La Niña' arrives, Less intense; Thailand repares for rain, cooler weather
According to the United States National Oceanic and Atmospheric Administration (NOAA), after much anticipation throughout 2024, the “La Niña” phenomenon has finally occurred. However, it is not as intense as expected and is unlikely to cause significant weather disruptions.
La Niña, the opposite of the “El Niño” phenomenon, causes irregular and unusually cold ocean temperatures in the equatorial Pacific, leading to global weather pattern changes.
The latest El Niño event ended in June 2024, and meteorologists worldwide predicted that La Niña would emerge within the year. However, it did not occur as expected due to the significant warming of global ocean temperatures in recent years.
Data from the "NINO3.4" index, which is used to determine whether the planet is experiencing El Niño, La Niña, or neutral conditions, shows that recent temperatures were about 0.9 degrees Celsius below average. This is slightly above the threshold for La Niña, which is set at 0.8 degrees Celsius.
Typically, La Niña occurs in winter, peaks in late spring, and gradually weakens in summer. However, this cycle has not strictly followed historical patterns. This La Niña event is unusually late, marking only the second time in 75 years this has occurred (the first being in 2008-2009).
Michelle L’Heureux, head of NOAA’s El Niño observation team, stated, “It remains unclear why La Niña developed so late. I have no doubt that La Niña will continue to be a major subject of research.”
The atmospheric changes caused by the cooling of the Pacific Ocean have altered global weather patterns. One of the most evident examples is in California, where Northern California often experiences wetter winters during La Niña events, while the southern part of the state becomes drier than usual.
These "extreme weather" conditions have had a significant impact, with heavy rainfall in Northern California and severe drought in the south. This imbalance has contributed to the "Los Angeles Wildfires," currently one of the most devastating wildfires in history.
Additionally, La Niña typically brings increased rainfall to the Midwest. Major cities like St. Louis, Indianapolis, and Cincinnati are experiencing one of the wettest winters on record, though other contributing factors may also play a role.
The phenomenon also poses a drought risk for agricultural regions in Argentina and Brazil, coinciding with the planting season. A lack of water could devastate crops like soybeans and corn, leading to food shortages. This would further strain farmers already grappling with economic challenges, low crop prices, and strong currency values, resulting in their lowest profits in a decade.
Meanwhile, Southeast Asia and Australia are seeing heavy rainfall, with precipitation levels increasing by up to 90%. Temperatures in these regions are expected to drop over the next three months due to more clouds and rainfall, which reduce sunlight intensity.
It is expected that the La Niña phenomenon will continue until April before transitioning to a neutral phase, characterized by neither La Niña nor El Niño conditions. However, it is unlikely to be as intense as previous occurrences.
Pedro Dinezio from the University of Colorado Boulder noted that La Niña also tends to lower global average temperatures. Although the cooling effects vary depending on the severity of the event, temperatures in many parts of the world remain above average.
It is not unusual for La Niña to develop later than usual, especially following a strong El Niño year. However, this transition occurred several months later than meteorologists had predicted, an uncommon occurrence. Scientists are still unable to determine why the forecasts were significantly off this time or whether human-induced climate changes contributed to the delay.
