What causes tornadoes to occur?
– Daniel Childers, El Cajon ANSWER: There are about 800 to 1,000 tornadoes a year in the United States. Most occur in the center and southeast of the country where warm, moist air from the Gulf of Mexico meets air masses from Canada or the Rocky Mountains. Tornadoes are most common in the spring and summer months. However, as we have seen recently in California, they can occur anywhere, at anytime of the year. Tornadoes usually develop from thunderstorms. Thunderstorms occur when warm, humid air rises and encounters a layer of colder air. This cools the warm air and causes the water vapor in it to condense into water droplets or freeze into ice crystals. Condensation and freezing release heat, which triggers more upward air movement and adds to the storm’s power. Tornadoes form between the rising warm air and the cooler air descending with the rain or hail. The strongest tornadoes are produced by supercells, large thunderstorms with cloud structures 1,000 cubic miles or greater. Normal
