Recognizing Radar Signatures

Now that I’ve confessed that I’m a storm-chaser wannabe meteorologist these days and faced just about as many “are you crazy?” speeches that you can imagine, I’m going to be adding some content about our storms that we chase as well as some storm related blog posts to this already totally random blog. Your first installation will be this evening.

The other night while we were out I was showing Bryan some different things on the radar that looked promising to me as we headed out in search of the perfect storm. I decided that radar signatures would be a good topic for this evening so I pulled down a few examples of things that peak my attention when looking at a radar. If this sort of thing interests you I highly recommend attending a storm spotter certification course when it’s in your area, they are very informative although they spend most of the time discussing cloud types and take for granted that many of us now have multiple weather radars in our chase vehicles now…

	Squall Line: When grouped in a vertical line (as shown to the left), multicell thunderstorms are often referred to as squall lines. Squall lines stretch over a hundred miles in length. On radar, they can appear as a single continuous line, or as a segmented line of storms.
	Bow Echo: Sometimes a squall line slightly curves outward, resembling an archer’s bow. When this happens, the line of thunderstorms is referred to as a bow echo. The bow shape is produced from the rush of cool air that descends from a thunderstorm downdraft. When it reaches the earth’s surface, it is forced horizontally outward. This is why bow echoes are associated with damaging straight-line winds, especially at their center or “crest.” Circulations can sometimes occur at a bow echo’s ends, with the left (northern) end being the most favored for tornadoes, due to the fact that air flows cyclonically there.
	Hook Echo: When storm chasers see this pattern on radar, they can expect to have a successful chase day. That’s because a hook echo is an “x marks the spot” indication of favorable locations for tornado development. It appears on radar as a clockwise, hook-shaped extension that branches off from the right rear of a supercell thunderstorm. (While supercells can’t be distinguished from other thunderstorms on base reflectivity images, the presence of a hook means the storm depicted is in fact a supercell). The hook signature is produced from precipitation that gets wrapped into the counterclockwise-rotating winds (mesocyclone) within a supercell storm.