Wnem Radar (2024)

FAQs

How can you tell how fast a storm is moving on radar? ›

Velocity data is derived from the phase, or doppler shift of the returned energy. The radar's computers will calculate the shift and determine whether the precipitation is moving toward or away from the radar, and how fast, then apply a corresponding color to those directions and speeds.

Warm colors (red) / positive values indicate wind moving away from the radar (along a radial). Cool colors (green) / negative values indicate wind moving toward the radar. Purple indicates “range folding”— where the radar cannot determine the radial velocity. Velocity image of a large-scale weather system.

Shades of blue represent lighter precipitation while red and purple indicate heavier precipitation.

On a weather radar map, a tornado is usually indicated by a smaller area of red surrounded by a larger area of green. However, modern radar systems can also indicate debris balls, a sign of a tornado on the ground.

It has to do with the type and intensity of the precipitation. The colors are typically a spectrum. The greens indicate light or moderate rainfall. Yellow, orange, and red indicate moderate to heavy rainfall and can also indicate hail.

This often appears as a red area directly next to a green area as seen on the NWS image below. If the radar shows a strong area of rotation and a debris ball in the same area, it is a strong signature that there is a tornado occurring.

If the radar cannot determine (called Range Folding) inbound or outbound then it paints the wind in purple. For the meteorologist, velocity is important for determining areas of strong wind from downbursts or detecting the speed of cold fronts.

Target information is displayed by numerical values and vectors on the Radar screen. For the reading of vectors, they point in the direction of the target while the length of the vector indicates the speed of the target.

The WSR-88D is one of the most powerful and advanced Weather Surveillance Doppler Radar in the world. Since first being built and tested in 1988, it has been installed and used operationally at over 160 locations across the United States, including Alaska and Hawaii.

Red indicates the winds moving away from the radar whereas green displays the winds moving toward the radar. Brighter shades identify faster winds whereas darker shades show slower winds. Such maps typically indicate a tornado by a smaller area of red surrounded by a larger area of green.

How do you calculate how fast a storm is moving? ›

The basic technique for calculating the storm-relative velocity is to determine the component of the average storm motion toward/away from the radar for each azimuth and subtract that value from the measured radial velocity for each pixel along the azimuth.

The unit has a digital readout that displays the highest speed read during the second or two your vehicle passes through the beam. Most modern police radar units can also operate in a "moving mode," allowing the officer to determine a vehicle's speed even though the officer's own patrol vehicle is moving.

Rotation can be detected when there is a couplet of winds moving toward and away from the radar located right next to each other. This often appears as a red area directly next to a green area as seen on the NWS image below.