According to the August 15, 2017, U.S. Drought Monitor, moderate to exceptional drought covers 11.3% of the contiguous United States, a slight increase from last week’s 11.2%. The worst drought categories (extreme to exceptional drought) also increased slightly from 2.4% last week to 2.5%.
For most of this U.S. Drought Monitor week, an upper-level ridge of high pressure dominated the western contiguous United States, an upper-level trough held sway over the eastern Lower 48, and the Bermuda High controlled the weather over much of the North Atlantic. This circulation pattern helped to deflect tropical cyclones away from the contiguous United States, steering Hurricane Franklin across Mexico and keeping Hurricane Gert out to sea over the Atlantic.
The ridge/trough pattern over the Lower 48 shifted to the east near the end of the week. But for most of the week, cold fronts guided by the upper-level trough brought below-normal temperatures to most of the contiguous United States, especially from the Plains to Midwest. The fronts and low pressure systems triggered showers and thunderstorms which brought above-normal precipitation to parts of the central Rockies, Great Plains, and Southeast. Precipitation was below normal across much of the West, Midwest, and Northeast.