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THE FUJITA SCALE

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THE FUJITA SCALE

six categories of tornado damage — and the two different winds assigned to them

Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.

Three sizes in one archive — from a sheet on the fridge to a poster on the wall.

Standard$1.50

Payment and email are handled by Paddle. The download link arrives by email — no account, no password.

Formats
A4 · A3 · A2
What you get
Print-ready PDFs, one per size, with every letterform converted to outlines — nothing to install, nothing to shift.
Subject
science · comparison · everyone · study

The upper bar is the Fujita scale of 1971, the lower one the EF scale in force; both are brought to a three-second gust, so the bands can be compared. In the table each scale appears in the frame its own source records it in; the kilometres are converted from miles and rounded.

THE TWO SCALES AGREE AT EXACTLY ONE POINT

The new scale was derived from the old one by a single straight line: y = 0.6246x + 36.393, where x is the Fujita wind and y the EF wind for the same damage (both three-second gusts, mph). That line meets the identity exactly once, at 97 mph — the one wind speed both scales describe the same way.

Below that mark the old scale understated the wind: category zero used to begin at 45 and now begins at 65. Above it the old scale overstated, and increasingly so: category five used to begin at 262 and now begins at 200. The report states the reason plainly: Minor et al. (1977) and Phan and Simiu confirmed that the fourth and fifth categories overestimated the wind — a well-built house does not need 260 mph to be levelled and its debris carried away.

The category numbers were kept deliberately so that the historical tornado record survives: an F3 becomes an EF3, and only the wind ranges change. Category five has no upper bound, and that too is a decision rather than an oversight: so that the worst is not assumed of every strong tornado.

On the sheet

  • The upper bar is the Fujita scale of 1971, the lower one the EF scale in force; both are brought to a three-second gust, so the bands can be compared. In the table each scale appears in the frame its own source records it in; the kilometres are converted from miles and rounded.
  • Colour carries meaning, but meaning never rests on colour alone — the sheet reads in black and white.
  • Nothing about how it was made: the sheet carries only what the reader needs.

Printing

  • Three sizes in the archive: A4 — 210×297 mm, A3 — 297×420 mm, A2 — 420×594 mm.
  • All text is converted to outlines. No fonts to install, and nothing shifts on another machine.
  • White background and sparing fills — it prints on a home printer without draining the cartridge.
  • Margins of at least 10 mm: a home printer cannot print to the edge.
  • No stroke thinner than 0.3 mm, so nothing disappears in print.

Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 9 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.

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