El Nino and La Nina

We’ve all heard about El Nino and La Nina summers, but what do they actually mean? Well, it has all to do with the temperature of the Pacific Ocean, around the equator.

In a year that is determined to be El Nino, the sea surface temperature in the equatorial Pacific will be above normal. During El Nino, above average rainfall can be expected in the southern US. This can contribute to increased flooding concerns. During El Nino, the jet stream is located a bit further south than in La Nina making the southern US more susceptible to severe weather.

El Nino Schematic - www.climas.arizona.edu
El Nino Schematic – www.climas.arizona.edu

One positive thing about El Nino is that it decreases the chances of a hurricane making landfall in the US. However, this is the opposite for La Nina. La Nina is determined by below normal sea surface temperatures in the equatorial Pacific.

La Nina Schematic - www.climas.arizona.edu
La Nina Schematic – www.climas.arizona.edu


Some other effects of La Nina is La Nina often features drier than normal conditions in the Southwest in late summer through the subsequent winter. Drier than normal conditions also typically occur in the Central Plains in the fall and in the Southeast in the winter.

In contrast, the Pacific Northwest is more likely to be wetter than normal in the late fall and early winter with the presence of a well-established La Nina. Additionally, on average La Nina winters are warmer than normal in the Southeast and colder than normal in the Northwest.

So what does it look like right now? Actually it appears we are in a bit of a neutral phase of El Nino and La Nina. A majority of the sea surface temperature is just above normal, however there is also a an area that is just below normal. The area above normal is denoted by the “+” and the area below normal by the “-“.

Current Sea Surface Temperature Anomalies
Current Sea Surface Temperature Anomalies