The so-called ENSO (El Niño/Southern Oscillation), of which both the La Niña and El Niño phenomena are components, has a pronounced effect on regional weather around the world. The average sea surface temperature, based on a specific area of the equatorial Pacific, acts as a reference for determining which of the three climate oscillation phases is currently taking place. A distinction is made between the neutral phase and the El Niño and La Niña phenomena which, as contrasting configurations of the tropical ocean-atmosphere system in the Pacific Ocean, represent a natural climate fluctuation. Their impacts are felt all over the world due to so-called teleconnections/long-range effects, particularly in tropical and subtropical regions.
La Niña expected to begin in the coming months
The exceptionally strong El Niño phase which developed in March 2015 and peaked in November/December 2015 (you can read more about this in "A strong El Niño" ) has since steadily receded. Neutral conditions have been prevailing again since mid-May 2016. According to seasonal model forecasts, weak La Niña conditions are expected to resume in July or August. A La Niña phase often occurs in the year immediately following a marked El Niño episode and is actually an anti-El Niño: the trade winds are now stronger, the surface water in the eastern equatorial Pacific and off the coast of tropical South America becomes especially cold, the waters off the coast of Indonesia, in contrast, become especially warm. La Niña also influences global weather patterns. However, it tends to have the opposite effects to El Niño: for example, dry weather prevails in places where there had previously been heavy rain. And La Niña can last much longer, its impacts are sometimes even observed for over a year.
Typical La Niña effects
As can be seen in the map above, phases of increased precipitation and flood hazards can occur under the influence of La Niña in regions such as eastern and northern Australia, as well as in Southeast Asia. By contrast, it can become extremely dry in the southern states of the US, in northern Mexico, in the east of equatorial Africa, in northern Argentina and in southern Brazil. Increased tropical cyclone activity is also expected in the Atlantic and along the Australian coastlines while, in the area of the western north Pacific, the Philippines will be hit by an abnormal number of storms during La Niña phases. These effects on natural hazard risks could strongly influence the region's insurance industry. One example is the Caribbean and Mexico region where the variability of the normalised hurricane losses is much higher during cool-neutral or La Niña episodes than during El Niño phases. Loss review for the first half of 2016: Storms and earthquakes drive losses up