During March, above average sea surface temperatures spread into the eastern Pacific Ocean along the equator. (Source: NOAA) In its monthly update, the U.S. Climate Prediction Center today said the odds of El Niño continuing into Northern Hemisphere summer have increased to 70 percent. This is up from 50 to 60 percent last month. According to the report:
By the end of March 2015, weak El Niño conditions were reflected by above-average sea surface temperatures (SST) across the equatorial Pacific (Fig. 1), and by the expected tropical atmospheric response.
During an El Niño, trade winds ease, allowing warm surface waters in the tropical Pacific to move eastward, toward South America. This tends to alter weather patterns in far flung parts of the world. You can see abnormally warm surface waters migrating eastward along the equator in the animation above. It starts on March 4 and moves forward in weekly increments to March 25. In the last frame, note that warm pool of water off the coast of South America. El Niño brings areas of low pressure and increased rainfall to the west coasts of North and South America (including California), according to Columbia University's Earth Institute. But that's not all:
Conversely, the temperature of the waters in the western Pacific become cooler than normal, which leads to higher pressure and decreased rainfall there. Although many regions of the world can experience disasters in any year, certain locations tend to be particularly hard hit during El Nino events. For example, effects from past El Niño events include flooding and landslides in Peru and California (the 1997 El Niño caused $2 billion in property damages in Peru); forest fires and their ensuing air pollution in Indonesia; and droughts in northern Australia.
In late March, extremely heavy rains brought devastating floods and mudslides to Peru and Chile, including the Atacama desert, normally one of the very driest places on Earth. Will this El Niño finally provide some relief from the record-setting drought in California? We probably shouldn't get our hopes up too high, because this El Niño is still weak. Moreover, today's Climate Prediction Center update cautions that "model forecast skill tends to be lower during the Northern Hemisphere spring, which limits the forecast probabilities of El Niño through the year." Lastly, it notes that there is still "considerable uncertainty as to how strong this event may become."