Early Spring Downburst Event in Oklahoma

During the afternoon of 10 March 2010, strong convective storms, triggered by an upper-level disturbance, developed over southwestern Oklahoma and tracked northeastward. The area of convective storms produced strong downbursts in the Oklahoma City area while tracking northeastward in the wake of a cold front. Although the temperature contrast across the front was weak, a sharp decrease in boundary layer moisture and increase in low-level wind speed were apparent over central and southern Oklahoma in the wake of the cold front. Strong solar heating and gradient winds behind the cold front resulted in the development and evolution of a deep convective mixed layer, especially in the Oklahoma City area. This favorable environment, characterized by steep sub-cloud temperature lapse rate, super-adiabatic surface layer lapse rate, and large vertical humidity difference, fostered intense convective storm downdrafts. This environment was effectively illustrated as a classic "inverted V" profile in the late afternoon GOES sounding in Figure 1.

Figure 1. 2200 UTC GOES sounding profile over Oklahoma City.

This sounding profile translated into a significant risk of downbursts as shown in the GOES imager microburst products in Figure 2. About one hour later, strong downbursts were observed north of Oklahoma City, near the center of the upper-level disturbance.



Figure 2. GOES imager microburst products at 2200 UTC.

Figure 2 shows two versions of the GOES microburst product. The McIDAS-V version (bottom), displays overlying NEXRAD reflectivity from Oklahoma City (TLX) and the downburst-producing convective storms north of Oklahoma City near 2300 UTC. The microburst product indicates moderate risk (yellow to orange shading, top, green to yellow shading, bottom) associated with a wind gust potential of 35 to 40 knots. About one hour later, the two strongest downbursts of the event were recorded at Guthrie (45 knots) and Marshall (44 knots) Oklahoma Mesonet stations. This event demonstrated the effectiveness of the GOES microbust products, especially in this environment more typical of the summer season over Oklahoma.