What is an isotach?

• A. An equal line of wind speed
• B. A line of equal humidity
• C. An equal line of temperature
• D. A line of equal pressure

Answer: (A)

An isotach is a line on a weather map that connects points where the wind speed is the same. This helps you see how wind speed varies across an area and to spot strong wind gradients, such as near a jet stream—the closer the isotachs are, the sharper the change in wind speed. It’s not about humidity, temperature, or pressure—that’s shown by lines of equal humidity (isohumes), equal temperature (isotherms), and equal pressure (isobars). For example, a line labeled with a certain value means every point along that line has that wind speed.