Chesapeake Bay Climate Impacts Summary and Outlook

Chesapeake Bay Climate Impacts Summary and Outlook for 2018

The MARISA Seasonal Climate Impacts Summary and Outlook is a seasonal series produced by NOAA’s Mid-Atlantic Regional Integrated Sciences and Assessments (MARISA) program that details seasonal weather and climate variability and change in the Chesapeake Bay Watershed. This series draws information from other regional climate centers, news and weather information, regionally-specific climate datasets and the best available science on projected future climate impacts to present useful information for Chesapeake Bay Watershed policymakers, practitioners, residents, and community leaders. This edition also includes an in-depth analysis on multi-decadal changes in extreme precipitation events, accompanied by interactive maps.

Part 1: Significant Weather Events

Between winter and summer 2018, extreme weather events caused a series of disruptions, delays and damages to the Chesapeake Bay Watershed. Of these, the most significant impacts to the region’ residents and businesses included: flooding; beach erosion; power outages; school cancellations; accidents and travel delays, such as road closures and suspended flights that led to increased transportation costs.1,2

Two severe storm events that impacted the broader Northeastern United States, including the Chesapeake Bay—the Central and Eastern Winter Storm in January 2018 and the Northeast Winter Storm in March 2018—made the National Centers for Environmental Information (NCEI) list of billion-dollar disasters for 2018. The Northeast Winter Storm caused widespread damage estimated at $2.2 billion, and the Central and Eastern Winter Storm totaled $1.1 billion in damage.

In the Chesapeake Bay Watershed, the following extreme weather events occurred from February through August 2018:

Heavy Rain Events

A digger alongside a washed-out section of road as a crew works to repair a road destroyed by flooding on May 31, 2018 in Ellicott City, Maryland. Photo by Howard County Government / Getty Images

A crew works to repair a road destroyed by flooding on May 31, 2018 in Ellicott City, Maryland.

Photo by Howard County Government / Getty Images

From February 10 to 12, 2018, heavy rain caused flooding and road closures in eastern Maryland. The largest storm total precipitation of 7.21 inches was reported at 6:00 a.m. on February 12 in Bay City, MD3. On June 22, Richmond, VA, observed its wettest June day and its second wettest day for any month on record, with 7.61 inches of precipitation in 24 hours4.

Due in part to heavy rain and flash flooding across the state, between May 21 and 22, three sinkholes appeared in Frederick, MD5, and another in Annapolis, MD, which closed part of Route 4506. On May 28, unrelenting rain led to serious flooding in Ellicott City, MD, where a flash flood emergency was issued by the National Weather Service as streets turned into raging rivers and communities were inundated.

On June 3, water levels rose by 4.4 feet in 24 hours in the Cacapon River in Morgan County, WV, prompting the governor to issue a state of emergency.7,8 Throughout June, persistent rainfall in northern and eastern Virginia delayed the planting of crops and flooded fields.9

During the month of July, Baltimore, MD received a record 16.73 inches of rain, which is 411 percent of normal precipitation.10 Williamsport, PA, Harrisburg, PA, and Dulles Airport, VA experienced their wettest July on record.11

Record Warmth

The combination of sunshine and a strong flow of warm air from the south pushed temperatures into record territory12 for numerous sites across the watershed on February 20 and 21.13 High temperatures generally ranged from the low 60s to low 80s (°F), which was up to 40°F above normal. On February 21, Dulles Airport, VA recorded a high temperature of 82°F, the warmest February and winter temperature on record.

From July 1-4, high humidity along with unusually warm temperatures resulted in heat indices over 110°F in Maryland and Virginia, prompting Excessive Heat Warnings to be issued by the National Weather Service.14

Nor’easters

On March 2, the first of several nor'easters15 impacted the region. Strong winds associated with the storm downed trees and power lines.16 A few days later on March 7, a nor'easter brought rain, heavy, wet snow, and strong winds.17 Flooded streets led to road closures. Another nor'easter moved through the region on March 13-14, bringing heavy, wet snow and strong winds. And then another storm on March 21 brought Washington, D.C.'s biggest snowfall of the year, which ranged from 4.1 to 7 inches across the greater metropolitan area. The March storms brought coastal flooding, beach erosion,18 power outages, numerous school cancellations, accidents and travel delays throughout much of the region. Disrupted travel led to increased trucking costs.19

Severe Weather

On April 15, an Enhanced Fujita scale EF3 tornado was confirmed in the Elon community in Amherst County, VA. A severe rainfall event on May 15 brought intense downpours, which caused flooding, trapped people in cars, and road closures and issuance of a flash flood emergency in Frederick, MD. 20

Part 2: Seasonal Temperature and Precipitation

An analysis of Summer 2018 temperature trends, compared to historical averages, indicates above-normal departures for most of the Chesapeake Bay watershed, including departures of 1-3°F in summer temperatures in the northern watershed.

