Chesapeake Bay Climate Impacts Summary and Outlook
Mid-Atlantic Regional Climate Impacts Summary and Outlook: Fall 2020
- This fall saw a wide range of precipitation conditions; the northern portions of the Chesapeake Bay watershed had an abnormally dry season, while the southern and eastern portions of the watershed experienced above normal precipitation. These patterns continued from the summer season.
- The majority of the Mid-Atlantic region experienced higher than normal temperatures, particularly due to a warmer than average November.
- This fall ranked among the five warmest on record for Scranton, Pennsylvania; Dulles Airport and Norfolk, Virginia; and Salisbury, Maryland.
- Post-tropical cyclone Sally, Tropical Storm Eta and Tropical Storm Zeta interacted with frontal systems to produce heavy rainfall in portions of the Mid-Atlantic this fall.
- Hurricane Isaias and Tropical Storm Fay were the most damaging storms to reach the Mid-Atlantic region in the 2020 hurricane season.
- In the Mid-Atlantic, the years from 2000–2020 saw nearly twice as many hurricanes as the preceding two decades—1980-2000.
Part 1: Significant Weather Events and Impacts
Washington Dulles International Airport, Virginia (Dulles Airport) recorded two of its warmest minimum temperatures on record for September with a low of 72°F on September 2 and a low of 74°F on September 10.1
This October ranked among the 10 warmest on record for Dulles Airport and Norfolk, Virginia, and among the 20 warmest for Richmond and Lynchburg, Virginia, and Salisbury, Maryland.2
Parts of the region experienced unusually warm temperatures from November 8–11.3 Daily highs in the 70s and 80s ranked among the five warmest days for November for Norfolk, Virginia, and among the ten warmest days for November for Scranton, Pennsylvania.4 On November 11, low temperatures were generally in the 60s, with Lynchburg and Charlottestville, Virginia, recording their warmest low temperature for November.5 Additionally, lows at Scranton, Pennsylvania, and Norfolk, Virginia, ranked among the five warmest for November and at Dulles Airport lows ranked among the ten warmest for November.6
November ranked among the five warmest on record for Scranton and Harrisburg, Pennsylvania; Baltimore and Salisbury, Maryland; Dulles Airport, Norfolk, Richmond, and Lynchburg, Virginia; and Washington, D.C. 7,8 It was among the 10 warmest Novembers on record for Binghamton, New York, and among the 20 warmest for Williamsport, Pennsylvania, and Martinsburg, West Virginia.9,10
Overall, this fall ranked among the five warmest falls on record for Scranton, Pennsylvania; Dulles Airport and Norfolk, Virginia; and Salisbury, Maryland; among the 10 warmest for Harrisburg, Pennsylvania; Baltimore, Maryland; and Lynchburg and Richmond, Virginia; and among the twenty warmest for Williamsport, Pennsylvania; Binghamton, New York; and Washington, D.C.11,12
Above normal temperatures that occurred during the fall season were in part characterized as a ‘second summer’, which is a period of unseasonably warm fall temperatures that occur every two to four years in the Mid-Atlantic region.13
Abnormally dry to severe drought conditions were present during the fall season in portions of Pennsylvania and New York.14
Residents in nearly half of Pennsylvania’s 67 counties were asked to voluntarily reduce their water usage in September, with some regional and local water suppliers enacting restrictions.15 The dry conditions also affected agriculture. For the week ending September 27, 27% of Pennsylvania’s corn crop was rated poor to very poor by the United States Department of Agriculture (USDA), one of the worst corn condition ratings in the country for the week.16, Due to variable conditions across the state, yields of corn and soybeans were reduced in some locations, particularly in the central portions of the state.17,18 The dry conditions also led to an increased wildfire risk in Pennsylvania.19
Precipitation was highly variable throughout the region this fall with records set for both wet and dry periods.
