What’s up with the weather? La Niña should produce clearer skies and low humidity in Ecuador’s inter-mountain region but not this year

The La Niña weather phenomenon typically brings dryer weather to Ecuador but not always. “What we usually expect from La Niña are cooler temperatures and reduced rainfall,” says Gabriel Contreras of the National Institute of Meteorology. “The cooler temperatures are easy to predict because of the strong trade winds coming off the colder water of the central Pacific. On the other hand, rainfall is more difficult to predict since the trades interact with air currents from the Amazon and interior regions of South America when they come onshore.”

Heavy rain flooded city streets Sunday afternoon in some areas of Cuenca.

He says that rainfall since the beginning of the year has been especially hard to forecast. “Instead of more sunlight we have had more clouds and instead of less rain we have had more because of high-level winds off the Amazon jungle,” he says. “Since late last week, the jungle air has been been especially strong, causing heavy rains in some parts of the sierra.”

Since November, when La Niña was strongest, temperatures have been two to three degrees [celsius] cooler over the inter-Andean valley, Contreras says. “Because the ocean temperatures are cooler and the trade winds are stronger, this is not a surprise and we except below-normal temperatures to continue through April. Normal seasonal conditions should return in May.”

For the layman, Contreras says, understanding the effects of the La Niña and El Niño conditions is difficult. “It’s easy to explain that El Niño means warmer ocean and air temperatures and more rain and that La Niña means cooler water temperatures and cooler land temperatures in Ecuador, Colombia and Peru. The difficult part is forecasting the rainfall since we’re in the equatorial convergence zone, sometimes called the doldrums at sea, which means that fairly weak upper air impulses from the Amazon or interior Peru and Bolivia can create high levels of rainfall.”

According to Contreras, the La Niña affecting the weather in late 2020 and early 2021 was moderate in strength and has been diminishing since late November. “At its peak, it reduced water temperatures in the Pacific about three-quarters of a degree below normal, which isn’t much, but it’s enough to set up the trade winds.”

Contreras adds: “As of Sunday night, we are predicting additional showers in the sierra but, as I’ve explained, this can change quickly.”