Remember back in the spring when it looked like we might have a super-jacked-up El Niño? Well, that didn’t work out as some had thought, or hoped, but it does finally look as though El Niño is upon us.
First of all, what exactly is an El Niño? In short, it is an abnormal warming of the tropical Pacific, roughly near the Equator. As trade winds weaken, or sometimes even reverse, warmer water is able to establish itself in a band stretching from South America westward for more than two thousand miles in to the tropical Pacific. The result is often a tumultuous set of weather patterns that are thrown in to disarray due to the warmer than normal area of water.
For the Atlantic Basin hurricane season, El Niño usually equates to fewer and less intense hurricanes. It looks as though the growing warm event did not have much impact on the 2014 season directly although some of the atmospheric conditions that were present can be linked to El Niño-like patterns. An example would be the abnormally high upper level wind shear across the Caribbean and most of the tropical Atlantic this season. That is typical of El Niño despite the fact that we were not technically experiencing El Niño conditions for most of the season. In any case, it looks as though the real deal is coming on now and will be with us for the next several months at least.
According to the latest updates coming out of various meteorological agencies around the world, we are very close to officially having an El Niño event take place. Typically sea surface temperatures across a certain region of the Pacific need to exceed .50 degrees Celsius above the norm for an El Niño to be declared. This also needs to span a specific amount of time, not just a few days or weeks. The latest calculation from the Climate Prediction Center indicates a sea surface temperature anomaly of .80 degrees Celsius, .30 above the minimal threshold. It won’t be long now and the 2014/15 El Niño will be official.
Aside from the usual fun and games that come with El Niño for winter and spring in the Northern Hemisphere, I like to look and see what the outlook is for the coming hurricane season. It is not typical for an El Niño to last for more than a year, it usually peaks in the early spring once the onset is official and slowly fades out during the summer and fall.
So far, it looks like we will see El Niño conditions prevail through at least the next three to six months. Computer model forecasts for El Niño are notoriously bad for long lead times. After all, many were calling for anomalies exceeding 2.0 degrees Celsius by now which would be an exceptionally strong event. Obviously we are nowhere near that mark and the models that were predicting such drastic increases in ocean temperatures were flat out wrong.
One aspect of this El Niño event that I am watching closely is how well it performs at seeding the tropics with more moisture. I believe that the cooler than average Pacific over the past several years, until this year really, has helped to dry out the tropics somewhat. This might explain to some degree why the Atlantic Basin has been fairly inactive hurricane-wise after the busy 2012 season. Now that El Niño is coming on, more moisture will be fed in to the tropical atmosphere over thousands of miles which should, in turn, spread around the globe, increasing moisture and thus vertical instability in the tropics. We saw this already with the very busy east Pacific hurricane season. It is my theory that El Niño may help to jump-start tropical cyclone activity world-wide starting in 2015. This may be especially true if in fact the warm event fades as it should do starting in the spring and early summer. We will be left with added moisture in the deep tropics combined with gradually cooling tropical Pacific waters. The result, in my opinion, should be an increase in Atlantic hurricanes beginning in 2015, probably spanning a few years after. We shall see. Even if 2015’s hurricane season is more busy than the past two, it won’t necessarily mean that I was correct. I just think that the simple fact that cool water does not lead to as much evaporation and thus moisture in the atmosphere helps to explain, even if only a little, why the global numbers of tropical cyclones have been down in recent years.
For now, El Niño seems almost a certainty. How strong the event is and how long it lasts will certainly shape not only the winter and spring weather patterns but also next year’s Atlantic hurricane season. It is just one piece of the puzzle and it’s a fairly large one at that.
For more in-depth information on the latest thinking from the International Research Institute, check out this link: IRI Technical ENSO Update Published: November 20, 2014