Binghamton, New York, had its 19th driest September on record, while Richmond, Virginia, had its 13th wettest and Norfolk, Virginia, had its 19th wettest.20 This October ranked among the 20 wettest on record for Richmond and Lynchburg, Virginia, and Salisbury, Maryland.21
November ranked among the five wettest on record for Norfolk and Lynchburg, Virginia, and among the ten wettest for Baltimore and Salisbury, Maryland; Charlottesville, Virginia; and Washington, D.C.22
Lynchburg, Virginia had its wettest fall on record.23, The season also ranked among the ten wettest on record for Washington, D.C. and Norfolk and Richmond, Virginia; and among the twenty wettest for Baltimore and Salisbury, Maryland.24,25 In contrast, Williamsport, Pennsylvania experienced one of its twenty wettest falls on record.26
Severe thunderstorms produce flooding rains and damaging winds, which downed trees and wires in central and southern Maryland on September 3.27 Additionally, an Enhanced Fujita Scale (EF) EF-1 tornado uprooted and snapped trees and damaged a few homes in Edgewater, Maryland.28
On September 9 and 10, heavy rainfall led to flash flooding in parts of Maryland and Virginia. Isle of Wight County, Virginia, received more than 6 inches of rain in 24 hours.29 This amount of rain left multiple roads impassable or washed out and some schools and houses partially flooded.30,31 As much as 5 inches of rain fell on September 10 in Washington, D.C. and some neighboring suburbs.32 Across the affected areas, there were numerous road closures, dozens of stranded vehicles, and several water rescues.33 The heavily-traveled Route 50 in Prince George’s County, Maryland, ended up under 5 feet of water and was shut down for around 6 hours.34 Basements also took on water, and in Washington, D.C.’s Edgewood neighborhood, an overwhelmed wastewater drainage pipe caused sewage to back up into some homes.35 The heavy rainfall also caused waterways to rise rapidly, with a stream gauge near Colesville, Maryland, rising eight feet in about an hour.36
Areas of New York and Pennsylvania were experiencing one of their 10 driest Septembers on record until the last two days of the month—September 29 and 30, when a storm system dropped up to three inches of rain to these areas.37 Two EF-0 tornadoes associated with this system damaged trees and a few structures in southeastern Virginia.38
A storm on November 30 dropped up to three inches of rain on the region, with Baltimore, Maryland having its fifth wettest November day on record and Washington, D.C. having its sixth wettest. 44 Flooding led to some road closures and water rescues in portions of Maryland and northern Virginia.45,46 Additionally, two tornadoes touched down in northern Maryland, an EF-1 that snapped and uprooted trees in Cecil County and an EF-0 that destroyed several barns in Caroline County.47,48
From September 17-18, post-tropical cyclone Sally interacted with a frontal system and produced 2-6 inches of rain in central and southern Virginia, with a maximum of 6.59 inches in Northampton County, Virginia.49 The primary impact of this rainfall was flooded roadways.50
From October 10-12, the remnants of Hurricane Delta and a frontal system produced up to three inches of rain, which particularly impacted Virginia.51
From October 29-30, Tropical Storm Zeta and another storm system moved through the Mid-Atlantic, bringing widespread rain to the region. The greatest rain totals topped three inches, with a maximum of 5.62 inches falling in Appomattox, Virginia.52 This rainfall flooded portions of Virginia and Maryland and led to road closures.53 Wind gusts of 40-50 mph were recorded in Maryland and Virginia, where downed trees and power outages were reported.54,55 Additionally, colder air on the northern side of the storm caused up to 2.5 inches of snow to fall in northern Pennsylvania and south-central New York.56
On November 11-12, a frontal system fed by tropical moisture from the Atlantic Ocean and Tropical Storm Eta brought heavy rain to Virginia and Maryland. The greatest rain totals from this system ranged from 6 to 8 inches.57 Resulting flash flooding caused multiple road closures.58 Riverine flooding also occurred. Preliminary data shows that the St. Mary’s River at Great Mills, Maryland reached major flooding stage and recorded one of its 10 highest levels since the 1940s.59
Part 2: Seasonal Temperature and Precipitation
Figure 2 shows the September–November 2020 average daily temperature compared with the climate normal—i.e., the average daily temperature from 1981 to 2010.60 The figure shows that almost the entirety of the Mid-Atlantic region experienced above normal temperatures during the fall season, with the southern portion of the Delmarva Peninsula experiencing particularly higher than normal temperatures. Only isolated areas had temperatures that were within a degree of normal. This is a continuation of the trend seen in the Summer 2020 Mid-Atlantic Climate Impacts Summary.
