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Comment by pbohun | Hacker News Reader

I haven't seen enough history to know if that's normal or not, but I can tell you that the center of each of those blue "clouds" is a nexrad radar station. It's view is a wide cone from the ground upwards (technically a set of cones from each of the radar's tilt angles).

It's quite possible there is some lower altitude fog/precipitation/something that is only visible to the radar at it's lower tilt angles. But that's just speculation.

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One of my weird hobbies is radar chasing storms, and all of that stuff is completely normal. NEXRAD is very sensitive, especially when it's in clear air mode (it has different modes depending on if it's raining in the area) and can pick up things like dust, birds, bats, and insects. There's also ground clutter from things like buildings, wind farms, and even cars.

The National Weather Service has a good brief explainer: https://www.weather.gov/iwx/wsr_88d

They also have an interesting PDF covering some of the more unique signatures you might see, though it's not exhaustive: https://www.weather.gov/media/btv/research/Radar%20Artifacts...

Does clear air mode pick up wildfire smoke? There has been an awful lot of that lately over the US from Canada and the West Coast.

These are base reflectivity images. Composite reflectivity products reduce the noise from around the radar stations. The old NWS Java site used to let you select between them. Raw base images seem to be unavailable on the modern moving maps.

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