Heavy to record-setting rainfall soaked much of the western half of the nation, providing substantial drought relief but triggering historic flooding. The most dramatic meteorological event unfolded prior to mid-month in Colorado, when the interaction between the monsoon circulation and a cold front led to unprecedented rainfall and deadly flooding. During the week-long deluge, rainfall totaled 6-18 inches or more at several locations along the eastern slopes of the central Rockies.
Later, precipitation intensified across the Northwest, leading to record-setting September rainfall totals west of the Cascades. Throughout the West-excluding parts of central and southern California and adjacent areas in the Great Basin-rainfall aided drought-stressed rangeland and pastures.
In contrast, a broad area across the eastern half of the United States received only light rain. In parts of the Midwest, monthly temperatures averaged more than 5°F above normal, while rainfall totaled less than half of normal.
Unusually dry weather also prevailed in the Atlantic Coast states, excluding Florida's peninsula and New England. In addition to those two regions, exceptions to the dry pattern included portions of the Dakotas and the western and central Gulf Coast states.
Weatherwise Contributing Editor BRAD RIPPEY is the U.S. Editor of the Weekly Weather and Crop Bulletin of the Joint Agriculture NOAA Weather Facility.
Weatherwise Contributing Editor JEFFREY B. HALVERSON is an associate professor of geography at the University of Maryland, Baltimore County.