The recent National Oceanic and Atmospheric Administration (NOAA) increase to the
number of storms expected over the Atlantic Ocean this season does not appreciably alter the National Capital Region’s (NCR) level of risk from hurricanes.
On August 8, NOAA announced a chance for an above-normal hurricane season, with an expected 10 to 17 storms. In May, NOAA originally predicted nine to 15 storms.
The change is mainly in reference to the number of category 1 and 2 hurricanes (winds of 74 mph or greater); there is no change to number of 3, 4, or 5 category hurricanes previously predicted (winds of 111 mph or higher).
According to the National Weather Service Baltimore/Washington Office, a forecast for an “active” or “quiet” Atlantic hurricane season has little bearing on whether the storms that develop in the Atlantic will track over the NCR.
Location of storm track cannot be determined weeks or months in advance.
Both landfalling hurricanes, and remnant storms that made landfall elsewhere in the nation, can be a risk to the NCR.
The NCR has the greatest risk of these storms from mid-August through mid-October.
Flash flooding is one of the threats to the NCR during hurricane season. Flash floods, also known as interior floods, occur when heavy rainfall cannot be absorbed by the ground and overwhelms the drainage system. Urban development, weather conditions, local landscape—such as soil, grass, or asphalt—and storm drainage capacity are all factors that contribute to flash flooding. Flash floods cause rainwater and sewage to flood basements and streets. Flash floods can occur at any time of the year, even when river elevations are normal. Additional hurricane season threats include tidal flooding, winds, and tornadoes.
Although the historic July 8 storm was not hurricane-related, it stands as an example of flash flooding impacts to critical infrastructure. Three to seven inches of rain fell in just an hour, impacting multiple transportation networks.
Multiple water rescues on roadways, notably on Canal Road in the District of Columbia.
Rushing stream water collapsed a roadway in a residential area in Potomac, Maryland.
Overwhelmed drainage systems caused cascading water from the ceiling at Virginia Square Metro in Arlington, Virginia.
Residents and businesses should check to see if they are in a potential flood zone and learn how to prepare for hurricanes. Also see NTIC’s Atlantic Hurricane Outlook and Flooding Threat in DC.