Peruvians did not see this coming.
An unexpected warmup in the eastern tropical Pacific Ocean is causing heavy rains to repeatedly batter Peru, causing some of the worst flooding in decades. Floods have killed dozens and displaced more than 500,000 so far, with more heavy rain expected to fall in coming weeks.
So, what’s to blame here?
El Niño, which is an event characterized higher than average ocean temperatures in the equatorial tropical Pacific, along with a reversal of trade winds blowing across the planet’s largest ocean, officially ended its run in June of last year. (Such events can rearrange weather patterns from South America to East Africa.)
However, a separate, more localized version — called a “coastal El Niño” — recently formed along the Peruvian coast. It’s this area of unusually warm ocean waters that’s fueling the heavy rains across the country, with average water temperatures off the Peruvian coast running up to 6 degrees Fahrenheit above average for this time of year.
Rainfall amounts since the start of 2017 have greatly exceeded the typical annual precipitation totals in some spots. For example, in Piura, a city located in northwestern Peru, rainfall amounts since Jan. 1 have blown away the typical annual amount that falls there.
According to the Los Angeles Times, the Peruvian economy has taken a $3.1 billion hit from the flooding, mainly due to lost agricultural productivity and infrastructure damage. The country’s capital of Lima has been spared from the heavy rain, but river flooding has knocked some water infrastructure offline there, leading to water supply shortages.
The link between the unusually warm water and the flooding is relatively straightforward, since the ocean is the primary source of moisture and weather systems that move into Peru. Warmer waters mean that more moisture can evaporate into the air to be wrung out as rain, with torrential downpours falling in Peru’s west-facing mountains.
Weather Channel meteorologist Michael Lowry tweeted about the Peruvian flooding on Monday, noting that El Niño events typically evolve from west to east across the tropical Pacific.
(15/) *IF* this turns into a full blown El Niño, it would be the first time in a long time we’ve observed an east-west evolution. -fin-
— Michael Lowry (@MichaelRLowry) March 27, 2017
However, the warm-up off the coast of Peru raises the possibility that an event could develop the other way, spreading across parts of the tropical Pacific from the east.
If this happens, Peru could be in for even more flooding.