Expanding U.S. Drought. Worst Since 1956 by End of December.

Discussion: The latest U.S. Seasonal Drought Outlook by NOAA indicates eastward expansion of the West/Central U.S. drought (Fig. 1). NOAA indicates drought development in the Mid-south U.S. and the entire northwest/north Gulf of Mexico region. Drought expansion in parts of the East-central U.S. is also affected. The end-of-year dry signature is likely the strongest since 1956 (Fig. 2) which was also the 3^rd year of a 3-year La Nina pattern. Enhancing dry risk nowadays is the warming of the middle latitude oceans which encourage stronger than normal high-pressure which encourage drought patterns (Fig. 3). The current U.S. soil moisture anomalies identify the Great Plains to Texas as having the most significant dry soils (Fig. 4). The September climate re-enforced this dry signature as minimal rainfall caused widespread sharp decline in soil moisture centered on the Mid-south and western Gulf States (Fig. 5). While warm SSTA encourages high pressure and drought regimes, if a tropical cyclone moves across warm SSTA regions, historic rains occur due to the increased available moisture in the lower atmosphere caused by warm SSTA. Ian was an example of this type of storm. The Climate Impact Company 5-month precipitation anomaly forecast indicates the Mid-south (and Southeast) U.S. dry climate persists through meteorological winter (Fig. 6).

Fig. 1: NOAA/CPC U.S. Seasonal Drought Outlook valid through Dec. 31, 2022.

Fig. 2: The end of 1956 U.S. Palmer Drought Severity Index analysis reveals the intense drought of a 3^rd year of La Nina.

Fig. 3: La Nina combined with warm SSTA patterns in the middle latitudes have contributed to harsh drought in the U.S. (plus China and Europe) in 2022.

Fig. 4-5: Current U.S. soil moisture anomalies and 30-day change analysis from NOAA.

Fig. 6: CIC-CA forecast of precipitation anomalies valid October 2022 through February 2023.