Preliminary data indicates that the statewide average temperature in November was 45.6°F, which is 1.9°F below the 1991-2020 mean value of 47.5°F (Figure 1). November’s average temperature was the first month with below normal temperatures since February of 2021.
Delaware’s statewide precipitation for November 2021 averaged 1.02 inches, 2.25 inches below the 1991-2020 mean (Figure 2). This placed this month’s precipitation as the 13th lowest November precipitation since records began in 1895.
Statewide Spatial Anomalies
Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly below normal across the entire State, with many stations seeing negative temperature anomalies of between 2°F and 3°F (Figure 3). Precipitation was below normal across the entire state with some stations reaching negative anomalies of greater than 4 inches (Figure 4).
Temperatures were below normal across most of the eastern one-third of the United States, with the largest negative temperature anomalies found across the Ohio River Basin. The western two-thirds of the United States saw significantly above normal temperatures, with some anomalies reaching as much as 7°F to 10°F above normal across the Rocky Mountain states (Figure 5). Precipitation anomalies varied greatly across the country (Figure 6), with excessively dry conditions across much of the country except for Florida and the state of Washington. The 500 hPa height pattern for November shows a strong jet stream trough located over eastern North America and a strong jet stream ridge over western North America contributing to the temperature extremes across those regions (Figure 7).