What Weather Conditions Need to Be Present for a Tornado?

Meteorologists and storm chasers have long been fascinated by tornadoes. While they are difficult to predict, professionals can warn the public when conditions are favorable for them to form.

Origin

• Tornadoes form in thunderstorms along an unstable line separating air of different densities. Warm, moist air before eastward cold fronts frequently creates violent tornado-producing storms.

Storm Formation

• Dry lines of warm, moist east air and hot, dry air pushing from the west can create tornadoes, in addition to upward sloping air along mountain ranges and hurricanes and tropical storms, according to the National Severe Storms Laboratory.

Logistics

• A low, horizontal spinning effect forms as winds change directions, become faster and create an upward push. Meteorologists look for this aggressive rotation in systems through Doppler radar. The Storm Prediction Center reports that well-defined rotating storms (supercells) produce the deadliest tornadoes.

Signs

• Look for leaves, paper and other debris flying above the ground in a circular motion. If the air is warm and it is pitch dark with menacing walls of clouds, take safety and listen for loud, trainlike sounds. Hail, lightning, rain and strong winds are often present but are not predictors, according to the Storm Prediction Center.

Other Indicators

• Keep an eye on funnels from clouds and be aware some tornadoes are disguised by extensive rain and low-lying clouds. A drop in barometric pressure precedes tornadoes, which themselves contain such extreme drops that are difficult to measure.