Brian Bledsoe

In recent weeks, we have seen some changes take place with the ongoing La Niña
episode, primarily in that it has weakened by quite a bit. The series of
graphics below shows that trend.

Sea Surface Temperature Anomaly Change 

Sub Sea Surface Temperature Anomaly Change

Two very noticeable things are occurring. 1) the pronounced cold pool at the
surface has warmed and almost disappeared and 2) the colder than average water
that existed down to about 150 meters in the Central/Western Pacific has started
to erode. It is not only eroding, but is being replaced by warmer than average
water that is migrating eastward. 

Those two changes alone signifies to me, that this event is basically done. But
let's look at a few other things before we completely sign off on that thought.

Equatorial Upper Oceanic Heat Anomalies

You can see that we've been dealing with cooler than average equatorial ocean
temperatures since last spring. Only recently have we started to return to
average, and in some cases, a little above average.

IRI/CPC Model ENSO Predictions
In the image below you can see that the majority of the models in the above
graphic show us returning to "neutral" ENSO conditions in the next couple
months. However, most of them do keep us a little cooler than average through
the rest of the year. 

We are officially in the "spring unpredictability barrier", which means that the
models struggle to resolve certain things during the spring. However, given the
current situation from what I have shown above, I wouldn't anticipate a rapid
return to moderate or strong La Niña conditions. 

So, what does that mean for us in terms of temperature and precipitation for the
rest of the spring and summer? Here is what the updated IRI Multi-Model
Probability is showing.

April - June Temperature Forecast

April - June Precipitation Forecast

June - August Temperature Forecast

June - August Precipitation Forecast

You can see that there is a substantial tip in the probability toward a warmer
than average rest of spring and summer. This is especially true for the western
half of the country. There is also a tip toward drier than average conditions
for parts of The Plains and much of the Western United States.

While recent drought relief has been a huge help for parts of The Plains and
Rockies, areas farther west and southwest have not been as lucky. Because of
that, the regional drought footprint still exists and can always expand. That is
something we'll be watching for in the next couple of months.

What a weakening La Niña could mean for spring and summer temperature and precipitation patterns across the Plains