What indicators might suggest that a tornado is forming?

The formation of a tornado is often indicated by specific atmospheric conditions and visual cues. A rotating, horizontally oriented cloud base, along with rapidly changing winds, are classic signs associated with the development of tornadoes.

When severe thunderstorms, particularly supercells, begin to rotate, the cloud base may take on a horizontal orientation as part of the mesocyclone. The presence of high wind shear, where different layers of the atmosphere have varying wind speeds and directions, contributes to the development of rotation. Rapidly changing winds at various altitudes can enhance this rotation, making tornado formation more likely as conditions become conducive for intense updrafts and down drafts.

In contrast, a sudden increase in temperature combined with clear skies may suggest stable conditions rather than severe weather. Persistent rain and steady winds usually indicate the presence of a more stable system, not one conducive to tornado formation. Lastly, strong high-pressure systems are typically associated with calm and clear weather, which is also not favorable for the development of tornadoes.

Thus, the first answer accurately reflects the signs that meteorologists and storm chasers look for when assessing the risk of tornado formation.