The succinct definition of radial velocity is "motion toward or away from Doppler RADAR". This radial component only considers the wind speed along the horizontal plane the RADAR is sampling and only the wind component relative to the radar. The radial velocity relative to the RADAR site is also called "base radial velocity". Use base radial velocity in a situation where the winds from a storm are moving in a straight line of action such as winds associated with a squall line or gust front. Computer algorithms can produce a storm relative radial velocity when the storm movement is combined with the base radial velocity. Storm relative radial velocity is the radial wind component relative to the storm. The magnitude of base radial velocity will depend on the speed a storm is moving toward or away from the RADAR and the wind motions within the storm moving toward or away from the RADAR. The storm relative radial velocity will subtract out storm movement and will thus give radial wind information that is completely related to wind motions within a storm and relative to a storm. Use storm relative radial velocity when assessing rotation in a storm. The faster a storm moves the greater the difference will be between the base and storm relative radial velocity. |