Warm spot IR signatures of severe weather in early spring thunderstorms

The enhanced-V severe weather satellite picture signature using the MB curve was described by McCann (1980). The enhanced-V storm by definition has a warm spot or a warm area downstream from the cold top. Much of the kinematics is given by Adler and Mack (1984) and Adler and Mack (1985). Fujita (1978) noted that warming of thunderstorm tops observed in satellite imagery was related to downbursts and occasionally tornadoes, but these warm tops are different from the enhanced-V. In the early spring, when the tropopause is usually low, the overshooting tops are not as evident or seen very clearly, nor is the cold part of the enhanced-V often seen clearly. Thus, in these early spring situations in which the maximum tops are in the dark gray or black part of the MB curve, the severe weather signature may be a light gray warm spot in the temperature range of -43.2 to -53.2°C. Four cases of light gray warm spots in which severe weather occurred will be presented here. We believe the same mechanism is occurring in these cases as the one that produced the more familiar enhanced-V as shown in Fig. 1. This storm produced damaging winds and flash flooding in Cherry and Keya Paha counties in north central Nebraska.