Figure 1. June 1-August 31, 2018: Departure from Average Temperature (°F)

A heat map showing average temperature departure June-August 2018, Chesapeake Bay

Note: Normal average temperature is based on temperature data from 1981-2000.

Source: Northeast Regional Climate Center, 2018.

Between June 1 and August 31, 2018, precipitation departures from normal, historical precipitation show most of the region experienced increases in precipitation compared to historical normal precipitation. Northern Virginia, southern Pennsylvania and western Maryland experienced the highest rates of precipitation departures—between 150 and 200 percent of normal. Areas vulnerable to flooding in the southern reaches of the Chesapeake Bay—north of Cape Charles in Virginia—also saw precipitation nearly double, compared to historical averages during this period.

Figure 2. June 1-August 31, 2018: Percent of Normal Precipitation

A heat map showing percentage of normal precipitation, June-August 2018, for Chesapeake Bay

Note: Normal average temperature is based on temperature data from 1981-2000.

Source: Northeast Regional Climate Center, 2018

Part 3: Seasonal Outlook

NOAA Atlantic Hurricane Season Outlook 2018

NOAA’s 2018 Atlantic hurricane outlook 21,22 calls for a potentially below-normal season. For the entire hurricane season NOAA predicts “9-13 named storms (winds of 39 mph or higher), of which 4-7 could become hurricanes (winds of 74 mph or higher), including 0-2 major hurricanes (winds of 111 mph or higher).”23

The Atlantic hurricane season runs from June 1 through November 30, with a peak from mid-August to late October. The season has already experienced thirteen named storms, including Hurricanes Florence and Michael. 24

Drought Incidence

The U.S. Drought Monitor identifies areas of drought across the United States and categorizes them by level of intensity. As of September 6, 2018, the Drought Monitor indicates no drought for the Chesapeake Bay Watershed. North of the Chesapeake Bay, in New York, current conditions are abnormally dry, with portions of the region in moderate drought.

El Niño Watch

NOAA’s Climate Prediction Center, which monitors the likelihood of occurrence of El Niño and La Niña climate phenomena, has issued a El Niño Watch for fall and winter 2018. 25, 26 El Niño is a climate phenomenon characterized by a warming of the sea surface temperatures in the central and eastern tropical Pacific Ocean that leads to changes in weather across the globe. While this generally results in wetter winter weather, weather impacts to the Chesapeake Bay Watershed can be difficult to predict. The last marked El Niño took place in 2010 and caused significant winter snowfall in the Chesapeake Bay region, when nearly 77 inches of snow fell during the winter of 2009-2010.

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Part 4: Interactive Chesapeake Bay Watershed Precipitation Data Tool

The following figures are a unique regional analysis that provide detail on how the number days of extreme precipitation each year have changed over time (Figure 3a) and how they are expected to change in the future (Figure 3b). This information provides stakeholders, stormwater managers, urban planners and other decisionmakers with some guidance on how many extreme events can be expected. In areas where the number of extreme events is increasing, additional planning and actions may be needed to mitigate urban flooding and related damage.

How Has Extreme Precipitation Changed from 1976 to Present?

Key Findings

  • The eastern half of the Chesapeake Bay Watershed has experienced increases in extreme precipitation from 2006-2017 compared to historical averages.
  • We see greater changes in the number of extreme precipitation events when looking at larger events.
  • Much of the eastern portion of the watershed has seen double the number of days with extreme precipitation over 3 inches. These are the largest daily events in our analysis.
  • Decreases in extreme precipitation events over the western portion of the watershed could suggest drying or at least decreases in the magnitude and intensity of precipitation events.

How to Use the Tool

Move the slider to adjust the Daily Precipitation Threshold to show number of days with precipitation above a 1", 2" or 3" threshold.

Click or tap a grid cell to show trends in the number of annual extreme precipitation events. This data will change when a different Daily Precipitation Threshold is 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 spacial 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.

We calculated the number of days above 1 inch, 2 inch and 3 inch daily precipitation thresholds ofr each year across the Chesapeake Bay watershed using the ChesWx precipitation data product. The annual counts above these thesholds were then averaged across two periods: 1976-2005 and 2006-2017. The ChesWx were masked to the boundaries of the Chesapeake Bay watershed, and the spacial resolution of each dataset was preserved.

How Could Extreme Precipitation Change in the Future?

Key Findings

  • Nearly all future periods and future emissions scenarios show some increase in the number of days each year with precipitation above 1”, 2” and 3” thresholds.
  • By mid to late 21st century, the majority of the Chesapeake Bay Watershed could experience a doubling of annual extreme precipitation events over 2” and 3” compared to historical averages, under the higher emissions scenario.
  • This suggests the challenges the region already experiences with respect to urban and coastal flooding could be magnified and more frequent in the future.

How to Use the Tool

Select a Daily Precipitation Threshold to show number of days with precipitation above a 1", 2" or 3" threshold.

