Tornadoes form when unstable air in a thunderstorm creates a horizontal rotation in the clouds and strong downdrafts draw that vortex down to the ground. Overlapping fronts can trigger the wind shear necessary to initiate a tornado's rotation, which is why meteorologists issue watches whenever severe thunderstorms threaten. Tornadoes can form with very little notice and are particularly unpredictable and dangerous weather events.
When weather fronts clash, sometimes warm and cool air layers overlap at the boundaries. This can create strong updrafts and downdrafts, unpredictable winds that carry moisture and warm air into the various layers of the atmosphere. The temperature differences between these layers help trigger air movement, setting up the horizontal rotation high in a storm that can transform itself into a tornado.
Often, the only warning of a tornado is a sudden increase in wind shear. Meteorologists use Doppler radar systems to detect this wind shear, looking for particular signatures that can indicate the beginning of a tornado. The most common sign of a tornado's formation is a "hook echo," a spiral-shaped radar return that indicates clouds being wrapped around a vortex. In many cases, the National Weather Service announces a tornado warning based on one of these echoes before anyone has visually spotted the tornado.Learn More
Tornadoes are formed when warm air combines into storm clouds causing an updraft that mixes with a burst of colder air, which leads to rotation within the cloud. The down draft of cooler air causes the tornado to form, pulling more warm air from the ground. As the updraft strengthens, it mixes to create a spot of low pressure that pulls at the cloud's vortex and forms a funnel cloud.Full Answer >
According to the National Oceanographic and Atmospheric Administration, tornadoes form when warm air creates a rotating updraft in a powerful thunderstorm. When winds blow in sharply different directions or at different speeds in these storms, they can set up a rotation that feeds on itself, creating a condition called a mesocyclone. When this construct rotates and touches the ground, it becomes a tornado.Full Answer >
Hurricanes form when rising warm, moist air displaces colder air high in the atmosphere. The cold air drops down on all sides of the warm spot, swirling slightly as it falls, then becomes warm and moist itself, repeating the process. Over time, the swirling grows into a hurricane.Full Answer >
Obvious clues to look for that a thunderstorm is on the way include a static noise on an AM radio station, the smell of rain and a sudden drop in temperature along with a strong breeze. Other signs are a change in wind direction, billowing and darkening clouds, flashes of lightning in the distance or the faint sound of thunder.Full Answer >