2016 South Texas Bow Echo
Greg Heavener, National Weather Service, Corpus Christi, TX
During early morning hours on 19 March 2016 a large bow echo developed across the Brush Country of South Texas and raced eastward towards the Coastal Bend of South Texas. Corpus Christi International Airport recorded its fifth highest convective wind gust of 68 mph. A bit farther south across the heart of the city, a 78 mph gust was recorded at Naval Air Station Corpus Christi. Winds gusted to severe levels (50 knots) for nearly one-hour across the city causing more than one-half of a million dollars in damage and prolonged power outages during the city’s Spring Break festivities.
This bow echo was not forecast very well by any of the convection-allowing models (CAMs). We believe this was related to the CAMs failing to properly assess the strength of the low-level capping inversion and lack of environmental 0-3km shear. The low-level environmental wind shear, which helps to promote storm organization and intensity, was too weak to produce a defined bookend vortex. Though instability aloft with ample DCAPE showed the potential for strong to severe downbursts, CAMs continued to downplay the convection surviving as it neared the Middle Texas coast early in the morning on 19 March 2016. It is hypothesized that a southward moving outflow boundary intersecting this QLCS was able to aid in the mixing of stronger winds aloft down to the ground surface while helping to strengthen the low-level (0-3km) wind shear values.
This presentation will discuss the difficult forecast challenges using the CAM guidance, the potential reasons why the CAMs struggled, and what our office is doing to better forecast these high impact events.