Use the Time Period slider to adjust the future time period used to calculate the projected change in precipitation. For each time period, select a future greenhouse gas emissions scenario of moderate future emissions that peak in 2040 and then decline (known as RCP 4.527) or high future emissions that rise to 2100 (known as RCP 8.528).

Click or tap a grid cell to shows trends in the number of annual extreme precipitation events. This data was calculated for each year of the analysis and will change as you select different metrics, years and future emissions scenarios.

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.

We calculated the number of days above 1 inch, 2 inch and 3 inch daily precipitation thresholds for each year across the Chesapeake Bay watershed using both the ChesWx and LOCA daily precipitation data products. The annual counts above these thresholds were then averaged across 30-year periods – 1976-2005, 2006-2035, 2036-2065, 2066-2095 for LOCA data for both RCP4.5 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.

This summary is the start of a series of climate summaries produced by MARISA for stakeholders, decisionmakers and water managers in the Chesapeake Bay watershed. For any questions or comments, please contact Krista Romita Grocholski at Krista_Romita_Grocholski@rand.org.

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Footnotes

  1. https://www.odysseylogistics.com/noreaster-03-07-2018/ Return to text ⤴

  2. https://www.usatoday.com/story/travel/flights/todayinthesky/2018/03/07/noreaster-2-100-flight-cancellations-and-counting/402344002/ Return to text ⤴

  3. https://www.weather.gov/phi/20180211_heavyrainfall Return to text ⤴

  4. https://www.ncdc.noaa.gov/sotc/national/201806 Return to text ⤴

  5. https://www.wusa9.com/article/news/local/maryland/new-sinkholes-in-frederick-put-focus-on-hazardous-geology-in-region/65-557172801 Return to text ⤴

  6. https://patch.com/maryland/annapolis/sinkhole-closes-section-defense-highway-2-weeks Return to text ⤴

  7. https://nwis.waterdata.usgs.gov/usa/nwis/uv/?cb_00010=on&cb_00060=on&cb_00065=on&cb_00095=on&cb_00300=on&cb_00400=on&format=gif_default&site_no=01611500&period=&begin_date=2018-6-02&end_date=2018-06-04 Return to text ⤴

  8. https://www.ncdc.noaa.gov/sotc/national/201806 Return to text ⤴

  9. https://www.ncdc.noaa.gov/sotc/national/201806 Return to text ⤴

  10. http://www.nrcc.cornell.edu/services/blog/2018/08/ Return to text ⤴

  11. http://www.nrcc.cornell.edu/services/blog/2018/08/ Return to text ⤴

  12. https://www.climate.gov/news-features/event-tracker/record-warmth-february-2018 Return to text ⤴

  13. https://www.climate.gov/news-features/event-tracker/record-warmth-february-2018 Return to text ⤴

  14. https://www.washingtonpost.com/news/capital-weather-gang/wp/2018/08/28/its-the-last-week-of-august-and-heat-advisories-cover-the-northeast/?noredirect=on&utm_term=.64898f531c57 Return to text ⤴

  15. https://www.climate.gov/news-features/event-tracker/nor’easters-pummel-us-northeast-late-winter-2018 Return to text ⤴

  16. https://pilotonline.com/news/local/weather/article_3ed13cf2-90d6-5e36-9faf-90bd924558a7.html Return to text ⤴

  17. https://www.washingtonpost.com/news/capital-weather-gang/wp/2018/03/07/coastal-flooding-from-noreaster-hits-old-town-and-annapolis/?noredirect=on&utm_term=.cf4c85fa3d24 Return to text ⤴

  18. https://blogs.agu.org/wildwildscience/2018/03/08/look-what-the-coastal-storms-have-done-to-the-chesapeake-bay/ Return to text ⤴

  19. https://www.drought.gov/drought/sites/drought.gov.drought/files/media/reports/regional_outlooks/NE%20Spring%202018.pdf Return to text ⤴

  20. https://www.wusa9.com/article/news/local/maryland/swift-water-rescues-across-frederick-co-after-severe-flooding/65-552445714 Return to text ⤴

  21. http://www.noaa.gov/media-advisory/noaa-to-update-2018-atlantic-hurricane-season-outlook Return to text ⤴

  22. As of August 9, 2018, NOAA’s Atlantic Hurricane Season Outlook indicates a 10 percent chance this season will be more active than normal, a 30 percent chance it will be near-normal, and a 60 percent chance it will be below-normal. Return to text ⤴

  23. http://www.noaa.gov/media-advisory/noaa-to-update-2018-atlantic-hurricane-season-outlook Return to text ⤴

  24. https://www.nhc.noaa.gov/gtwo.php Return to text ⤴

  25. The chance of El Niño occurring in the tropical Pacific is 60 percent by fall and 70 percent by winter. Return to text ⤴

  26. http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml Return to text ⤴

  27. 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 ⤴

  28. 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 ⤴