sunnuntai 2. lokakuuta 2016 22.49.17 UTC+3 Martin Gregorie kirjoitti:

Do any of you know more about this? Esp the frequency the radar used and
how/why it detected thermals.

Insects are sucked to thermals from close to ground. These are roughly same size as rain or snow coming down from clouds, so they are visible in weather radar images accordingly, as are birds and larger objects. I believe weather radars operate in centimeter scale wavelength.