Discussion: The Climate Impact Company 2018 U.S. CDD forecast averaging 29 selected cities versus the NOAA 30-year normal indicates a steadily warming outlook. The forecast is nearly 10% warmer than original forecasts issued early last spring. The 2018 outlook is approaching the excessive warm MAY-SEP observations of 2016 and 2015 and recently passed last year’s very warm national average. One of the climate drivers is drier than normal regional soil moisture. This year much of the West and Central U.S. is in a dry-to-drought condition (Fig. 1) and the seasonal trend is drier (Fig. 2). The dryness is contributing early season record warmth adding to the 5-month CDD total.
Fig. 1: Daily U.S. soil moisture anomalies analysis.
Fig. 2: Seasonal U.S. soil moisture trend.