Wet Soils To Suppress U.S. Summer Heat

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A very hot summer 2018 was foreshadowed by a widening dry-to-drought condition. This year widespread record wet soils are evident in the Central Plains, Midwest and East U.S. The soil moisture regime foreshadows a borderline anomalous hot summer ahead.

Selected Cities MAY-SEP 2019 % of 30-Year Normal CDD Forecast

Soil Moisture Ahead of Warm Season Suppresses Summer Heat

Discussion: The preliminary Climate Impact Company 2019 MAY-SEP percent of normal 30-year CDD forecast is (nationally) 102.8% of normal (Table 1). The value is considered marginally above normal. Last year a whopping 126.3% of normal was observed. One of the leading catalysts to the less warm forecast compared to last year is soil moisture. Note the increasing dry-to-drought zone across the U.S. last April to June (Fig. 1-2) compared to excessive wet soils as March 2019 ends (Fig. 3). Dry soils foreshadow anomalous hot summer heat ahead while wet soils suppress excessive heat potential.

Fig. 1-2: Last April and June dry soil moisture across the Southwest expanded and eventually contributed to an exceptionally hot summer nationally.

Fig. 3: Soil moisture ranking based on 1895-2019 climatology is at record wet levels in the Central and East U.S.

The warmest city forecasts for MAY-SEP 2019 include Seattle (124% of the 30-year normal) and Portland (113%) trailed by Boston and Burbank (each 108%). Seattle was the hot spot last warm season. The cool spots for MAY-SEP 2019 include Salt Lake City (74% of the 30-year normal) to Minneapolis (88%) plus Des Moines and Kansas City (each 96%).

%NormalMy-Se Vs. 30-yr%NormalMy-Se Vs. 30-yr
2019 Fcst2019 Class2018 Verif2018 Class
108%AboveBOS-Boston136%Much Above
109%AboveBDL-Hartford130%Much Above
105%AboveLGA-LaGuardia123%Much Above
105%AbovePHL-Philadelphia110%Much Above
105%AboveBWI-Baltimore119%Much Above
106%AboveDCA-Washington120%Much Above
106%AboveRIC-Richmond122%Much Above
104%AboveORF-Norfolk126%Much Above
103%NormalATL-Atlanta120%Much Above
102%NormalCMH-Columbus133%Much Above
104%AboveCLE-Cleveland149%Much Above
101%NormalCVG-Cincinnati138%Much Above
98%NormalORD-Chicago142%Much Above
96%BelowDSM-Des Moines131%Much Above
96%BelowMCI-Kansas City126%Much Above
105%AboveDFW-Dallas111%Much Above
104%AboveIAH-Houston110%Much Above
101%NormalDNR/DEN-Denver130%Much Above
74%Much BelowSLC-Salt Lake City120%Much Above
103%NormalLAS-Las Vegas117%Much Above
124%Much AboveSEA-Seattle178%Much Above
113%Much AbovePDX-Portland143%Much Above
103%NormalSAC-Sacramento97%Normal
108%AboveBUR-Burbank115%Much Above
102%NormalPHX-Phoenix105%Above
88%Much BelowMSP-Minneapolis139%Much Above
99%NormalDTW-Detroit133%Much Above
106%AboveFAT-Fresno113%Much Above
102.8%NormalNational126.3%Much Above

 Table 1: Climate Impact Company May to September forecast of percent of normal 30-year HDD by city and compared to 2018. 97 to 103 percent of normal is NORMAL; 103-109 percent (91-97 percent) is ABOVE (BELOW) normal. >109% is MUCH ABOVE normal. <91% is MUCH BELOW normal.