What is a wall cloud? Why are they important to look for?
A wall cloud is defined as, “A localized, persistent, often abrupt lowering from a rain-free base”. Wall clouds can range from a fraction of a mile up to nearly five miles in diameter, and normally are found on the south or southwest (inflow) side of the thunderstorm. When seen from within several miles, many wall clouds exhibit rapid upward motion and cyclonic rotation. However, not all wall clouds rotate. Wall clouds are important to look for because a rotating wall cloud usually develops before strong or violent tornadoes, by anywhere from a few minutes up to nearly an hour. Wall clouds should be monitored visually for signs of persistent, sustained rotation and/or rapid vertical motion.
