December 2019 – Warm and Moist Across Delaware

December Temperatures

Preliminary data indicates that the statewide average temperature in December was 40.2°F, which is 2.1°F above the 1981-2010 mean value of 38.1°F (Figure 1). This places December 2019 as the 23rd warmest since records began in 1895.

December Precipitation

Delaware’s statewide precipitation for December 2019 averaged 4.26 inches, 0.69 inches above the 1981-2010 mean (Figure 2). This placed the December 2019 precipitation amount in the top one-third of months since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly above normal throughout the State (Figure 3), with most anomalies ranging from 1° to 2° F. Precipitation was above normal at all stations across the State (Figure 4), except for the extreme southeast. The largest positive precipitation departures were found across northern New Castle County.

National Anomalies

Temperatures were above normal throughout the majority of the U.S, with some departures reaching 7° to 10° F in the Midwest (Figure 5). Precipitation varied greatly across the U.S. with very wet conditions across the northcentral States and much of the eastern one-third of the country (Figure 6). The 500 hPa height pattern for December showed a ridge dominating the northeastern two-thirds of the U.S. (Figure 7), bringing generally warm and moist conditions to our region.

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