Here’s something interesting about weather radar.
These are enhanced mosaics from NOAA’s NWS South Plains sector.
In this one from 1/8/2013, watch the top third of the loop carefully and you’ll see inbound streaks moving quite rapidly from northeast to southwest.
Now watch this one from 2/10/2013 and you’ll see them mostly in the top right quarter, this time flying rapidly from the west-northwest toward the east-southeast.
Finally, watch this one from today (2/12/2013) and you’ll see them streaking through the center of Texas down to the coast and into the Gulf of Mexico, again moving in a west-northwest to east-southeast direction.
These returns on weather radar show up almost every day. Trust me, as a weather nut I pay attention and see them almost every day.
So what are they?
The obvious answer is meteors given their speed, clustering, and (generally) unidirectional nature. I haven’t investigated this yet, so I’m asking as much as guessing.
They look like “sun spikes” being picked up by multiple stations at slightly different times (due to different longitude). These generally register right at sunrise or sunset. The top would be sunset and the bottom two are sunrise. They are inclined toward the south since it is winter, and will shift closer to true E-W as we approach the vernal equinox. I don’t know much about the exact mechanism behind them, something to do with waveform interference between radiation from the sun and the radio waves from the radar station I think.
One thing to try would be calculating their velocity from the distance they travel and the time between frames. If it’s close to the rotational velocity of the earth, it might be solar as Neil suggests. If much faster, maybe meteors. If a few hundred km/h, maybe aircraft.