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The radar data used on the StormTrack Doppler Radar imagery comes from the WSR-88D NEXRAD Doppler Radar network owned by the National Weather Service. In most cases, our StormTrack Doppler Radar display will be focused on Alabama using the Birmingham NEXRAD Doppler Radar, located at the National Weather Service Birmingham local office in Calera, Alabama. Radar images update betwen every 4 to 10 minutes, depending on which operating mode the NWS has placed the radar on. "Precip modes" will update between once every 4 to 6 minutes, and "clear air mode" will update less frequently. While we strive to have the most up-to-date information possible, due to things out of our control (i.e., internet outages, radar outages, power outages, etc.), we cannot guarantee that the radar data will be completely up-to-date 100% of the time. Please refer to the timestamp at the bottom-right corner of the screen to make sure the radar image is up-to-date. When our StormTrack Doppler Radar display is malfunctioning or is somehow otherwise not staying up-to-date for unpreventable reasons, please refer to the Radar link at the right of this page for other sources of Doppler Radar data.
Some things to know while viewing Doppler Radar...
The radar data used on the StormTrack Doppler Radar imagery comes from the WSR-88D NEXRAD Doppler Radar network owned by the National Weather Service. In most cases, our StormTrack Doppler Radar display will be focused on Alabama using the Birmingham NEXRAD Doppler Radar, located at the National Weather Service Birmingham local office in Calera, Alabama. Radar images update betwen every 4 to 10 minutes, depending on which operating mode the NWS has placed the radar on. "Precip modes" will update between once every 4 to 6 minutes, and "clear air mode" will update less frequently. While we strive to have the most up-to-date information possible, due to things out of our control (i.e., internet outages, radar outages, power outages, etc.), we cannot guarantee that the radar data will be completely up-to-date 100% of the time. Please refer to the timestamp at the bottom-right corner of the screen to make sure the radar image is up-to-date. When our StormTrack Doppler Radar display is malfunctioning or is somehow otherwise not staying up-to-date for unpreventable reasons, please refer to the Radar link at the right of this page for other sources of Doppler Radar data.
Some things to know while viewing Doppler Radar...
- Intensities vary based on the current mode of the radar. Radar returns on a "light weather" day are sometimes amplified using "Clear Air Mode". This allows us to see even finer details in the atmosphere but the amplified signals can look very dramatic to a user.
- Ground clutter is a pattern of radar echoes from fixed targets around the radar. An example is the green spots that are sometimes around the NWS Doppler Radar site near Calera, Alabama. This happens when the radar beam is closer to the surface (closer to the actual radar site, because with increasing distance from the radar, the beam is higher above the earth's surface because of the earth's curvature) and hits inanimate objects such as hills, buildings, or tall trees.
- Anomalous propagation (A.P.) occurs when temperature or moisture gradients near the radar cause part of the radar signal to bend abnormally. The beam of the radar can be turned into the ground or can bend upward. Both types of A.P. can make it look like there are large areas of rain or snow falling right around the radar. A.P. is most often visible at night with high amounts of moisture. Yellow and green are the most common colors that show up on the Doppler during anomalous propagation. The false returns are most common during nighttime hours when cooler temperatures and more moisture is pumped into the atmosphere adding to the bending of the radar beam.
