Tree in Autumn

November 2021 – Below Normal Temperatures and Precipitation Across Delaware

November Temperatures

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. 

November Precipitation

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).

National Anomalies

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).

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Wet droplets of rain on green leaves

November 2020 – Exceptionally Warm and Wet Across Delaware

November Temperatures

Preliminary data indicates that the statewide average temperature in November was 52.1o F, which is 4.5o F above the 1981-2010 mean value of 47.6o F (Figure 1).  November 2020 was the 2nd  warmest November since observations began in 1895.  Only November of 1985 has been warmer.

November Precipitation

Delaware’s statewide precipitation for November 2020 averaged 5.77 inches, 2.37 inches above the 1981-2010 mean (Figure 2).  This placed this month’s precipitation total as the 8th highest of all months since 1895

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were positive at all stations, with the largest anomalies found across Kent and New Castle Counties reaching to approximately 6o F at some stations (Figure 3).  Precipitation was above normal throughout the State, with departures of greater than four inches common across many areas (Figure 4). 

National Anomalies

Temperatures were above normal across nearly the entire United States, with the largest temperature anomalies (5o F – 10o F) found across the north-central portion of the country (Figure 5).  Precipitation anomalies varied greatly across the country with particularly heavy rainfall along the Atlantic coast from Florida to Delaware (Figure 6).  The 500 hPa height pattern for November shows a jet stream ridge covering the eastern two-thirds of the United States (Figure 7).  The placement of the jet stream north of its normal position is responsible for the warm temperatures seen across the country. 

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November 2019 – Cold and Dry Across Delaware

November Temperatures

Preliminary data indicates that the statewide average temperature in November was 43.6°F, which is 4.0°F below the 1981-2010 mean value of 47.6°F (Figure 1). This places November 2019 as the 22nd coldest since records began in 1895.

November Precipitation

Delaware’s statewide precipitation for November 2019 averaged only 1.46 inches, 1.94 inches below the 1981-2010 mean (Figure 2). This placed the November 2019 precipitation amount in the bottom one-third of months since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly below normal throughout the State (Figure 3), with the largest negative anomalies reaching values greater than -6°F. Precipitation was below normal at all stations across the State (Figure 4), with several stations in Kent County recording anomalies of greater than 2” below the long-term mean value.

National Anomalies

Temperatures were below normal throughout the eastern portion of the U.S, where some negative anomalies reached greater than 7°F (Figure 5). The western one-third of the U.S. saw above normal temperatures for the month, with parts of the Pacific Coast recording temperatures more than 5°F above normal. Precipitation varied greatly across the U.S. with very dry conditions across the Pacific Northwest and very wet conditions across the southwestern portion of the country (Figure 6). The 500 hPa height pattern for November showed a strong trough dominating the eastern U.S. (Figure 7), bringing the cold and dry conditions to our region.

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Icicles form on cast iron

November 2018: Record Precipitation and Cold Conditions Across Delaware

 

 

November Temperatures

Preliminary data indicates that the statewide average temperature in November was 46.2°F, which is 1.4°F below the 1981-2010 mean value of 47.6°F (Figure 1). Our cold November followed extreme warmth seen during September and October, making for an abrupt transition into the “winter” season for the First State.

November Precipitation

Delaware’s statewide precipitation for November 2018 averaged 7.28 inches, 3.88 inches above the 1981-2010 mean (Figure 2). November 2018 was the wettest since records began in 1895. Moreover, the year-to-date precipitation for the State, through the end of November, is also the highest year-to-date precipitation since 1895. An early season snowfall event brought early school closings and hazardous travel to Delaware on the 15th, when three inches of snow fell across the northern portions of the State.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were negative throughout the State (Figure 3), with the largest negative departures found across New Castle County. Heavy precipitation fell across the entire state, with the largest positive precipitation departures seen across northern Delaware, where some reached values of greater than six inches above normal (Figure 4).

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Berries grow from the branches of a plants

November Climate Conditions – Dry with Near Normal Temperatures Across Delaware

 
 

 

November Temperatures

Preliminary data indicates that the statewide average temperature in November was 47.5°F, which is the normal value for the month (Figure 1).

