Sunday, 11 January 2009
Radar characteristics of tornado producing mini-supercell in Tropical Storm Erin (2007)
Phoenix Convention Center
During the 2007 tropical season, Tropical Storm Erin re-strengthened over Oklahoma after making landfall along the coast of Texas. This tropical storm produced a total of seven tornadoes in Texas and Oklahoma. Its first tornado in Oklahoma was within the range of the Multifunction Phased Array Radar (MPAR) in Norman, OK. Using a scanning strategy that updates every 43 seconds with 14 elevation angles, the MPAR allowed us to measure the physical characteristics of a tornado producing mini-supercell in a tropical cyclone environment. The physical aspects of this mini-supercell include a shallow circulation only 4.5 km in diameter extending through a depth of 3 km. The reflectivity signatures were more subtle than typical Great Plains supercells and maximum reflectivity values of 50-54 dBZ extend over a small area. Based on these criteria, this cell is consistent with previous studies. The most noticeable difference form recorded events is the sampling of this storm at such a high temporal resolution. A rapid intensification to tornadic over a three-minute period exemplifies the need for up-to-the-minute radar data. Using better sampling strategies and higher resolution will lead to an increased understanding of the hurricane-spawned tornado and improved forecast and warning accuracy.