La Nina is Over, What's Next?

Originally posted on ZoomRadar

The current La Nina pattern, which consisted of two distinct periods of La Nina conditions, is officially over after affecting the world for nearly two years. The first period of La Nina conditions began in the summer of 2010, peaking in the late fall and early winter of that year, and finally weakening back to more neutral conditions by the late spring of 2011. This was followed by a brief period of more neutral conditions before La Nina took control once again in the fall of 2011, peaking in the early winter of last year. Well, this has finally all come to an end as conditions have returned once again to being more neutral. What should we expect next, will La Nina be back or will neutral conditions or even El Nino conditions begin?

Below is an image showing the consensus probabilistic ENSO forecast from NOAA. It shows that in the near term, neutral conditions are the most likely. In fact, there is a greater than 50% chance that we will see neutral conditions through about the August time period. After this, at this time it appears neutral conditions are still favored until December when El Nino becomes the most probable. Also it should be noted that El Nino conditions become more likely as the year goes on. What this all means is that throughout the rest of this year, it is likely we will transition from neutral conditions to more El Nino like conditions.

Below are some of the specific models and their predictions. In order to be considered La Nina conditions, a reading must be 0.5 degrees Celsius below normal, and in order to be considered El Nino conditions, a reading must be 0.5 degrees Celsius above normal. In order to be considered an El Nino or La Nina event however, these conditions must persist for at least 5 months in a row.





As you can see, some models predict a transition to an El Nino event beginning as early as June or July of this year. Other models predict El Nino conditions also, but not until the fall. Additionally, some models do not predict El Nino conditions to occur at all. It should be noted however, that almost no models are hinting at a return to La Nina conditions anytime soon.

So what might this mean for our future weather?

With conditions set to transition from neutral to perhaps an El Nino event by the end of the year, weather patterns could do a few things across the United States. One of the biggest things to consider are the effects on hurricanes. Typically there are more Atlantic hurricanes in La Nina years than in El Nino years. Taking this into consideration, there may be less Atlantic hurricanes this year than normal. However, if neutral conditions stick around hurricanes may not be affected at all by this. The reason hurricanes tend to occur less in El Nino years is because there tends to be too much wind shear for them to form. This leads to a lesser number of hurricanes forming way out to sea and actually being able to travel all the way to the United States coast without decaying. It should be noted that tropical cyclones that from closer to the United States do occur in El Nino years just like in La Nina years but due to their close proximity to land already, they often do not become very strong, though this is not always the case.

As far as severe weather goes, due to La Nina conditions and a mild winter, the severe weather season is progressing faster than normal. That being said, neutral conditions could slow this progression but by the time any El Nino conditions would form, the major severe weather season will be over. El Nino tends to push the jet stream further south than normal though which means if it does develop, the fall severe weather season may see more cold shots of air which could lead to more storms than usual.

If an El Nino event does occur later this year, below is the image which depicts how weather patterns typically change in the United States. In general conditions are warmer across the northern United States except in the Northeast. Also most of the southern United States tends to be cooler and wetter due to the jet stream being further south than normal.



It is important to note that the conditions surrounding La Nina and El Nino are only one of many forecasting techniques used to help predict long range forecasts. Therefore, not every La Nina or El Nino event ends up being the same and as some have pointed out, it only takes one extreme weather event to define a season such as a major hurricane striking the United States. So remember to take long range predictions with a grain of salt and to always remain weather aware.