Chesapeake Bay Monster: An In-Depth Examination of the Baltimore Supercellular Thunderstorm of August 6, 2019

On an otherwise quiet weather day, a stationary supercell formed along the coastal environment of the Chesapeake Bay, directly over the City of Baltimore during the afternoon of August 6, 2019. This storm remained stationary over Baltimore for more than an hour, leading to measured wind gusts over fifty knots in two separate locations within the city twenty-four minutes apart. Quarter-size hail was also reported in the city. However, the greatest impacts were from torrential rainfall produced by the stationary storm. The Fells Point neighborhood of Baltimore received nearly a half foot of rain, leading to major urban flooding, and substantial property loss.

This study provides an overview of the storm’s impact across the city, including a detailed radar analysis of the storm from KLWX and TBWI, along with an examination of the pre-storm environment. Additionally, the study explores the unexpected nature of the storm. The poor forecasting of the stationary supercell along the bay breeze occurred on a day where conditions seemed unfavorable for severe thunderstorms or flash flooding across much of the Mid-Atlantic. Observed soundings (from IAD and WAL) were combined with RAP data/soundings and radar data to draw conclusions that could be applied to improve the analysis of the pre-storm environment, resulting in more effective and timely forecasts and warnings.