Brian Bledsoe

We are midway through the winter, and with that it's time drop you a note about
what La Niña is up to. 

First, a look at SST (sea surface temperature) anomalies across the equatorial
Pacific:

The above animation runs from early November through late January. Notice the
blue shading really shrinking across the central and eastern Pacific Ocean. This
is occurring at the surface of the ocean, and shows those anomalies not only
becoming smaller, but also of less magnitude.

The animation below shows what is occurring beneath the surface and from west to
east across the Pacific. 

Notice the blue area not only shrinking, but becoming more and more shallow.
While this is happening, warmer than average water (orange/red shading) is not
only developing, but spreading farther east. Both of these things indicate to me
that this episode has not only peaked, but is rapidly going away. Does that mean
it will end completely sooner than forecast?Not necessarily, but a change this
big certainly can't hurt.

As of right now, the models do not show a major shift toward an El Niño event.
However, history suggests that after we have a double dip La Niña episode (two
years in a row), we will usually see some sort of an El Niño develop toward the
latter half of the second year. 

The graphic below shows the trend from La Niña to neutral, and then warming
toward a potential El Niño event. The lines are pretty close together and this
indicates most of the model members have a similar handle on things. That's
good, because the farther you go out in time, the farther apart those lines
usually get. 

Given the above, some might ask why models are not wetter in the coming months,
given the fact that this La Niña event has peaked and will continue to weaken.
That quick transition to wetter conditions isn't always the case, plus we won't
be completely done with La Niña for a while longer. We also have a very
negative/cold Pacific Decadal Oscillation to overcome. 

You can see in the above graphic how negative/cold the PDO has been for the past
year. Recently, readings for the past three months have been some of the most
negative/cold since the mid 1950s! Usually, that accounts for a fair amount of
drought development and drought maintenance for our region. You can see that in
the drought monitor graphics below:

The latest NMME model precipitation forecast for March,April, May shows a rather
ominous scenario for many areas that are already dry. 


Notice the stout dry signal through the Southern Rockies, Texas and the Western
High Plains. This doesn't relax a lot for May,June, July... The dry signal also
starts to migrate northward, which can often be a signal of a transition to El
Niño.


So, while La Niña is on its way out, I am not convinced yet that we will
immediately see better conditions for areas still struggling with drought. Is
the recent moisture and increasing storm frequency a good thing? Absolutely!
However, the PDO remains quite negative and that usually favors a drier than
average forecast for most of our region. Will there be storms? Of course...but,
the storms actually have to produce for us. Otherwise, we just get a bunch of
wind and we are right back to talking about drought and fire danger.

Finally, this is also the time of year that is referred to as "the spring
predictability barrier" when it comes to long range forecasting. A lot of the
longer range models struggle a bit until we get into May. Hopefully, we can see
some of the "trend changes" start to show up in the modeling in the next several
weeks and have a bit more to go on.

February, 2022 La Niña update and what that may mean for precipitation patterns as we head toward spring and summer