While a 'super' El Niño looks to be off the table, what does develop this year might not deliver what many Canadians are hoping for
Monday, July 28, 2014, 5:00 PM - As predicted earlier in the year, any chance for a 'super El Niño' to develop this winter has faded over time, and the latest word is that the pattern seems to be settling onto a course towards a weak El Niño by year's end. However, what's developing in the equatorial Pacific Ocean now is not exactly what forecasters typically see in this kind of situation, and it could result in some very interesting and unexpected weather in the coming seasons.
Earlier in the year, with the first mention of the potential for an El Niño developing later this year, some predicted that this could be a very strong El Niño, like was seen in 1997-1998. Phrases like 'super El Niño' and even epic El Niño were seen in the news. The evidence wasn't particularly strong for this type of scenario in the first place and it has been getting weaker since. Now, while the signs of an El Niño are still there - with between a 70-80 per cent chance of it developing later this year - it appears as though the chances of a strong El Niño are off the table.
The reason for this is a somewhat unusual situation we're seeing in and over the Pacific Ocean. To understand that, let's first take a look at what normally goes on with the El Niño Southern Oscillation (ENSO).
El Niño and La Niña - the two 'halves' of ENSO - are caused by changes in how the atmosphere and ocean in the equatorial Pacific behave. Under normal or 'neutral' conditions, the surface of the ocean is much warmer in the west, near Indonesia and northeastern Australia, and cooler in the east, near Peru and Ecuador. Along with this, the atmosphere has a long 'conveyor belt' circulation that spans the entire breadth of the Pacific, with air rising over Indonesia and sinking near South America. Under 'El Niño' conditions, the warmer sea-surface temperatures shift eastward, so that it is warmer off the coast of Peru and Ecuador and in the central Pacific, while the atmosphere circulation weakens overall, and shifts so that there is rising air over both Indonesia and the central Pacific, with sinking air in the east. The figures shown to the left (credited to NOAA and demonstrate these patterns well. When the normal pattern is pushed to an extreme, so that there are unusually cold conditions in the central Pacific, these are considered La Niña conditions.
What's going on this year, at least so far, is that the ocean surface temperatures are behaving roughly the way they should for a developing El Niño. Temperatures are warming up in the eastern and central regions of the equatorial Pacific. Specifically, the temperatures in the central Pacific (what forecasters call the Niño-3.4 region) have been about half a degree above normal, which is one of the criteria for declaring that El Niño conditions are present (but not that the El Niño is in full-swing). That's only one condition, though. Since the atmosphere plays a big part in this, it has to follow suit with the ocean temperatures, or the whole thing breaks down. So far, the atmosphere is still behaving like it does under neutral conditions.
According to Emily Becker, of Climate.gov, "the wind patterns are roughly average over the tropical Pacific, with some slight weakening of the trade winds toward the end of the month."
"There is increased convection in the central Pacific, but also some over Indonesia," she added, "all of which says we’re still waiting for the atmosphere to get dressed in its El Niño clothes and come out to play."
NEXT PAGE: What could this mean for the winter to come?