Chesapeake Bay Climate Impacts Summary and Outlook
Mid-Atlantic Regional Climate Impacts Summary and Outlook: Spring 2020
- Temperatures varied widely across the spring months, with sites across the Chesapeake Bay watershed experiencing one of the warmest months of March on record, followed by one of the coldest months of April on record.
- Washington, D.C.; Baltimore, Maryland; and Washington Dulles International Airport in Virginia all tied their records for least snowy spring.
- This spring, the southeastern portion of the Mid-Atlantic region experienced drier conditions than normal, while the northwestern portion of the region experienced up to 150 percent of normal precipitation.
- The Atlantic Hurricane Outlook suggests an above-average Atlantic hurricane season.
- Analysis of historic spring temperatures shows that dates of last freeze and the onset of warm temperatures have shifted earlier in the year over the past four decades.
- Future projections show that the region as a whole may experience the onset of warm spring temperatures 15–26 days earlier than normal by the end of the century, and the last day of frost 12–20 days earlier.
Part 1: Significant Weather Events and Impacts
March 2020 ranked among the five warmest Marches on record for several sites in the Chesapeake Bay watershed including Baltimore, Maryland; Washington, D.C.; and Lynchburg, Norfolk, and Richmond, Virginia.1 March 20 and 29 were particularly warm in the southern portion of the watershed, with high temperatures reaching well over 80 °F in the warmest locations. Both days ranked among the ten hottest March days on record for Norfolk, Virginia, and March 29 was the fourth-hottest March day on record in Lynchburg, Virginia.2
In contrast with March, this April was the eighth-coldest on record for Binghamton, New York, and the fifteenth coldest April for the Washington Dulles International Airport in Virginia.3 In fact, Binghamton, New York, recorded its coldest highest maximum temperature for the month of April.4 Similarly, the highest temperature reached during April at Dulles International Airport was 78°F, the second-coldest highest maximum temperature for April on record.5 This marks only the fourth time on record that Dulles International Airport failed to reach 80°F in the month of April. Additionally, the highest maximum temperatures in Scranton, Harrisburg, and Williamsport, Pennsylvania, all ranked among their five coldest on record. Scranton and Williamsport also saw fewer days than usual in April with a high of at least 70°F (recording one day and two days, respectively)—making this April one of those with the fewest days that reached 70°F on record. 6
The colder-than-normal trend continued into May. On May 8–10, as the polar vortex weakened and Arctic air moved into the region, high and low temperatures were as much as 30°F colder than normal.7 The coldest low temperatures ranged from the teens to the 30s.8 During this period, Binghamton, New York; Harrisburg, Pennsylvania; and Lynchburg, Virginia, each had their coldest May temperature on record.9 The low temperatures ranked as the second-coldest for May in Richmond, Virginia; as the fourth-coldest in Scranton and Williamsport, Pennsylvania, and among the ten coldest for May in Baltimore and Salisbury, Maryland.10 On May 9, high temperatures struggled to reach 50°F. Binghamton, New York had its coldest maximum temperature for May on record, while Harrisburg, Pennsylvania, and Dulles International Airport had their second-coldest for May.11 The maximum temperatures in Williamsport and Scranton, Pennsylvania, ranked among the six coldest on record for May.12
Just a few weeks later, the watershed experienced unusually mild temperatures from May 26–29. On May 26, high temperatures in the northern portions of the watershed were up to 20°F above normal, with the warmest locations reaching the upper 80s to low 90s.13 Scranton, Pennsylvania, tied its hottest May day on record at 93°F, while Binghamton, New York tied its third-hottest May day with a high of 88°F.14 Low temperatures on May 28–29 ranked among the five warmest on record for May in Richmond, Lynchburg, and Dulles International Airport, Virginia; and among the ten warmest on record for May in Baltimore, Maryland; and Williamsport, Pennsylvania.15 Despite the warm-up at the end of the month, this May still ranked among the twenty coldest on record for Richmond and Dulles International Airport, Virginia.16
A graphical representation of the temperature variability seen this spring at Dulles International Airport is shown in Figure 2, which appears and is discussed in more detail in Part 2.
