Brian Bledsoe

We will continue to update you on the progress of La Niña, because we think it
is the single most important thing in our long range forecast. Granted, we still
have a ways to go before the active hurricane season comes to an end, but the
development of La Niña will likely have some pretty big ramifications.

At the time of this article, here is a look at the sea surface temperature
anomalies: 

cYou can see the “blue and green” shading off the west coast of South America,
indicating cooler than average sea surface temperatures. This has been
persisting for awhile, and as we've been talking about for months, the likely
development of a La Niña. The above map looks a lot like it did at the same time
in 2013...see below.

As of right now, the Pacific isn’t as cold as it was the last time we had a
stronger event. You can see from the Pacific Decadal Oscillation chart below,
that the PDO was considerably more negative (colder Pacific Ocean) than what we
have now: 


While the PDO is a bit more negative (colder) now than in 2017, it isn’t as
negative or as cold as it was between late 2010 through 2013. When the PDO is
more negative/colder, La Niña episodes tend to be stronger and more long lived.
So while any type of La Niña isn’t necessarily good news, we may have an event
that doesn’t cause as long of a drought as we’ve had with past events. This of
course is not a guarantee, but instead a possibility and something we'll watch
for. 

Some of the latest modeling takes this La Niña event to moderate strength this
winter. The colored lines in the chart below indicate various models and their
forecasts. The more the line dips below zero, the stronger the model thinks the
La Niña will be. As you can see, some models have no La Niña episode at all.
However, given the current state of the water along the equator in the Pacific,
La Niña appears poised to develop further.

I wanted to look back to see how the end of 2013 and beginning of 2014 looked.
The maps below show precipitation anomalies from September 2013 to March 2014.


In 2013, we were also struggling with drought. Here is the Drought Monitor from
early September 2013.

After the early September flood, much of the drought on the Northern Front Range
was eliminated. For most of the state, the drought continued to improve during
the winter. In fact, by late March most of the state was much improved.

However, the areas that are usually hardest hit by La Niña (the Southeast
Plains), continued to struggle with the drought. So, while La Niña isn't always
bad for everyone in the state, it can still create and maintain drought for some
areas. This isn't a good thing, because almost all of the state is dealing with
drought right now.

La Niña update and potential analog year as we look ahead to fall