Drought Has Expanded Rapidly Across the Southern U.S. Since Fall and the Outlook Into Spring Is Worrisome

Linda Lam
Published: January 13, 2018

Drier-than-average conditions have impacted much of the South since early fall, resulting in a rapidly expanding drought across the region. Unfortunately, this trend in below-average precipitation is expected to continue into early spring.

The latest data released by the U.S. Drought Monitor this week showed that almost 58 percent of the contiguous U.S. is seeing at least abnormally dry conditions.

In addition, just over 32 percent of the Lower 48 is experiencing drought conditions. This is the highest percentage in drought since October 2015.

Abnormally dry and drought conditions on January 9, 2018. Red areas indicate areas experiencing worse drought.
(U.S. Drought Monitor)

This drier weather pattern across the South is consistent with what is expected during a La Niña winter. There is also new research that suggests that more widespread drought may occur during a second consecutive winter of La Niña conditions.

(MORE: What La Niña Conditions Mean for Winter in the U.S.)

The latest update from NOAA indicates that La Niña conditions are expected to persist through winter. La Niña is the periodic cooling of the equatorial eastern and central Pacific Ocean by at least 0.5 degrees Celsius, along with consistent atmospheric indications. 

According to the U.S. Drought Monitor, "over the last 60 days, extensive areas of the country have recorded below 25 percent of normal precipitation, from the Southwest into the central Plains and Midwest as well as in the Southeast and into the Mid-Atlantic." In addition, as of Jan. 9, "some areas of the Oklahoma and Texas panhandles and southern Kansas have gone 95-100 straight days with less than 0.10 inches of precipitation, with several locations reporting no precipitation at all during that time."

(MORE: Winter Misery Index)

As a result of the lack of precipitation, drought conditions have quickly expanded across the southern tier of the U.S. since September.

Image on the left shows the lack of drought conditions in the South in early September, while the image on the right shows where drought conditions have developed in early January.
(U.S. Drought Monitor)

On Sept. 5, 2017, there was no drought observed in the Southeast. However, as of Jan. 9, just over 37 percent of the region is now in at least moderate drought. In addition, almost 77 percent of the region is currently abnormally dry compared to just over 8 percent in early September.

In the South, which includes Tennessee and Mississippi westward into Texas, only 0.45 percent of the region was seeing drought conditions on Sept. 5, and that percentage has jumped to 45 percent as of Jan. 9. The percentage of the area that is at least abnormally dry has also dramatically increased from just under 3 percent in early September to almost 74 percent in early January.

(MORE: 2017 Was Third-Warmest Year on Record for U.S., NOAA Says)

Amarillo, Texas, is an example of one of the areas that has seen very little rainfall, with only a trace recorded since Nov. 1. The average rainfall during this period should be around 1.75 inches.

Is There Any Relief Ahead?

The drought comparison map above also shows the drought improvement that has occurred in the northern Plains. This is also typically what is expected in a La Niña winter.

Typically, the jet stream during a La Niña winter steers the storm track farther north, leading to drier conditions for much of the southern tier of the U.S., with the wetter conditions farther north. 

General weather pattern in a La Niña winter.

However, the weather pattern that has been in place has brought colder-than-average temperatures so far this winter to much of the southern and eastern U.S., with temperature the greatest above average in the Southwest. The warmer temperatures in the Southwest have been due to a persistent ridge of high pressure, which has also resulted in the dry conditions observed there.

(MAPS: Weekly Planner)

Given the expectation that La Niña conditions will last through the winter and will then transition to neutral conditions, neither La Niña or El Niño, this spring, there are concerns that drought conditions will worsen.

Areas in darker green have the greater chance of above-average precipitation, while locations in darker brown have a greater chance of below-average precipitation.

The precipitation outlook from NOAA indicates that generally drier-than-average conditions are expected through March from the Southwest into the southern Plains and much of the South. The highest chance for drier-than-average conditions is across Florida and from southwestern South Carolina into southeastern Louisiana.

This would not be good news and would likely lead to an expansion in areal coverage and worsening of already existing drought conditions from California to the Southeast.

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