Southeastern Drought Overview
Although the Southeast often receives excessive precipitation, it is no stranger to drought. Drought conditions can develop rapidly across the region from lack of tropical cyclone activity, warm season rainfall variability, increased evapotranspiration rates, and increased water usage (Kunkel et al. 2013). The position of the Bermuda High strongly influences summer precipitation; when it's located in the northwest quadrant of the Southeast, the region is susceptible to drought conditions (Li et al. 2012).
The El Niño-Southern Oscillation (ENSO) can influence precipitation patterns across the Southeast. ENSO has two phases that are determined by sea surface temperature (SST) deviations across the equatorial Pacific Ocean. If the SSTs are above normal, ENSO is an El Niño or warm phase. If the SSTs are below normal, ENSO is a La Niña or cool phase.
Both phases impact the Southeast quite differently. An El Niño enhances the subtropical jet stream, causing above average precipitation across the southern states (Higgins et al. 2002). El Niño also reduces the probability of winter temperature extremes across the South (Higgins et al. 2002). In contrast, La Niña is associated with negative precipitation anomalies and increased risk of drought across the region (Mo et al. 2009). La Niña can also cause warmer than normal temperature conditions over most of the region (Higgins et al. 2002).
Follow the link for a two-page (pdf) synopsis of Drought Impacts on Forests and Rangeland in the Southern Region.
Higgins, R.W., A. Leetmaa, and V. E. Kousky. "Relationships between climate variability and winter temperature extremes in the United States."Journal of Climate 15.13 (2002): 1555-1572.
Kunkel, K.E, L.E. Stevens, S.E. Stevens, L. Sun, E. Janssen, D. Wuebbles, C.E. Konrad II, C.M. Fuhrman, B.D. Keim, M.C. Kruk, A. Billet, H. Needham, M. Schafer, and J.G. Dobson, (2013). Regional Climate Trends and Scenarios for the U.S. National Climate Assessment. Part 2. Climate of the Southeast U.S. NOAA Technical Report NESDIS 142-2, 95 pp.
Li, W., Li, L., Ting, M., & Liu, Y. (2012). Intensification of Northern Hemisphere subtropical highs in a warming climate. Nature Geoscience, 5(11), 830-834.
Mo, Kingtse C., Jae-Kyung E. Schemm, and Soo-Hyun Yoo. (2009). "Influence of ENSO and the Atlantic multidecadal oscillation on drought over the United States." Journal of Climate 22.22: 5962-5982.
Current Drought Conditions
The U.S. Drought Monitor is a partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration. The Drought Monitor summary map identifies general drought areas and labels drought conditions by intensity, with D1 being the least intense and D4 being the most intense. D0, drought watch areas, are either drying out and possibly heading for drought or recovering from drought but not yet back to normal, suffering long-term impacts such as low reservoir levels.