The length of a hail spike is dependent on what factor?

The length of a hail spike is primarily dependent on the height of the hail core above ground level. This relationship arises from the physics of radar returns from hail. When radar waves pulse toward a hailstone, the distance they travel before reflecting back to the radar is directly influenced by the elevation of the hail core.

At greater heights, the radar signal encounters larger volumes of hailstones, which can result in a longer return signal or a hail spike on the radar display. The longer the distance the radar travels to reach the hail and return, the greater the observed length of the hail spike. This phenomenon is due to the fact that radar tends to capture the echo of the most intense reflectivity, which corresponds with the concentration and altitude of the hail core.

Other factors such as the diameter of the hailstones, the altitude of the radar, and the temperature of the atmosphere do play roles in the formation and dynamics of hail, but the specific characteristic of the hail spike length is most closely tied to the height position of the hail in the atmosphere.