Martinsburg, West Virginia, recorded 18 days with measurable precipitation (at least 0.01 inches) in March, setting its record for the greatest number of March days with precipitation.17 Dulles International Airport recorded its greatest number of April days with measurable precipitation, with 16 days. Washington, D.C.; Baltimore, Maryland; and Binghamton, New York, all recorded numbers of April days with measurable precipitation that ranked among the top five on record for their sites.18
This April ranked among the ten wettest on record for Washington, D.C.; Harrisburg, Pennsylvania; Dulles International Airport; and Lynchburg, Virginia. It was also among the twenty wettest Aprils for Williamsport, Pennsylvania; Baltimore and Hagerstown, Maryland; Richmond, Virginia; and Binghamton, New York.19
From May 18–22, a stalled storm system produced heavy rain and flooding in southwestern Virginia. Parts of Botetourt County received 6–8 inches of rain in this period and had several roads close due to flooding.20 Water levels on Craig Creek at Parr and Catawba Creek, near Catawba, both in Botetourt County, were among the ten highest on record.21,22 Some of the hardest-hit areas were just outside the Chesapeake Bay watershed. For example, the Roanoke, Virginia, area saw record-setting rainfall, and parts of the New River Valley experienced major flooding.23,24
A storm system impacted the region on April 7–9. During the late evening of April 7, two inches of hail accumulated on Interstate (I) 81 in August County, Virginia, contributing to several automobile accidents.25 On the morning of April 8, strong winds from thunderstorms snapped and downed numerous trees in West Virginia, Maryland, and northern and western Virginia, with some of the trees landing on houses and cars.26 Storm reports from this event indicate that a trailer collapsed after its roof was blown off in Harpers Ferry, West Virginia; shingles were torn from a house in Leesburg, Virginia; and a communications tower was damaged near Ingalls Field Airport, Virginia.27 This storm system also produced damaging non-thunderstorm wind gusts on April 9, blowing roofs from buildings in Dauphin County and Cumberland County in Pennsylvania.28
On April 13, a strengthening low-pressure system produced damaging winds across the watershed. Gusts of 40–60 miles per hour (mph) were common throughout the region, with some of the highest gusts reaching 75 mph in Moosic, Pennsylvania; 74 mph in Norfolk, Virginia; and 73 mph at a maritime station in Cape Henry, Virginia.29 This system also generated severe thunderstorms in portions of Pennsylvania, Delaware, Virginia, and Maryland, including two tornadoes—EF-0 and EF-1, respectively, on the Enhanced Fujita scale—that snapped trees and damaged homes in Caroline County and Carroll County in Maryland.30 The thunderstorm and non-thunderstorm winds associated with this system downed trees and wires, some of which fell on homes and cars, leaving thousands across the region without power.31,31 A strong wind gust even caused a tractor-trailer crash that left the cab dangling over the side of the High Rise Bridge on I-64 near Chesapeake, Virginia. The driver was rescued by members of the Chesapeake Fire Department after sustaining non-life-threatening injuries.33 Additionally, portions of central Maryland and central and western Virginia received more than 3 inches of rain, leading to road flooding.34 As a result, April 13 was one of the ten wettest April days on record for Dulles International Airport in Virginia and Washington, D.C.35
Photo by Chesapeake Fire Department, Virginia. (Posted to Twitter April 13, 2020)
Warmer temperatures throughout March contributed to below-normal snowfall for many areas. Scranton and Williamsport, Pennsylvania; Baltimore, Maryland; and Washington, D.C. all set or tied their records for the least snowfall in March. This March was also the first time on record with no measurable snow in Harrisburg, Pennsylvania.36 However, cool conditions returned in May, causing parts of the watershed to experience snowfall. For instance, Binghamton, New York, had its eight-snowiest days on record on May 8 and May 9, with 0.5 inches of snow on each day, helping the city have its sixth-snowiest May on record. 37
Generally, the Chesapeake Bay watershed saw below-normal snowfall this spring. Washington D.C.; Baltimore, Maryland; and Dulles International Airport all tied their records for least snowy spring, while Harrisburg, Pennsylvania, had its third-least snowy spring.38 It was only the third year on record that Washington, D.C., and Baltimore, Maryland, recorded no snow during the spring.39
According to the National Aeronautics and Space Administration (NASA), “…the data indicate that the nitrogen dioxide levels in March 2020 are about 30% lower on average across the region of the I-95 corridor from Washington, D.C. to Boston than when compared to the March mean of 2015–19.” 40 In fact, this spring, the Washington, D.C., area saw some of its best air quality in more than 20 years.41 Other areas, including Richmond, Virginia, also have noted an improvement in air quality.42 The lower levels of pollution this spring were attributed to the confluence of decades of environmental regulations; a wet, windy weather pattern; and a reduced number of vehicles on the road, because of stay-at-home orders that were in place throughout the region during the coronavirus disease 2019 outbreak.43
Part 2: Seasonal Temperature and Precipitation
Figure 1 shows the spring 2020 (March–May 2020) average daily temperature compared with the climate normal—i.e., the average daily temperature from 1981 to 2010.44 This figure indicates that the entire Mid-Atlantic region experienced spring temperatures within a few degrees of normal, with some small areas experiencing temperatures from 2°F below normal to more than 3°F above normal.
