Doppler velocity products indicate storm motion toward or away from the radar. The velocity products in RadarScope use the Doppler effect to determine how fast the particles in the air are moving relative to the radar itself. Negative values (green in RadarScope) indicate motion toward the radar, while positive values (red in RadarScope) indicate motion away from the radar. They can be difficult to interpret without training and experience, but Doppler velocity products can be used to detect the overall movement of a storm as well as relative motion within the storm itself, such as rotation. Note that the radar can only detect the component of the velocity vector along the radar beam, so this isn’t a full picture of the wind field. But it gives you a fairly good idea which way a storm is heading.
Super-Res Velocity
The super-res velocity product has a resolution of 0.25 kilometers by 0.5 degrees. It provides the highest-resolution reflectivity available from NEXRAD radars to a distance of 230 kilometers from the radar. Super-res velocity is available at four different tilts or beam angles, with tilt 1 being the lowest to ground level.
Super-Res Storm Relative Velocity
Super-res storm relative velocity is super-res velocity with the average storm motion subtracted out. When storms are moving quickly, this makes it easier to spot green/red velocity couplets that are indicative of rotation and which might be masked out by the motion of the storm. As with super-res velocity, green is motion towards the radar and red indicates motion away from the radar.
You can learn more about storm relative velocity on this expanded info article or on this National Weather Service page.
Super-Res Spectrum Width
Within any volume that is sampled by a radar, there can be a wide range of motions being observed. Spectrum width is a measure of that variation. Higher values of spectrum width correlate to a wider range of velocities being observed (turbulent flow; e.g. mesovortices); lower values indicate a narrower range (smooth flow; e.g. straight line winds). With proper interpretation, spectrum width can provide an indication of turbulence, which can be helpful in identifying conditions associated with severe thunderstorm activity.
Digital Velocity
Digital velocity is the standard velocity product distributed in the NEXRAD Level III product suite. It’s the same data as super-res reflectivity but at a lower resolution and larger coverage area.
Level II Velocity
Level II velocity is available to RadarScope Pro Tier Two subscribers. The Level II velocity product has a resolution of 0.25 kilometers by 0.5 degrees. It provides the highest-resolution reflectivity available from NEXRAD radars to a distance of 230 kilometers from the radar. Level II velocity includes all available tilts or beam angles, with tilt 1 being the lowest to ground level.
Level II Spectrum Width
Level II spectrum width is available to RadarScope Pro Tier Two subscribers. The Level II spectrum width product has a resolution as super-res spectrum width. It includes all available tilts or beam angles, with tilt 1 being the lowest to ground level.