Climate and Weather

Is La Niña's Thumbprint This Winter a Growing Southern U.S. Drought?

At a Glance

Drought has grown across large portion of the southern U.S. since fall.
La Niña typically leads to dry winters across the nation's southern tier.

Drought conditions have exploded in coverage across the nation's southern tier this winter and La Niña could be at least partially to blame.

La Niña is a periodic cooling of the eastern and central equatorial Pacific Ocean waters, which can influence weather patterns globally. This effect is most prevalent in the winter months for the Northern Hemisphere where the United States is located.

The tendency for dry conditions in the southern tier of states is a typical expectation during a La Niña winter based on climatological history. As of early January, this winter's La Niña was close to meeting the criteria for a moderate event, according to NOAA's Climate Prediction Center.

Abnormally dry or drought conditions have undergone a large expansion since fall from Southern California to the Southern Plains and Southeast, falling in line with the dry southern United States expectation during La Niña. You can see this in the growing yellow, orange and red contours across the nation's southern tier in the U.S. Drought Monitor animation below.

Abnormally dry (dry) or drought conditions (moderate, severe, extreme, exceptional) have spread across a large portion of the nation's southern tier since the start of October. (Data: NOAA/NDMC/USDA)

In the Southeast region of the U.S. Drought Monitor, the coverage of moderate or worse drought conditions has grown from 0 percent to near 46 percent from early October to late January. This region encompasses Alabama, Florida, Georgia, South Carolina, North Carolina and Virginia.

It's a similar story in the South region, which is made up of Arkansas, Louisiana, Mississippi, Oklahoma, Tennessee and Texas. Drought conditions across those states have jumped in coverage from 6 percent to 54 percent in the same period of time.

Arizona, Colorado, New Mexico and Utah have seen the largest drought expansion in the western region. The entire state of Arizona, for example, is being affected by at least some level of drought as of late January. That is up from just 11 percent in early October.

On a city level, Amarillo, Texas, had not seen measurable rain (0.01 inches or greater) in 107 days as of Jan. 28. This crushes the Texas Panhandle city's previous record dry streak of 75 days set in 1957.

The past 90 days ending Jan. 28, rank as the driest on record in Albuquerque, New Mexico, fourth driest in Birmingham, Alabama, and eighth driest in Tallahassee, Florida, according to data from the Southeast Regional Climate Center.

Since Oct. 6, Albuquerque has seen just one day with measurable precipitation, a measly 0.03 inches of rain on Jan. 10.

Second Year La Niña Causes Worse Drought?

This is second La Niña winter in a row, but the United States emerged from the weak event of a year ago in much better shape when comes to drought conditions in spring. In fact, the coverage of drought in the United States last April dropped to its lowest level since the Drought Monitor was first produced in 2000.

Percent of Average Precipitation the Past 90 Days
In general, the southern half of the U.S. has seen below-average precipitation in the 90 days ending Jan. 28. Parts of the Midwest and mid-Atlantic are also seeing drier-than-average conditions the past 90 days. (NOAA/Climate Prediction Center)

The larger drought coverage in the United States so far this winter compared to last year appears to fall in line with the findings of a study published in October in Geophysical Research Letters.

Although the sample size of research years is small, it found that the drought coverage in the second year of a multi-year La Niña crept farther north and east across the Lower 48, as meteorologist Bob Henson detailed in a late-December wunderground.com Category 6 blog entry.

This includes a swath from the Southwest to the Southern Plains, Midwest and Southeast, Henson added. Those are many of the same locations being affected by a growing drought this winter.

As always, the existence of La Niña or it's counterpart El Niño is just one factor. Other overriding factors in the atmosphere can lead to different outcomes when it comes to precipitation or temperature expectations.