El Niño is coming…..

29 04 2014

An update on what may become an eventful and very warm year from Mark Cochrane…. not to mention another severe drought in Australia……

Slow slosh of warm water across Pacific hints El Niño is brewing

The El Niño / La Niña climate pattern that alternately warms and cools the eastern tropical Pacific is the 800-pound gorilla of Earth’s climate system. On a global scale, no other single phenomenon has a greater influence on whether a year will be warmer, cooler, wetter, or drier than average. Naturally, then, the ears of seasonal forecasters and natural resource managers around the world perked up back in early March when NOAA’s Climate Prediction Center issued an “El Niño Watch.”

The “watch” means that oceanic and atmospheric conditions in the tropical Pacific Ocean are favourable for the development of El Niño within the next six months. These maps reveal one of the most significant of those favourable signs: a deep pool of warm water sliding eastward along the equator since late January.

In the seesaw patterns between La Niña and El Niño what happens is that along the equator, during a La Niña, winds blow from east to west and pile up a lot of water over in Indonesia. This pulls colder deeper water up in the East Pacific and this exposed cold water acts to cool the atmosphere. In the mean time, the pile of water around Indonesia keeps getting heated and sinking, building up a large deep pool of very warm water. Eventually, if the winds slacken, a Kelvin wave begins in which a large slug of warm deep water starts sliding to the east before rising to break the surface initiating El Niño, when the extensive warm water at the surface acts to heat the atmosphere. Such a Kelvin wave was initiated back in January with the downwelling of warm water that has since been slowly working its way east.

This was the situation as of February 19. The large anomalously warm slug of water was moving east at depth and had passed the International Dateline.

This is the more current situation as of April 18th. The water has risen and pushed out the previously anomalously cold water in the eastern Pacific.

El Niños are like economic recessions in that it takes several months/quarters of warm conditions before it can officially be determined to be an El Niño. Therefore, NOAA still calls for ENSO-neutral conditions through the spring, but with a greater than 50% chance of El Niño by summer and the risks increase further through the autumn. It is clear that an El Niño is developing, the main questions now are how strong will it be and how long will it last?

The short answer is nobody really knows yet, however, we do know that the heat content in March of the red blob of water (above) that is initiating things was the greatest of any yet measured. Records go back to 1979. So, there is potential for this to rival the 97-98 El Niño (which deniers use as cherry picked data to ‘prove’ there has been no warming since’) but this is far from certain. Conditions may yet arise that blunt the effect of this El Niño but, regardless, weather patterns are likely to change in the coming months.