Chesapeake Bay Climate Impacts Summary and Outlook

Chesapeake Bay Watershed Climate Impacts Summary and Outlook: Spring 2019

Highlights

  • The Spring season saw a high number of tornadoes—nearly 40—across the Chesapeake Bay region, breaking records in many states.
  • Spring precipitation was up to double historical averages in the northern Chesapeake Bay.
  • Spring temperature was above average for most of the Chesapeake Bay watershed.
  • The region could expect normal to near-normal hurricane activity for the 2019 summer to fall hurricane season in the Atlantic Ocean.
  • An analysis of multi-decadal changes in seasonal precipitation shows that the region has experienced increases in summer seasonal precipitation, as well as increases in the variability of fall precipitation.
  • An analysis of future projections of seasonal total precipitation suggests that increased precipitation, compared to historical averages, could continue.

Part 1: Significant Weather Events

On March 21 and 22, a coastal storm brought snow and heavy rain to the region. Some areas received heavy rain, with the greatest 24 hour rainfall totals of up to 3.90 inches in southern Pennsylvania, Maryland, and northern Virginia.1 On March 21, Dulles Airport, Virginia, received 2.69 inches of rain2, its wettest March day on record (since 1960), which led to flooding, closed roads and stranded vehicles.3 Higher elevations received up to 10 inches of snow. A road in the Blue Ridge Mountains of Virginia was closed for several hours because dozens of vehicles became stuck due to snow and ice.4

On April 14 and 15, a severe weather outbreak occurred. Nine tornadoes touched down in Pennsylvania, five of which were in the Chesapeake Bay Watershed and included one Enhanced Fujita (EF) scale EF-0 tornado, three EF-1s, and one EF-2.5 In addition, there was one EF-0 tornado in Maryland, one EF-1 tornado in New York, and two tornadoes in Delaware, an EF-1 and an EF-2.6 The storms also produced straight-line winds7 of up to 105 mph, ping pong ball-sized hail, and over 2.50 inches of rain in some areas.8 Dozens of homes and buildings were damaged. Numerous trees were snapped and uprooted, and power lines were downed, leading to power outages and road closures.9

A few days later, on April 19, Virginia had its third largest single-day tornado outbreak with 16 tornadoes: nine EF-0s, four EF-1s, two EF-2s, and one EF-3.10 The EF-3 touched down in Franklin County, VA, the fourth recorded EF-3 tornado in the Blacksburg National Weather Service forecast area.11 In addition, five tornadoes, three EF-1s and two EF-2s, touched down in southern Pennsylvania; Fulton County had its first April tornado on record.12 Straight-line winds of up to 100 mph also occurred in the region. The storms damaged homes and other structures, destroyed outbuildings, and uprooted and snapped trees.13 Heavy rain caused flash flooding in parts of Virginia, closing some roads. With 14 tornadoes during April, Pennsylvania had its greatest number of April tornadoes since records began in 1950.14

A third round of severe thunderstorms downed wires and dozens of trees and caused damage to homes and buildings in the Mid-Atlantic on April 26.15 An EF-1 tornado touched down in north-central Maryland, mainly snapping and uprooting trees.16

On May 11, two EF-1 tornadoes touched down in Virginia, damaging trees and at least a dozen homes.17 An EF-1 tornado in south-central Pennsylvania on May 19 snapped and uprooted numerous trees, leading to a temporary closure of the Pennsylvania Turnpike.18 A few days later, on May 23, two tornadoes touched down in the region: an EF-0 in Pennsylvania and EF-1 in Maryland.19 Severe thunderstorms on May 25 and 26 produced a funnel cloud and golf ball-sized hail, as well as damaging wind gusts, in northern Virginia.20

From May 28 to 31, ten weak (EF-0 or EF-1) tornadoes touched down in the Chesapeake Bay region: eight in Pennsylvania and two in Maryland, accompanied by straight-line winds of up to 90 mph, softball-sized hail, and flash flooding.21 Storm reports indicated roofs were lifted off of several structures and hundreds of trees were downed, some of which fell on buildings.22 Pennsylvania had one of its most active Mays for tornadoes on record (since 1950), with 16 tornadoes.23 The state had 30 tornadoes during the spring season, which is six times greater than average.24

