More Radar Images
Storm Relative Motion
When the motion of storms are subtracted from the wind field, the result is a picture of the wind as if the storms were stationary. As in the case of all velocity images, red color indicates wind moving away from the radar with green color indicates motion toward the radar. (The radar is located in the center of the image.)
Small scale circulations, from which tornadoes often form, will typically be indicated by strong inbound wind located beside strong outbound wind relative to the radar. Mouseover the image (top image right) to see the area that requires further investigation.
The yellow dot in the center of the image is the radar's location. Notice the bright green region is beside the bright red region with the dividing line along a radial to the radar (yellow dashed line). This is one indicator that the storm appears to be rotating, called a supercell, and will be closely monitored by the NWS forecasters for possible tornado development.
Comparing the storm relative motion image with base velocity image helps identify the rotating storm. Mouseover the storm relative image (bottom right) to view the base velocity image. While the green inbound winds remain prominent, the outbound winds (in red) nearly disappear.
In fact, just judging from the base velocity image, it might appear that there is only a strong inbound motion of gusty wind produced by the thunderstorm. However, when the storm relative motion image is teamed with the base velocity there is a clearer picture of the weather situation indicating a rotating thunderstorm.