All natural phenomena have their time and for our current strong El Nino, time is up.
Observations have shown the beginning of a rapid weakening of El Nino, a decline predicted by models for quite a while. A decline so substantial that it will lead to a La Nina for next winter.
To tell this tale of decline, let’s start by looking at the key index of tropical Pacific sea surface temperatures, the Nino3.4 index, the difference from normal of sea surface temperatures in the central tropical Pacific (see map below).
The plot of Nino 3.4 temperatures over time (below), shows a warming that peaked during
November/December at around 2C above normal, with a cooling starting in January.
But like most things, the signs of real change are hidden beneath the surface. So let’s look at the warmth of water beneath the surface of the Pacific Ocean (see below).
Now we plainly see the future! The warmth of the water beneath the surface is rapidly declining. Over half the warmth is gone!
Consistent with such observations, the latest El Nino forecasts are predicting a rapid drop in the temperature in the Nino3.4 area, and thus a rapid attenuation of El Nino. By mid-spring, El Nino will be history. By next autumn, La Nino (colder than normal tropical water) will reign.
What are the implications of these changes?
For the next month, not much. The tropical waters will still be warm, with the typical impacts on atmospheric circulation. El Nino pushes the Northwest towards a warmer-than-normal situation, which is certainly what is predicted for the next week. California is normally wet under El Nino.
But El Nino is not destiny and the latest model forecast is for a very wet period over the West Coast from northern CA through BC for the next week (see forecast below). Good news for filling regional reservoirs.
I am getting increasingly optimistic about the Northwest regional water supply situation next summer.
