Image: Brad Smull, NOAA
Wall cloud with lightning in Miami, Texas
Every child knows that converging warm and cool streams of air cause thunderstorms. But next time you notice a zeppelin-like structure forming below one of the cumulus clouds, beware – this might be a tornado in the making! Wall clouds, as pretty and dramatic as they may look, are often just the first warning sign, spelling out “RUN!” as clearly as they can.