Part 2: Seasonal Temperature and Precipitation

Temperature

An analysis of Spring 2019 average temperature, shown in Figure 1, compared to the average from 1976 to 2005, indicates above-average departures from average historical temperature for most of the Chesapeake Bay watershed, including increases above 2°F in spring temperatures in the greater Baltimore metropolitan region and in western Virginia.

Figure 1. March 1, 2019–May 31, 2019 Departure from Historical Average March–May Temperature (°F)

Note: Historical average temperature is based on temperature data from 1976-2005. Red indicates above-average temperature.

Source: Northeast Regional Climate Center, 2019.

Precipitation

From March 1 through May 31, 2019, precipitation departures from average historical precipitation for the period 1976 to 2005 show that the region experienced both increases and decreases in precipitation compared to historical average precipitation, as shown in Figure 2. Western Virginia, southern and central Pennsylvania and northern Maryland experienced the highest rates of precipitation departures—up to 200 percent of the historical average. Southern Maryland and Eastern Virginia experienced decreases in precipitation up to 75 percent of average.

Figure 2. March 1, 2019–May 31, 2019 Percent of Average Historical March–Precipitation

Note: Historical average seasonal precipitation is based on precipitation data from 1976-2005. Brown indicates below-average seasonal precipitation.

Source: Northeast Regional Climate Center, 2019.

Part 3: Summer 2019 Outlook

Temperature and Precipitation

As of May 16, 2019, NOAA’s Climate Prediction Center forecasts a 40–60% chance of temperatures above normal for the majority of the Chesapeake Bay Watershed. The precipitation forecast shows a 33–40% chance of precipitation above normal in the Southern half of the watershed for June–August 2019 in the Mid-Atlantic region.25

Drought Incidence

The United States Seasonal Drought Outlook identifies how drought may change across the United States, and categorizing areas by whether drought could develop or become more or less intense. As of May 16, 2019, the outlook indicates no likelihood of drought for the Chesapeake Bay Watershed.26 The Chesapeake Bay region has experienced severe to extreme droughts in the past, most notably in the mid-1980s, the late 1990s and the 2000s. 27

Atlantic Hurricane Outlook

NOAA’s Climate Prediction Center, which issues a hurricane outlook for the Atlantic at the end of each spring season, is forecasting a normal hurricane season with 9–15 named storms, 4–8 hurricanes and 2–4 major hurricanes.28 Researchers at Colorado State University (CSU) have predicted an average 2019 hurricane season in the Atlantic. As of June 4, 2019, CSU's total seasonal forecast calls for 14 named storms and 6 hurricanes for 2019, with a 32 percent chance of at least one major hurricane (category 3-5) making landfall on the eastern U.S. coastline.29

Part 4: Seasonal Precipitation Trends and Projections

The following figures provide detail on how the total precipitation occurring each season has changed over time (Figure 3) and could change into the future (Figure 4). For a visual analysis of these changes across the Chesapeake Bay Watershed, please see Winter 2018-2019 Climate Summary.

Historical Change in Seasonal Total Precipitation

Key Findings

  • In general, the region has experienced increases in summer seasonal precipitation from 2006–2017 compared to historical averages, as well as increases in the variability of fall precipitation.

How to Use the Tool

Filtering by geography:
Using the dropdown menu, select a geographic level—the entire watershed, state, county or municipality. A list of states, counties or municipalities will appear, and individual locations can then be selected.

Technical Notes

The ChesWx gridded climate datasets contain daily interpolations of precipitation and temperature observations for the Chesapeake Bay watershed, as well as the broader Mid-Atlantic and surrounding regions. Data are available from 1948 to 2017 at 4km spatial resolution. For this study, we utilized ChesWx daily precipitation data over the Chesapeake Bay watershed from 1976 to 2017. Access ChesWx data and learn more about the ChesWx methodology and input datasets.

