U.S. Drought: Weekly Report for December 19, 2023

According to the December 19, 2023 U.S. Drought Monitor, moderate to exceptional drought covers 27.9% of the United States including Puerto Rico, a decrease from last week’s 28.1%. The worst drought categories (extreme to exceptional drought) increased from 5.3% last week to 5.5%.

A strong ridge of high pressure dominated the upper-level atmospheric circulation across the contiguous U.S. during this U.S. Drought Monitor week (December 13–19). The ridge was responsible for warmer-than-normal temperatures across almost all of the contiguous U.S. and a dry week for much of the country. 

In opposition to the ridge, a strong low-pressure system developed over the Southwest and slowly moved east during the last half of the week. The low tapped Gulf of Mexico moisture to generate above-normal precipitation over the southern Rockies and southern to central Plains. The low and its frontal system dried out as it moved into the Midwest, but a new low formed over the Southeast. The new low-pressure system and its associated fronts tapped Gulf of Mexico and Atlantic moisture to spread above-normal precipitation across the Eastern Seaboard. As the week ended, a new Pacific weather system was poised to bring precipitation to the West Coast. 

Drought or abnormal dryness contracted or was reduced in intensity over parts of the Southwest, southern and central Plains, and East Coast, as well as the Pacific Northwest, where precipitation fell this week. Drought or abnormal dryness expanded or intensified in areas that have seen persistently dry conditions, especially in parts of the northern to central Rockies, eastern Texas, and central Mississippi to Ohio Valleys. 

Nationally, contraction was more than expansion, so the nationwide moderate to exceptional drought area decreased this week. Abnormal dryness and drought are currently affecting over 131 million people across the United States including Puerto Rico—about 42.3% of the population.