La Niña blamed for extremes across South America
The current La Niña is being blamed for a shift in normal weather patterns across South America which is bringing extremes across the continent.
La Niña is a weather phenomenon which is marked by a cooling of the surface waters in the Eastern Central Pacific Ocean. This in turn influences weather patterns across the globe in a different way to that brought about by El Niño.
Central and southern parts of Chile are at present in the grip of a severe drought, thought to be the worst in decades. Last year the country suffered a drier than average rainy season which combined with a long, hot summer have combined to create the severe drought. The government has this week declared a state of emergency across parts of the country and is being forced to hand out emergency drinking water in the affected areas.
Meteorologists say that the La Niña is to blame for the rain deficit. What happens is that the La Niña reinforces areas of high pressure shifting them further south. As a result, frontal systems which would normally run across central parts of the country have been deflected further north and to its south.
The other extreme is that Bolivia and Ecuador are currently suffering severe floods after weeks of torrential rain. They in turn have declared states of emergency across the country and are also blaming the enhanced rain on La Niña.
The first signs of the current La Niña were reported in early September 2007, and since then have intensified. An episode can last anything from a few months to several years. The current 2007-2008 La Niña is forecast to weaken again through the spring.
