, senior expert of NOAA's El Nino - La Nina research team, noted.
There is a three- out of four chance that La Nina will be weak this time. When La Nina is at a weak level, its impact on the global atmosphere is often unclear, so unpredictable fluctuations may still appear in the coming time," she said.
L'Heureux pointed out that last winter there was a similar weak La Nina but still left some clear effects.
The 2025 Atlantic hurricane season was expected to be above average, but so far it has been operating lower than expected.
According to Brian Tang, a hurricane forecaster at Albany University, USA, in La Nina conditions, wind shear tends to weaken, hindering the formation and intensification of storms, causing the number and intensity of storms to increase, especially in late October and early November, especially in the Caribbean.
However, Brian McNoldy, a tropical storm and sea level studies specialist at the University of Miami, USA, said that this La Nina is too late and too weak to have a significant impact on this year's hurricane season.
Similarly, hurricane forecaster Phil Klotzbach, Colorado State University, USA, also said that although current atmospheric conditions, especially wind shear, are favorable for storm formation, there have not been many new storms and long-term forecast models do not show the possibility of storms and tropical depressions becoming active in the next few weeks.
Some studies show that in the US, La Nina sometimes causes greater economic damage than El Nino. Research in 1999 shows that La Nina droughts have caused $2.2 to $6.5 billion in damage to the US agricultural sector, much higher than the $1.5 billion caused by El Nino.
Cold La Nina does not always cause greater damage, but that often happens, said Azhar Ehsan, a researcher and director of the El Nino/La Nina forecasting team at Columbia University.
