Reading the updraft base

StriationsGrooves or channels in a cloud, arranged along the airflow, that often reveal rotation. The corkscrew or barber-pole look on a low-precipitation supercell updraft is the classic example.: the updraftThe column of rising air inside a storm. Everything a thunderstorm does, from hail to tornadoes, is downstream of how strong and how organised this is. showing its own rotation

Striations are horizontal banding wrapped around the updraft tower, and they are one of the few cues that says "rotating" before anything has lowered. The extreme version has its own entry in the glossary:

Striations are a cue, not a report. They tell you which storm to watch and where to stand. Nothing in this section is reportable on its own.

Inflow bandsA band of low cloud running along the low-level wind and moving toward a storm, marking the air being drawn in. Bands curved as though turning cyclonically may mean a mesocyclone., and the one warning that matters

Inflow bands are ragged bands of cloud feeding into a storm from low levels, marking where the air being ingested comes from. Most of the time they say only that the storm is being fed. The NWS singles out one case:

That sentence is doing something precise. It says curvature may indicate a mesocyclone, which is the only sanctioned route from something you can see to the word lesson 1 told you not to use. Even here it is an implication, not an observation.

Beaver tailSpotter slang for a broad, flat inflow band attached to the updraft base, so it sits higher than a wall cloud. Frequently misreported as a funnel when seen end-on from a distance. is not tail cloudA horizontal cloud reaching from the rain area toward the wall cloud, at about wall-cloud height, with its material moving toward the wall cloud.

These two get swapped constantly, and the difference is where the feature attaches and how high its base is.

Where the rain sits decides what you can see

Module 3 covered the three supercell archetypes. This is what each one costs you when the thing you are looking for is rotation.

LP supercell

Little precipitation, so the updraft is naked. Striations, the base and any lowering are all visible from a long way off. The easiest storm to read and the least common.

Classic supercell

The textbook. Precipitation on the forward flank, updraft base clear on the rear. This is the storm every training photograph is of, and the reason Plains-trained spotters struggle elsewhere.

HP supercell

Heavy precipitation wrapping around the circulation itself. The rotation can be entirely inside the rain. Common anywhere humid, and the reason lesson 8 exists.