Precipitation departures from normal for September 1–November 30, 2020 are shown in Figure 3. Departures from normal indicate where this fall season’s average daily rainfall was above or below the average daily fall season precipitation from 1981 to 2010. Figure 3 shows that the Mid-Atlantic region experienced a large range of precipitation conditions, with northern and western portions of the region experiencing significantly less than normal precipitation and southern and eastern portions of the region experiencing significantly more than normal precipitation. Central Pennsylvania was particularly dry, experiencing 50-75% of normal rainfall, while spots on the Delmarva Peninsula and in southeastern Virginia experienced over 200% of normal rainfall. This northwestern/southeastern divergence in precipitation conditions is similar to the to the pattern seen during the summer 2020 season.61
Part 3: Winter 2020-2021 Outlook
Temperature and Precipitation
As of November 19, 2020, the NOAA Climate Prediction Center forecasts a 33–40-percent chance of above-normal temperatures for winter for the majority of the Chesapeake Bay watershed and Mid-Atlantic region.62 The precipitation forecast shows an equal chance of precipitation above, at, or below normal for December 2020 through February 2021 for Maryland, eastern Pennsylvania and northern and western Virginia, and a 33–40-percent chance of wetter than normal conditions in western Pennsylvania and southern New York and a 33–40 percent chance of precipitation below normal in southeastern Virginia.63
The U.S. 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 November 19, 2020, the outlook indicates that drought removal is likely to persist in central Pennsylvania. It shows no tendency toward drought for the rest of the Mid-Atlantic region.64
Climate Circulation Patterns
NOAA’s Climate Prediction Center, which monitors the likelihood of occurrence of El Niño and La Niña climate phenomena, has a La Niña Advisory active as of November 12, 2020 with a 95% chance to continue during Winter 2020-2021.65 La Niña episodes have generally resulted in average to slightly above averages temperatures and below normal rainfall and precipitation during December, January and February in the Mid-Atlantic region.66
Part 4: Mid-Atlantic Hurricane Tracks
The 2020 Hurricane Season, which officially came to a close on November 30, produced the most named storms on record with a total of 30 named storms, 13 of which were hurricanes and six of those major hurricanes (Category 4 or greater).67 This surpassed the last record year of 2005, which had 28 named storms and included Hurricanes Katrina and Rita.68 Twelve of 2020’s named storms hit United States coastlines, with every part of the U.S. Atlantic coastline under a related watch or warning at various points in time during 2020.69 The Mid-Atlantic coastline saw tropical storm watches and warnings for storms Fay and Isaias.70 Tropical Storm Fay, which made landfall near Atlantic City, New Jersey, resulted in approximately $350 million in damage and six reported deaths, and brought high winds and heavy rain to the Mid-Atlantic.71, Category 1 Hurricane Isaias produced an estimated $5 billion in damage after making landfall in North Carolina and traveling up the eastern United States coastline where it produced multiple tornadoes, damaging winds, and flooding rains.72,73
MARISA has previously created data tools to examine the reported crop and property damage from tropical storms and hurricanes in the Mid-Atlantic74 as well as their frequency and intensity over time.75 Figure 4 builds upon these analyses and shows the number of tropical storms and hurricanes crossing the Mid-Atlantic from 1980–2020.
Although the Mid-Atlantic is also affected by remnants of hurricanes and tropical storms or the regional effects these storms produce, Figure 4 only includes storms whose tracks directly overlapped one of the states in the Mid-Atlantic region. For example, the precise track of Tropical Storm Fay did not cross the boundaries of the Mid-Atlantic and is not shown in the map below. Tropical Storm Fay can be viewed in the NOAA Historical Hurricane Tracks Viewer.
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 data sets 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 Michelle E. Miro (RAND Corporation), Krista Romita Grocholski (RAND Corporation), 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. See https://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/climate-normals#:~:text=Climate%20Normals%20are%20three%2Ddecade,variables%20including%20temperature%20and%20precipitation Return to text ⤴
For more information on how NOAA defines at, above or below normal and determines percent chances, see: https://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal_info.php Return to text ⤴
The Mid-Atlantic has experienced severe to extreme droughts in the past, most notably in the mid-1980s, the late 1990s, and the 2000s.
https://onlinelibrary.wiley.com/doi/pdf/10.1111/1752-1688.12600 Return to text ⤴