Convection Along Southern ZDC Surface Boundaries During Forecast Low Probability Severe Weather Avoidance Plan Days

Widespread afternoon and evening convection across the southern half of Washington Air Route Traffic Control Center’s (ZDC’s) airspace negatively impacts air traffic flow to and from the Caribbean and several of the busiest airports in the southeastern United States, including Hartsfield-Jackson Atlanta International Airport, Charlotte Douglas International Airport, Orlando International Airport and Miami International Airport. To avoid the convection, the Federal Aviation Administration may implement a Severe Weather Avoidance Plan (SWAP). On 30 days from April to October of 2015, 2016 and 2017, when a low probability (less than a 50% chance) of a SWAP was forecast by ZDC Center Weather Service Unit meteorologists, surface boundaries across the southern half of ZDC helped provide the focus for convection that resulted in a SWAP. This technical attachment describes and discusses different types of surface boundaries across the southern half of ZDC along which SWAP-causing convection developed and propagated on those 30 days. Also highlighted are other environmental factors that worked in concert with the surface boundaries to generate and maintain the convection.