Combined Lightning and Thermodynamic Observations of the Destructive June 2012 Derecho

The June 2012 mid-Atlantic and Midwest Derecho was one of the most destructive and deadly fast-moving severe thunderstorm events in North American history. The derecho produced wind gusts approaching 100 miles per hour as it traveled more than 600 miles across large sections of the Midwestern United States, the central Appalachians and the Mid-Atlantic States on the afternoon and evening of June 29, 2012 and into the early morning of June 30, 2012. It produced hurricane-like impacts with little warning, including widespread damage and more than 20 deaths, and left millions without power for multiple days across the entire affected region. The storm produced the highest lightning rates over this region that Earth Networks has ever recorded. We present lightning rates together with continuous temperature and moisture profiles observed by microwave radiometers, and derived forecast indices, along the storm path at locations in Iowa, Ohio and Maryland, providing unique perspective on the evolution of this historic storm. For example, an extreme CAPE value of 5,000 J/kg was derived from radiometer observations at Germantown, Maryland ten hours before storm passage, and 80 knot Wind Index (WINDEX) was derived seven hours before passage (see Figures). The Germantown radiometer is operated as part of the Earth Networks Boundary Layer Network (BLN) for continuous thermodynamic monitoring of the planetary boundary layer up to 30,000 feet. This case shows the correlation of high lightning rates with other measures of severe weather, and shows the utility of minute by minute real time data from lightning and radiometers.