Case Study of the 12-13 November 2011 Windstorm in South Central Colorado

On 12-13 November 2011, a widespread windstorm struck south central Colorado. In most years south central and southeast Colorado experience windstorms along the east slopes of the various mountain ranges. The windstorm of 12-13 November 2011 was unusual because it was widespread and damaging winds occurred in locations which do not typically observe such winds. Damaging winds around 25 to 45 m/s occurred in the lee of the Sawatch Range (Collegiate Peaks), Sangre de Cristo Mountains, Rampart Range/Pikes Peak and the Wet Mountains. These mountains cover a total distance of about 250 km. Winds in excess of 40 m/s were observed in Stonewall, CO, which is in the lee of the Sangre de Cristo Mountains south of the Spanish Peaks, resulting in significant damage to some buildings. Residents in Stonewall indicate winds of this magnitude are rare and winds of this strength near Stonewall have not been reported since Pueblo became a NWSFO in 1995.

This case study will focus on what meteorological factors resulted in this event being widespread and strong versus the more typical isolated and less extreme event. The forecast office in Pueblo locally runs a version of the WRF model with a 4km inner nest. Output from this model will be presented and the usefulness of this model in forecasting this event will be examined.