What really happened in Altona?

On Friday, March 6, 2009 between 0930 and 1000 EST, a wind turbine collapsed at the Noble Environmental Power wind park in Altona, Clinton County, NY, setting off a fire and posing a question about the cause of the turbine collapse. High winds were reported throughout that region (the so-called “North Country” of New York State) on that day, but there were no publically available data from meteorological stations located in close proximity that could provide adequate information on weather conditions before, during and after the collapse. While a thorough investigation is still to be completed, high-resolution, near-surface atmospheric simulations can help to understand any weather-related contributions to such an incident. They can also support risk analysis and potentially lead to a more optimal design, siting and operation of wind farms. To demonstrate the application and utility of high-resolution numerical weather models, a set of WRF-ARW model ensemble runs have been performed for the time of this event. Ten ensemble members were initialized from two different larger scale models and were evolved using various physics parameterizations. Ensemble variability of resulting winds at the time of the incident were analyzed. A disturbance associated with increased low-level vorticity and wind shear is shown to pass through location of the wind farm prior to the time of the incident. Simulations were validated against atmospheric soundings from locations within a 250 km radius of the turbine site, as well as using observations from surface sites.