November Precipitation

Delaware’s statewide precipitation for November 2017 averaged 2.01 inches, 1.39 inches below the 1981-2010 mean (Figure 2), placing it in the driest one-third of Novembers since 1895.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures varied depending upon location across the State, with no departures exceeding 3°F (Figure 3). Precipitation departures were below normal at each station (Figure 4), with the driest conditions found across northern Delaware and Chester County, PA.

 

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Golden sky, dark clouds, and rain

Very Warm, and Moist Conditions Characterize the 2016 Autumn Season Across Delaware

 

 

Autumn Temperatures

Preliminary data indicates that temperatures were significantly above the 30-year normal during the autumn season. The statewide mean autumn temperature of 60.3°F was 2.7°F above the 1981-2010 mean value of 57.6°F (Figure 1). Autumn 2016 was tied with the 2005 season as the 2nd warmest autumn since records began in 1895.

Autumn Precipitation

The statewide mean precipitation of 13.23 inches was 2.40 inches above the 1981-2010 normal of 10.83 inches (Figure 2). However, much of the autumn total fell during September, when 9.43 inches of precipitation fell across the State, the 3rd wettest September total on record.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that autumn temperatures were much above normal across northern New Castle County and Chester County, PA, along with southern portions of Kent and northern Sussex counties (Figure 3).

Autumn precipitation varied appreciably across the State depending upon location. Very dry conditions were especially apparent across extreme northern Delaware and Chester County, PA (Figure 4), while southern Delaware saw much above normal precipitation during the autumn Season.

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Fall leaves in sunlight

November 2016: Very Dry & Warm Conditions

 

November Temperatures

Preliminary data indicates that the statewide average temperature in November was 48.7°F, 1.1°F above the 1981-2010 normal of 47.6°F (Figure 1). November was the fifth month in a row with temperatures appreciably above normal across the First State.

November Precipitation

Delaware’s statewide precipitation for November 2016 averaged 0.91 inches, 2.49 inches below the 1981-2010 mean of 3.40 inches (Figure 2). November 2016 was the 8th driest November since records began in 1895.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows that temperatures were well above normal across extreme northern Delaware and Chester County, PA during November (Figure 3). Temperatures were well above normal across inland Sussex County as well. Much below normal rainfall was the rule across southern Delaware, with smaller rainfall deficits found in northern Delaware and Chester County, PA (Figure 4).

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Drops of water on bright green grass

Temperature and Precipitation Both Above Normal Across Delaware During 2015

 
 
 

Annual Temperatures

Statewide mean annual temperature in 2015 was 56.4°F according to preliminary data from the National Climatic Data Center (NCDC). This was 1.0°F above the 1981-2010 normal of 55.4°F (Figure 1) and was the 11th warmest year in Delaware since 1895.

Monthly temperatures varied greatly throughout the year (Figure 2). The first three months of 2015 saw much below normal temperatures, including the 6th coldest February since 1895. The last nine months of the year saw above normal temperatures, except for October, which was slightly below normal. Tremendous warmth ended the year with December temperatures averaging 12.4°F above the 1981-2010 mean. December 2015 was the warmest December on record, smashing the old record by 6.1°F.

Annual Precipitation

Statewide precipitation in 2015 averaged 46.37 inches, 2.04 inches above the 1981-2010 mean of 44.33 inches (Figure 3).

Monthly precipitation anomalies varied between positive and negative throughout the year, with seven months of below normal and five months of above normal precipitation (Figure 4). June saw the largest precipitation anomaly of 5.30 inches above the 30-year normal, helping to push the annual value above the long-term mean.

Statewide Spatial Averages

According to data from the Delaware Environmental Observing System (DEOS; deos.udel.edu), mean annual temperature anomalies varied across Delaware (Figure 5). Northern New Castle County, much of Sussex County, southern Kent County and Chester County, PA all experienced above normal temperatures for the year. Coastal Sussex County and western portions of News Castle and Kent counties saw below normal mean annual temperatures.

