Precipitation intensity is represented by a color scale, with green indicating the lightest rain, yellow as moderate rain, and orange and red representing the most intense rains falling at rates of up to 2 inches per hour. Magenta can be absurdly intense rainfall of up to 16 inches per hour, but usually it means hail. In the movie you may notice in early 2011 additional colors are added to represent wintry precipitation (blue & white for snow and pink for sleet or mixed rain/snow). This was due to an upgrade for NEXRAD, which added vertical polarization to the previous horizontal radar waves, allowing radars to better distinguish between rain and snow. The yellow and red outlines that keep popping up are severe thunderstorm watches and tornado watches, respectively (not to be confused with warnings!).

Doppler radar does have limitations. A radar beam spreads out with distance - becoming approximately 1000 feet wider for every ten miles of distance - resulting in decreased resolution when detecting distant precipitation. This is why a solid line of thunderstorms sometimes appears to break apart as it approaches a radar site: the line was never solid in the first place, but lack of resolution at a distance obscured that fact. Beam spreading can also make distant storms appear weaker than nearby storms because they return less of the radar beam’s energy. Another limitation stems from the fact that, due to the Earth’s curvature, a radar beam scans higher altitudes the farther it travels from the radar site, sometimes completely missing rain below it.

These limitations give NEXRAD radar an effective range of about 140 miles, so gaps in coverage are a problem. Some gaps are filled by privately-owned radars, but there are many remote areas that will never be fully covered, and there are even some heavily populated areas have a dangerous lack of radar coverage.

As you watch the time-lapse, you may sometimes notice what appear to be stationary blobs of rain centered on some radar sites. These blobs are not actually precipitation, but are instead caused by temporary atmospheric conditions like temperature inversions, fog, and variations in air density. This is an example of anomalous propagation. The aforementioned conditions can cause a radar beam to superrefract or duct through the atmosphere. When this happens, the beam will sometimes bend downward causing some of the radar energy to hit the ground and return energy back to the radar, which shows up as a false echo.

There are lots of other things that can show up on Doppler radar, some as real echoes, and some as false echoes. Here are a few:

bird roost rings:
These are common on late summer and autumn mornings where birds flock in and around bodies of water. Just before sunrise there is often a coordinated lift-off and dispersion of the birds into surrounding areas for feeding during the day. A similar phenomenon can be seen at dusk when large bat colonies take flight. Many other kinds of airborne objects can reflect radar energy and show up as echoes on your screen, including insect swarms, other kinds of insect swarms, and plumes of smoke from buildings on fire.

wind farm interference:
If wind turbines are within line-of-sight of a Doppler radar and the blades are rotating, they can show up as a false precipitation signature. Algorithms are usually able to filter out many echoes caused by physical obstacles like hills and buildings because the energy reflected by them has no motion. But since turbines are moving, their reflected energy is interpreted as weather. This can even be caused by chairlifts in motion at ski areas.

sunrise & sunset spikes:
Twice a day, at sunrise and sunset, radar experiences interference from the electromagnetic energy emitted by the sun. NEXRAD operates in the microwave part of the spectrum (S band, to be specific) and some amount of the sun’s energy arrives in microwave wavelengths. When a radar dish points directly at the sun at sunrise and sunset, it’s hit by this microwave radiation. This is then displayed as a brief spike of (falsely) returned energy.

some significant timecodes in the movie:
0:01:07 - 2010 early February blizzard 'Snowmageddon' (the first of three major winter storms to hit the East that month)
0:04:00 - 2010 May floods in Appalachia
0:11:54 - 2010 December blizzard
0:15:55 - 2011 April 25-26 Tornado Super Outbreak
0:16:51 - 2011 May 21-26 tornado outbreak sequence (including the Joplin, MO tornado)
0:30:20 - 2012 June 29-30 derecho
0:34:15 - 2012 Hurricane Sandy
0:37:45 - 2013 early February nor'easter
1:13:43 - 2016 January blizzard
1:22:21 - 2016 Hurricane Matthew
1:33:06 - 2017 Hurricane Harvey
1:33:36 - 2017 Hurricane Irma
1:45:55 - 2018 Hurricane Florence
1:46:46 - 2018 Hurricane Michael
1:57:43 - 2019 Hurricane Dorian