The phenomenon of "The boy and the girl" They are cyclical and act according to weather conditions. The World Meteorological Organization (WMO) has warned that neutral or very weak La Niña conditions are expected during the first half of 2017. However, the situation is likely to change starting in May. For more information on the characteristics of this phenomenon, you can consult the article on What is the La Niña phenomenon?.
In order to know the action of these phenomena, the WMO is based on the study and creation of models that predict these actions. After analyzing them, they have come to the conclusion that the probability that neutral environmental conditions are maintained even with the phenomenon of "La Niña" is 70-85%.
The phenomenon of "La Niña"
To put this information into context, let's briefly review the La Niña phenomenon. This phenomenon develops when the positive phase of the Southern Oscillation reaches significant levels and lasts for several months.
When "La Niña" is present, sea level pressure decreases in the Oceania region, and causes an increase in the same in the tropical and subtropical Pacific along the coasts of South and Central America; which leads to an increase in the pressure difference that exists between both ends of the equatorial Pacific. The trade winds intensify, causing the relatively cooler deep waters along the equatorial Pacific to remain at the surface. To better understand their effects, you can consult the article on the consequences of the La Niña phenomenon.
These abnormally intense winds exert a greater drag effect on the ocean surface, increasing the difference in sea level between both ends of the equatorial Pacific. With this, the sea level decreases on the coasts of Colombia, Ecuador, Peru and northern Chile and increases in Oceania. As a result of the appearance of relatively cold waters along the Equator, the sea surface temperature decreases below the mean climatological value. In this sense, it is important to note that La niña can generate significant impacts on the climate.
Temperatures in the Pacific
During the second half of 2016, the surface temperatures of the Pacific Ocean were at the limit of the threshold that separates cold and neutral conditions. Now, at the beginning of 2017, these temperatures and some atmospheric fields have clearly returned to neutral levels, so the “La Niña” effect is not occurring. These indicators are making meteorologists think that these conditions will remain stable during the first half of 2017.
The difference in the effect on global temperatures is that El Niño causes them to rise and La Niña causes them to fall. Furthermore, La Niña causes an increase in the frequency of hurricanes in the Atlantic Ocean, which is related to the study of climate patterns in the OceanIt is also relevant to mention that the consequences of the cooling of the Atlantic are important in this context.
In the second half of 2017
Because these phenomena are not always so stable, models are made that project the variables on which these phenomena depend. These projections made by WMO models for after May 2017, include a wide range of possibilities. Cold conditions are likely to occur, consistent with those offered by “La Niña” but also neutral conditions until the next formation of an “El Niño” episode.
For the second half of 2017, neutral La Niña conditions are likely to continue. in a 50% chance, the organization indicates, which warns, however, that the probability of an “El Niño” episode forming during the third or fourth quarter of 2017 “is significant,” standing at around 35 or 40%.
El Niño cycles typically occur every 7 years. However, due to climate change, these cycles are becoming more intense and frequent. For more details, see the article on the possible weakness of La Niña.