Precipitation across the region varied substantially in 2015, ranging from just under 40 inches to greater than 50 inches at several locations across the State (Figure 6).

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Trees in Autumn

Autumn 2014 Slightly Dry with Near Normal Temperatures Across Delaware

Autumn Temperatures

de_statewideAutumnTemp-1895-2014_0.png
Figure 1. Delaware Statewide mean Autumn Temperature (°F) 1895-2014.

Preliminary data indicates that the statewide mean autumn temperature of 57.8°F was 0.2°F above the

1981-2010 normal of 57.6°F (Figure 1). The near normal autumn temperatures followed four consecutive seasons with below normal temperatures across Delaware. Temperatures

de_monthlyTempAnom_2014.png
Figure 2. Delaware statewide temperature anomalies for January 2014 through November 2014.

have been quite variable across the State during the year (Figure 2), with seven of the first eleven months being below normal.

Autumn Precipitation

Near normal autumn temperatures were accompanied by slightly dry conditions across the state during the autumn season. The statewide

de_statewideAutumnPrecip-1895-2014_0.png
Figure 3. Delaware Statewide mean Autumn Precipitation (°F) 1895-2014.

mean precipitation of 9.52 inches was 1.31 inches below the 1981-2010 normal of 10.83 inches (Figure 3). Monthly precipitation anomalies have varied between positive and negative during the year, but

no month has seen large departures from normal (Figure 4).

de_monthlyPrecipAnom_2014_0.png
Figure 4. Delaware statewide precipitation anomalies for January 2014 through November 2014.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperatures varied considerably across the State during the autumn season (Figure 5), with generally small positive or negative departures at most stations. The largest departures were found along the coastal areas of Sussex County where cool conditions were dominant.

Precipitation varied from as low as 7.51 inches along the Atlantic Coast to a high of 14.52 inches in western Chester County, PA. Even with this large variation, most stations in the region experienced slightly dry conditions during the season, with the greatest negative anomalies found along the Atlantic Coast and in northern Chester County, PA (Figure 6).

Autumn 2014 average temperature departures
Figure 5. Autumn 2014 average temperature departures from the 1981-2010 mean based upon DEOS station data.
Autumn 2014 precipitation departures
Figure 6. Autumn 2014 precipitation departures from the 1981-2010 mean based upon DEOS station data.
Bird on Tree

November 2015: Very Warm with Near Normal Precipitation Across Delaware

de_statewideNovTemp-1895-2015_0.png

Figure 1. Delaware statewide mean November temperature (°F) 1895-2015. Red line indicates 1981-2010 normal.
de_statewideNovPrecip-1895-2015_0.png

Figure 2. Delaware statewide November precipitation (inches) 1895-2015. Red line indicates 1981-2010 normal.

November Temperatures

Preliminary data indicates that the statewide average temperature in November was 51.5°F; this was 3.9°F above the 1981-2010 normal of 47.6°F (Figure 1), making November 2015 the fourth warmest on record since 1895. This November was the warmest since 2003.

November Precipitation

Delaware’s statewide precipitation for November 2015 averaged 3.24 inches, 0.16 inches below the 1981-2010 mean (Figure 2). November 2015 saw no snowfall accumulations anywhere in the State.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows that November temperatures were above normal across all of Delaware and Chester County, PA (Figure 3). Several stations in northern New Castle County, DE and Chester County, PA saw anomalies between 4° and 6°F above the 30-year normal for November.

Precipitation was below normal at the majority of locations across the State, with larger negative departures across the northern portion of the region (Figure 4).

November 2015 average temperature departures (°F) from the 1981-2010 mean based upon DEOS station data.

Figure 3. November 2015 average temperature departures (°F) from the 1981-2010 mean based upon DEOS station data.
November 2015 precipitation departures (inches) from the 1981-2010 mean based upon DEOS station data.

Figure 4. November 2015 precipitation departures (inches) from the 1981-2010 mean based upon DEOS station data.
 
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