Multi-Scale Simulations of the 26 August 2007 Northwood, ND EF4 Tornado

During the evening of August 26, 2007, a devastating tornado, occurring within a mesoscale region of severe thunderstorms in eastern North Dakota, struck the small community of Northwood. The tornado, which was estimated to be nearly 1.6 km (1 mile) wide by a National Weather Service post-storm survey team, was classified as a category EF4 storm and resulted in one fatality, 18 injuries and nearly $60 million in property damages.

As part of a larger effort, we are examining the utility of the Weather Research and Forecasting (WRF) model for representing the larger mesoscale environment as well as the fine-scale thunderstorm and tornado structure, via two-way quadruple-nested simulations at grid scales ranging from 6 km to 222 meters. Our suite of simulations includes free forecasts as well as forecasts utilizing various data assimilation approaches applied to conventional and remotely sensed data.

In this paper we present the results from this effort, including a discussion of the utility of assimilating the various data types via approaches currently available in WRF. We utilize conventionally available data for validation, as well as data from the WSR 88-D radar located at Mayville, ND, 30 km south of Northwood. We also briefly discuss the potential for improving the forecast of this tornado through ingesting unmanned aircraft system data into the simulations via WRF's data assimilation framework.