Seasonal total precipitation was determined for each season by summing all daily precipitation events that occurred for each three-month season. We calculated seasonal total precipitation for each season for each year and the averaged values for each season across 30-year periods – 1976-2005, 2006-2035, 2036-2065, 2066-2095 for LOCA data for both RCP 4.5 and RCP 8.5 and 1976-2005, 2006-2017 for ChesWx data. To average across climate models for each grid cell in the LOCA dataset, we employed a weighted average provided by the Northeast Regional Climate Center. Both LOCA and ChesWx datasets were masked to the boundaries of the Chesapeake Bay watershed before calculating seasonal precipitation values and the spatial resolution of each dataset was preserved. Winter is defined as December, January and February. Spring is defined as March, April and May. Summer is defined as June, July and August. Fall is defined as September, October and November.

Change in Future Seasonal Total Precipitation

Key Findings

  • All future time periods and emissions scenarios show increases in seasonal total precipitation in the winter, spring and summer across the Chesapeake Bay watershed.
  • Winter precipitation could increase by 1.2 inches in the Chesapeake Bay Watershed by the end of the century. Combined with projected changes in spring precipitation, heightened winter precipitation could lead to more dramatic spring flooding as snow melts and spring precipitation increase simultaneously.
  • Variability in future precipitation projections across the CMIP5 model ensemble is generally much greater than the average projected change, which is a limitation of model results.

How to Use the Tool

Selecting future time periods and emissions scenarios:
Use the slider to adjust the future time period used to calculate the projected change in precipitation. For each time period, the user can also select a future greenhouse gas emissions scenario under Future Emissions Scenario by selecting Moderate Emissions future, Representative Concentration Pathway (RCP) 4.530, or a High Emissions future, RCP 8.5.31

Filtering by geography:
Using the dropdown menu, select a geographic level—the entire watershed, state, county or municipality. A list of states, counties or municipalities will appear, and individual locations can then be selected.

Technical Notes

LOCA or Localized Constructed Analogs is a downscaled climate data product available at 1/16thdegree (6 km) resolution over the continental United States. LOCA datasets include the 32 climate models available in the CMIP5 archive, for two future greenhouse gas concentration trajectories – RCP 4.5 and RCP8.5. For this study, we utilized LOCA data over the Chesapeake Bay watershed from 1976-2095. Access LOCA datasets and learn more about the methodology.

Seasonal total precipitation was determined for each season by summing all daily precipitation events that occurred for each three-month season. We calculated seasonal total precipitation for each season for each year and the averaged values for each season across 30-year periods – 1976-2005, 2006-2035, 2036-2065, 2066-2095 for LOCA data for both RCP 4.5 and RCP 8.5 and 1976-2005, 2006-2017 for ChesWx data. To average across climate models for each grid cell in the LOCA dataset, we employed a weighted average provided by the Northeast Regional Climate Center. Both LOCA and ChesWx datasets were masked to the boundaries of the Chesapeake Bay watershed before calculating seasonal precipitation values and the spatial resolution of each dataset was preserved. Winter is defined as December, January and February. Spring is defined as March, April and May. Summer is defined as June, July and August. Fall is defined as September, October and November.

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The MARISA Seasonal Climate Impacts Summary and Outlook is a quarterly series produced by the Mid-Atlantic Regional Integrated Sciences and Assessments (MARISA) program, a collaboration funded by NOAA through RAND 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 Chesapeake Bay Watershed. Projections of weather and climate variability and change in the Chesapeake Bay Watershed come from the best available scientific information. For any questions or comments, please contact Krista Romita Grocholski at Krista_Romita_Grocholski@rand.org.

