Matt Makens

As I write this update, I remain most interested in what happens to La Niña this
month. During January we saw a rapid warming of the sea surface temperatures,
especially in the 1.2 ENSO region and I anticipate further warming with another
MJO wave to move into that region this month. Let's begin with this topic before
turning to the month's outlook for precipitation and temperatures.

Here are the sea surface temperatures averaged from January 20th through
February 4th, 2023. Colder than normal water is shaded and blue. I've boxed the
ENSO regions 4, 3, and 1.2 (left to right).

Since our last update a couple weeks ago, the warming (weakening La Niña) is
most notable in the 1.2 region and eastern parts of 3.

I did not highlight the 3.4 region with a black box above, but it is the zone
between the two and I'll represent that part of the ocean in the following chart
showing a timeline of temperatures within the 4 regions.

You'll see that the trend in all regions is warming conditions since December.
La Niña, at least as indicated in the sea surface conditions, is weakening and
quickly so.

There will be further weakening in the next couple of weeks. Another wave
associated with the MJO (Madden-Julien Oscillation) will move from west to east,
and the wind associated with that will continue to support warming ocean water
and upwelling of warmer water at depths. 

I see no reason to dispute the forecast probabilities representing a neutral sea
surface pattern by March. The model breakout is shown below via B.O.M.

All major forecast centers point to a neutral 3.4 ENSO region. Let's, however,
look at the atmosphere which may not fade from La Niña as quickly.

Using the SOI (Southern Oscillation Index) as a guide, the atmosphere (this
index uses sea level pressure as a measure of the atmosphere's ENSO pattern) was
strongly La Niña in December and for much of January but has weakened to close
out the month and begin February. It IS still La Niña, however. I have written
in a number of previous updates that the fate of La Niña in the oceans is one
thing, and another entirely for the atmosphere. The atmosphere will take time to
adjust and, frankly, may jump between La Niña and El Niño values for the next
several months - probably chaotically so. 

For a future discussion, I'm not totally discounting a Modoki La Niña for the
rest of 2023. In a quick nutshell: Modoki events are like sandwhiches, the ENSO
4 and 1.2 region are the opposite of the 3 region. In this case, region 3
remains cold and in La Niña and the 4 and 1.2 regions are warm. A Modoki El Niño
is when region 3 is warm and the other two are cold. If that does pan out, those
hoping for a robust El Niño will be disappointed. However, a Modoki La Niña will
still support a wetter picture for the U.S. particularly east of the Rockies
versus a traditional La Niña. Of the two, a Modoki is more favorable for
precipitation. Again, I don't want to get too involved in that discussion....
yet.

Okay, with the status of La Niña ocean impacts decreasing, yet still
atmospherically viable, let's turn to the outlook for February's precipitation
and temperature patterns.

A quick look at the analog forecast I create the month gives us:

Those are relatively close to what the CPC has projected for February.

The biggest difference I see is in the temperature projections. The cold
weather, as reflected in my analog forecast, relied upon a strong ridge over
Alaska and stronger Polar Vortex activity which drives colder temperatures down
from Canada for those east of the Rockies. There's still another chance that
occurs later in February, but it is too uncertain to plan on at this point.
Barring that cooling, yes the CPC forecast is on track. Since my forecast was
produced January 20th, and CPC's the 31st, we are about a week's worth of
difference in data, and I'd think an average of the two is probably the best as
I see things today. So, bring the CPC's cold east and north a touch and my cold
south and west a bit. 

As far as the precipitation outlooks, both are very similar, and both appear on
track thus far. My analog years did suggest a push of late-month moisture for
the Western U.S. and that still remains on track in modeling. The last week of
February will be the wettest for the Cascades to Sierras and coastal areas from
California to Washington. In the end, those regions may end the month wetter
than normal if that moisture pans out, but my analogs and the CPC both had equal
chances there so that'll verify us both.

In terms of drought. There will be some improvement, albeit limited this month.
It's hard to argue much with the drought outlook shown here:

There's improvement coming to the Osage and Flint Hills country of Kansas and
Oklahoma in that drought outlook, and those would be areas I'll be curious to
see pan out. Yes, both moisture outlooks for the month have that area close to a
surplus but it is pretty darn close and the beneficial moisture may stay east of
there. For Northern California, any drought removal will need to come with that
late month moisture - remember they are way behind still. 

I'll leave you with a quick look at soil moisture (surface) to show we need a
lot of help on the Plains toward the Midwest. Recent moisture - the ice storm -
in Texas helped out a bit there, the snows for Nebraska and South Dakota helped
some (remember that soil is frozen so it isn't going to be absorbing much
water). 

As we hit the growing season very shortly, we will need moisture on those
Plains!

La Niña rapidly weakens, what that means for our weather as we move through February and into spring