Reading a supercell diagram: exercises and answers

Prepare a worksheet, not a diagnosis

This exercise uses the idealized diagram and caption in the NWS guide linked below. Open it beside this page and prepare four fields on paper: observer position, viewing direction, described feature and missing information. The aim is to check a reading, not classify a storm outside your window or describe today’s weather. [s6]

First question: must every drawn feature appear in a real photograph? No. The source distinguishes the diagram from the variety of real storms; details may be absent or hidden. Write “idealized diagram” on the sheet rather than turning the drawing into a checklist of mandatory conditions. [s6]

Does image-right mean east?

In the source example, the observer is west of the storm and looks northeast. The flanking line extends south yet appears on the right of the image. Fill the first fields with “west”, “northeast” and “flanking line extending south”: geographic directions are different from screen positions. [s6]

Hypothetical task: imagine the same cropped picture without its caption, location or orientation. Can you fill those fields from its right-hand side alone? The exercise answer is “insufficient information”. Do not invent missing compass directions by borrowing them from another diagram; identify the references you actually have. [s6]

Is an unseen feature absent?

Second hypothetical task: the crop does not show a flanking line. Choose between “I cannot see it in this image” and “this storm cannot be a supercell”. The first describes the available material. The second exceeds what the diagram supports because the source allows for missing or hidden features. [s6]

Rotation of the updraft remains the defining criterion, not cloud size. If the worksheet contains no information about that criterion, record the limitation. “Not documented in this exercise” neither confirms nor rules out a real supercell. [s6]

Check the conclusion before keeping it

Final question: does a “supercell” label make a tornado certain? No: that classification does not demonstrate a tornado. Keep storm type separate from tornado presence in your answer; do not add a local forecast or infer a probability from the appearance of the drawing. [s6]

Read the completed sheet: have you separated compass direction from image side, visibility from absence, and classification from a demonstrated phenomenon? The exercise is complete when every answer identifies its evidence and what remains unknown. Repeat it with other educational material if useful, but read its own caption: this example’s geographic answers are not universal. [s6]

Sources consulted

1. The Supercell Pt. 1 — Source: NOAA / National Weather Service