El Niño shifting to a La Niña?

The El Niño is moderating according to the NOAA. This weather is usually followed by a La Niña, but not always. So what does this mean for our weather? In the US the El Niño usually results in a warmer than normal winter for part of the country and above normal precipitation for the southern portion of the country. The El Niño of 2015-2016 is one of the strongest on record according to the NOAA, "having large consequences on global weather......The El Niño of 2015-2016 is already one of the strongest on record, having large consequences on global weather."

Basically with an El Niño the sea surface temperature across the equatorial Eastern Central Pacific Ocean is warmer than normal. As this temperature falls the El Niño is said to moderate. When the temperature of that area of the ocean is cooler than normal it is said to be a La Niña,

Currently the ocean temperature is falling and the NOAA currently predicts that the El Niño conditions are likely to transition to neutral conditions (neither El Niño nor La Niña) during late spring and early summer 2016. "The chance of La Niña conditions will increase to about 65-70% by autumn. Once in place, a La Niña event can last for two years or even longer."

What does this mean for our weather? Long range forecasting is very difficult. However, the April 21 temperature map at the top of this post is the NOAA's best guess at the probability for temperatures for the period of May, June and July 2016. The NOAA gives a 33% probability that temperatures will be above normal in northern Illinois. The map is only a probability. It does not necessarily mean that there will be higher or lower temperatures than normal.

For more about reading the map, Click for NOAA Map Explanation

What about rain? This is the probability map from the NOAA for the same three month period. The white indicates equal probabilities for more rain, a normal amount or less rain for northern Illinois:

During La Niña weather, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3 to 5 °C. In the US a La Niña is declared if these lowered temperature conditions occur for at least five months.  To make things confusing, there are different types of  La Niña, determined by temperatures in the eastern pacific and central pacific ocean.

A La Niña does not always follow an El Niño.

If we do get a La Niña we'll see generally the opposite effects of El Niño. During a La Niña there may be more (above average) precipitation in the northern Midwest, the northern Rockies, Northern California, and portion of the Pacific Northwest. Precipitation in the southwestern and southeastern states will likely be less (below average).  The La Niña may provide conditions for stronger than average hurricanes in the Atlantic.