Figure 2 shows the spring season’s variability in daily average temperature departures from normal at the Washington Dulles International Airport in Virginia. While the average seasonal temperature for the region was near normal, the daily temperatures showed large departures for normal. Overall, this spring ranked as one of the top 20 warmest on record at Dulles International Airport, Virginia, despite the lower than normal temperatures recorded in April and May. 45
From March 1–May 31, 2020, precipitation departures from normal, shown in Figure 3, show that the Mid-Atlantic region experienced a range of precipitation conditions, with the southeastern portion of the region experiencing slightly drier conditions than normal (75–100 percent of normal) and the northwestern portion of the region experiencing wetter conditions than normal (up to 150 percent of normal). Southwestern Virginia experienced the wettest spring by far, receiving over 200 percent of its normal precipitation in some areas.
More information on how recent precipitation and temperature compares to historical trends for the East Coast, including the Mid-Atlantic region, can be found using the Southeast Regional Climate Center’s Climate Perspectives tool.46
The weather conditions from this season, along with their impacts, are discussed in Part 1.
Part 3: Summer 2020 Outlook
Temperature and Precipitation
As of May 31, 2020, the NOAA Climate Prediction Center forecasts a 50–60-percent chance of temperatures above normal for the summer season for the majority of the Chesapeake Bay watershed. The precipitation forecast shows a 33–40-percent chance of precipitation above normal in the southern half of the watershed for June–August 2020 in the Mid-Atlantic region.47
The United States Seasonal Drought Outlook identifies how drought might change across the United States and categorizes areas by whether drought could develop or become more or less intense. As of May 21, 2020, the outlook indicates no tendency toward drought for the Mid-Atlantic region.48 The Mid-Atlantic has experienced severe to extreme droughts in the past, most notably in the mid-1980s, the late 1990s, and the 2000s.49
Atlantic Hurricane Outlook
Researchers at Colorado State University (CSU) have predicted an above-average probability for major hurricanes for the 2020 Atlantic hurricane season. As of April 2, 2020, CSU’s forecast anticipates 16 named storms and eight hurricanes for 2020, with a 45-percent chance of at least one major hurricane (category 3–5) making landfall on the eastern U.S. coastline.50 NOAA’s Climate Prediction Center, which issues a hurricane outlook for the Atlantic at the end of each spring season, is forecasting a 60-percent chance of an above-normal 2020 Atlantic hurricane season. NOAA’s outlook forecasts 13–19 named storms, six to ten hurricanes, and three to six major hurricanes.51 According to NOAA, “an average hurricane season produces 12 named storms, of which six become hurricanes, including three major hurricanes.”52
Part 4: Timing of Spring Temperatures
The timing of spring temperatures, including the date of last frost and the first spring days that cross warm-temperature thresholds, are important determinants of vegetative growth, including crops, as well as of ecosystem health. Spring temperatures help determine the timing of the first appearance of spring leaves and the timing of first bloom. Earlier or later onset of warm temperatures or late frost events can affect canopy development and the activity of insects, birds, and animals.53 The following figures provide detail on how the timing of spring temperatures has changed over time (Figure 4) and could change into the future (Figure 5). Specifically, these figures show decadal changes in (a) the date of last freeze, defined as the last day in the first half of the year with a low temperature at 32°F or below; and (b) the first warm day, defined as the first date in a calendar year with a high temperature above 70°F or 80°F. These interactive tools can be used to generate local and regional insights into how the timing of spring temperatures has shifted over the historical record and might continue to shift in the future.
Figure 4. Historical Change in Date of Last Freeze and Date of First Warm Day
- In general, the southern portion of the Mid-Atlantic experiences the date of last freeze earlier than the northern half of the region.
