When interpreting a radar velocity couplet, what does it indicate about the storm?

• A. A strong updraft.
• B. Clear sky.
• C. Static clutter.
• D. A couplet indicates strong rotation within a storm; signs of potential tornado formation; assess surrounding reflectivity and track.

Answer: (D)

A radar velocity couplet points to rotational motion inside the storm. When Doppler radar shows adjacent zones with opposing velocities that are very close together, it means air is spinning around a vertical axis in that part of the storm. That rotation is the signature of a mesocyclone and is a leading indicator of potential tornado formation. The reason this is the best interpretation is that velocity data directly reveals how air is moving toward or away from the radar, and a tight red-green couplet is the telltale sign of rotation, not just a strong updraft or clear skies.

As you interpret it, you should also look at the surrounding reflectivity pattern and the storm’s track. A hook-shaped reflectivity feature or a persistent, tightening couplet near the core increases tornado potential, whereas a random velocity pattern or a signature caused by clutter would not carry the same implication. Static clutter can sometimes mimic velocity features, so corroborating with reflectivity and storm motion helps confirm whether the rotation is real and poses a risk.