Footnotes

  1. https://www.weather.gov/lwx/pnsmap?type=rain&date=20190322&option=rain24 Return to text ⤴

  2. http://www.nrcc.cornell.edu/services/blog/2019/04/01/20190401_dulles.pngReturn to text ⤴

  3. https://www.ydr.com/story/news/2019/03/22/york-county-roads-continue-flood-close-friday/3243441002/ Return to text ⤴

  4. https://www.richmond.com/weather/storm-rainfall-swamps-some-roads-in-the-richmond-region-and/article_c7d0e989-ea2d-5bd1-b238-f6d1e9b9ab1e.html Return to text ⤴

  5. https://www.pennlive.com/news/2019/04/9-tornadoes-confirmed-across-pa-during-weekend-storms.html Return to text ⤴

  6. https://www.weather.gov/bgm/pastSevereApril152019 Return to text ⤴

  7. Straight-line winds damaging winds caused by weather events but are distinct from rotation-based tornado winds. For more information, see: https://www.nssl.noaa.gov/education/svrwx101/wind/ Return to text ⤴

  8. https://www.weather.gov/ctp/2019April14SevereReturn to text ⤴

  9. https://www.spc.noaa.gov/climo/reports/190414_rpts.html Return to text ⤴

  10. https://www.facebook.com/NWSWakefieldVA/posts/2178251425601420Return to text ⤴

  11. https://www.weather.gov/rnk/2019_04_19_Tornado Return to text ⤴

  12. http://www.nrcc.cornell.edu/services/blog/2019/04/23/index.htmlReturn to text ⤴

  13. https://www.spc.noaa.gov/climo/reports/190419_rpts.html Return to text ⤴

  14. http://www.tornadohistoryproject.com/tornado/Pennsylvania/April/tableReturn to text ⤴

  15. https://www.spc.noaa.gov/exper/reports/?&all&date=20190426Return to text ⤴

  16. https://www.weather.gov/lwx/MonktonTornadoReturn to text ⤴

  17. https://wtkr.com/2019/05/11/suffolk-officials-responding-to-suspected-tornado-damages/,
    https://www.weather.gov/rnk/2019_05_11_Tornado Return to text ⤴

  18. https://www.readingeagle.com/news/article/severe-storms-cause-injuries-home-damage-road-closures-in-eastern-lancaster-county Return to text ⤴

  19. https://wtop.com/local/2019/05/storms-leave-tornado-damage-in-howard-county/,
    https://www.pennlive.com/news/2019/05/crews-investigating-damage-from-tornado-in-cambria-county.html Return to text ⤴

  20. https://www.nbcwashington.com/news/local/Tornado-Warning-Issued-for-Fauquier-County-Northern-Virginia-May-2019-510432561.html Return to text ⤴

  21. https://www.weather.gov/bgm/pastSevereMay282019,
    https://www.weather.gov/lwx/survey05292019 Return to text ⤴

  22. https://www.spc.noaa.gov/climo/reports/190528_rpts.html Return to text ⤴

  23. https://www.ncdc.noaa.gov/stormevents/ Return to text ⤴

  24. https://www.spc.noaa.gov/wcm/ Return to text ⤴

  25. 17. https://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=1 Return to text ⤴

  26. https://www.cpc.ncep.noaa.gov/products/expert_assessment/season_drought.png Return to text ⤴

  27. https://onlinelibrary.wiley.com/doi/pdf/10.1111/1752-1688.12600 Return to text ⤴

  28. https://www.noaa.gov/media-release/noaa-predicts-near-normal-2019-atlantic-hurricane-season Return to text ⤴

  29. 20. https://tropical.colostate.edu/media/sites/111/2019/06/2019-06.pdf [PDF] Return to text ⤴

  30. More information on RCP 4.5 can be found in: Thomson, A.M., Calvin, K.V., Smith, S.J. et al. Climatic Change (2011) 109: 77. https://doi.org/10.1007/s10584-011-0151-4 Return to text ⤴

  31. More information on RCP 8.5 can be found in: Riahi, K., Rao, S., Krey, V. et al. Climatic Change (2011) 109: 33. https://doi.org/10.1007/s10584-011-0149-y Return to text ⤴

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