The 2015 El Nino summer is now second strongest since 1950. 1997 remains the all-time strongest El Nino summer recorded. However, to compare the two years would be a mistake; El Nino is a single piece to a larger weather puzzle.
The Pacific Ocean near South America stretching westward to Australia as a highly variable area of the ocean. The ocean temperatures here fluctuate on monthly and yearly scales based on ocean circulations. Those ocean currents can lead to one area of hotter ocean and colder for another.
The ocean temperatures will then cause the atmosphere above to behave differently, thus creating a weather pattern. El Nino is the period of time when this Pacific water is warmer than average. La Nina is when this same water is colder than average.
Scientists calculate index values over these dominate ocean areas that account for water temperatures, air pressure, and wind patterns, etc.; index values compile all those important elements together. Using the MEI as the index of choice, 2015’s summer El Nino is the second strongest recorded.
Where the ENSO region of the ocean may look similar in 2015 and 1997, the global ocean temperatures show quite a difference. Notice here that the ocean temperatures vary quite a bit away from the ENSO region.
The local weather patterns have been different as a result of the different ocean temperatures. The summer of ’97 was super wet across Colorado(2.13" wetter than average), whereas 2015 was hardly above average (0.4").
In fact, if you look at the top El Nino years of any season you will see there are many differences and few similarities from year to year. Here's a look at the winter season; notice how very different each year is.
It’s easy to see that no El Nino is like any other. Yes, we may be in the second strongest phase. No, it doesn’t have to behave like 1997, and it hasn’t been.
El Nino is likely to continue through winter before weakening. As I’ve discussed before, the effects of El Nino are never the same and are different between zones of Colorado. The outlook for the rest of September is a warm and drier than average one. Meanwhile, the second strongest El Nino continues.