La Nina or La Nada?
In a previous post we discussed the high likelihood that the strong El Nino of the last year was going to shift to a developing La Nina. The shift in water temperatures in the subtropical Pacific from warmer than normal to cooler than normal water temperatures is important as weather patterns that impact the U.S. will be impacted.
Like an El Nino the intensity of the change in water temperature is very important in regards to the impact of weather patterns. The change to colder water temperatures in the subtropical Pacific has been correlated to drier weather patterns for the central and western portions of the U.S. It is typical to have an El Nino move into a La Nina and this is likely going happen late this year and into early 2017 as a collection of model data suggests in graphic below. However, the models have changed in the past several weeks to a weaker La Nina with some models suggesting near neutral water temperature conditions.
Current sea surface conditions show a big change developing this summer as water temperatures are cooling off. The area of blue from west of South America along the equator westward shows the cooling trend as of July 14.
Current trends suggest that indeed a La Nina will be developing this fall and winter, however, it is becoming more and more apparent that it will not be a strong La Nina and possibly a La Nada (near normal water temperatures).
If indeed, we only have a weak La Nina or neutral conditions (La Nada), it will be good news as the potential for a severely dry 2017 is less in the western states. However, there is a lot of time between now and the fall season for things to change and will be monitoring water temperatures closely.