Tropospheric scatter frequently explains VHF/UHF communications well beyond the radio horizon. What makes this propagation mode possible?

Tropospheric scatter occurs in the lowest layer of the Earth's atmosphere (the troposphere), which is where all of our weather happens. It is driven by small variations in temperature, humidity, and pressure that subtly bend and scatter VHF and UHF radio waves, allowing them to propagate well beyond the normal visual radio horizon. Distractors mentioning ionized patches or daytime D-region ionization refer to the ionosphere, which primarily affects HF signals, not VHF/UHF in the troposphere. Local cloud cover alone does not create the necessary refractive index variations to cause consistent over-the-horizon scatter.