- From 2000–2019, the region has seen an increase in the number of counties with dates of last freeze in February and a decrease in the number of counties with dates of last freeze in the spring months.
- The northern half of the region tends to see warmer temperatures later in the spring, with northern Pennsylvania and southern New York typically seeing their first warm day in March or April.
- Between 2011–2019, nearly the entire region experienced the first warm day in February or March.
How to Use the Tool
Selecting time periods: Use the slider under each map of the region to adjust the decade used to calculate the average month displayed for each metric.
Viewing variability within a county: Hover or tap over a county of interest. A window will pop up that displays the percentage of dates for a given metric per month in each decade.
Figure 5. Future Projected Changes in Date of Last Freeze and Date of First Warm Day
- Future projections show that the region as a whole might experience the onset of warm spring temperatures 15–26 days earlier than normal by the end of the century, and the last day of frost 12–20 days earlier.
- Under both future-emissions scenarios, the southern portion of the Mid-Atlantic is projected to continue experiencing the date of last freeze earlier than the northern half of the region.
- Future projections indicate that the region could experience an increase in the number of counties with dates of last freeze in February and a decrease in the number of counties with dates of last freeze in May and June. This trend toward earlier dates of last freeze is stronger in the southern half of the region.
- In both high and low future-emissions scenarios, the majority of the southern half of the region might experience the date of the first 70°F day in January and the date of first 80°F day by March by the end of the century.
How to Use the Tool
Selecting time periods and future-emissions scenarios:
Use the slider to the right of the maps to adjust the 30-year period used to calculate the average month displayed for each metric. Users can also select the future-emissions scenario (Low or High Emissions).
Viewing variability within a county: Hover over or tap on a county of interest. A window will pop up that displays the percentage of dates for a given metric per month in each decade.
The Mid-Atlantic Regional Integrated Sciences and Assessments (MARISA) Seasonal Climate Impacts Summary and Outlook is a quarterly series produced by the MARISA program, a collaboration funded by NOAA through the RAND Corporation and researchers at Pennsylvania State University, Johns Hopkins University, Cornell University, and the Virginia Institute of Marine Science. This series draws information from regional climate centers, news and weather information, and regional-specific climate datasets for the benefit of policymakers, practitioners, residents, and community leaders in the Mid-Atlantic region. Projections of weather and climate variability and change in the Mid-Atlantic region come from the best available scientific information. For any questions or comments, please contact Krista Romita Grocholski at Krista_Romita_Grocholski@rand.org.
This edition of the MARISA Seasonal Climate Impacts Summary and Outlook was authored by Krista Romita Grocholski (RAND Corporation), Michelle E. Miro (RAND Corporation), Jessica Spaccio (Cornell University), Samantha Borisoff (Cornell University), Arthur T. DeGaetano (Cornell University), and Jordan R. Fischbach (RAND Corporation).
Climate normals, as defined by the National Oceanic and Atmospheric Administration (NOAA), are “three-decade averages of climatological variables including temperature and precipitation.” The latest climate normal released by NOAA is the 1981–2010 average. https://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/climate-normals#Return to text ⤴
More information on RCP 4.5 can be found in Allison M. Thomson, Katherine V. Calvin, Steven J. Smith, G. Page Kyle, April Volke, Pralit Patel, Sabrina Delgado-Arias, Ben Bond-Lamberty, Marshall A. Wise, Leon E. Clarke, and James A. Edmonds, “RCP4.5: A Pathway for Stabilization of Radiative Forcing by 2100,” Climatic Change, Vol. 109, 2011, pp. 77–94. As of June 8, 2020: https://doi.org/10.1007/s10584-011-0151-4Return to text ⤴
More information on RCP 8.5 can be found in Keywan Riahi, Shilpa Rao, Volker Krey, Cheolhung Cho, Vadim Chirkov, Guenther Fischer, Georg Kindermann, Nebojsa Nakicenovic, and Peter Rafaj, “RCP 8.5—A Scenario of Comparatively High Greenhouse Gas Emissions,” Climatic Change, Vol. 109, 2011, pp. 33–57. As of June 8, 2020: https://doi.org/10.1007/s10584-011-0149-y Return to text ⤴
More information on RCP 4.5 can be found in Thomson et al., 2011. Return to text ⤴
More information on RCP 8.5 can be found in: Riahi et al., 2011. Return to text ⤴