The EF scale

A Vortex Dread tornado never gets handed a rating up front. The rating is read off whatever wind it happens to be carrying at that exact moment, the same way a real damage survey reads a building rather than a forecaster's guess. Six floors do the actual work, 29, 38, 50, 61, 75 and 90 metres per second of three-second gust, and every one of them comes with a mature core radius built from a single rule: coreRadiusAtEf0 × (peak wind / 29) ^ radiusGrowthExponent. Nothing below the first floor counts as a tornado worth rating at all, that call belongs to whatever triggered the event in the first place. Out of the box, the formula starts from coreRadiusAtEf0 = 6.0.

The six ratings

Every rating, its wind floor and its mature core
Rating	Category	Floor	What it tears loose
EF0	Light damage	29 m/s	A 6-block core, resistance torn up to 0.35: foliage, flowers and glass go first, everything else stands.
EF1	Moderate damage	38 m/s	A 9-block core, up to 0.79 resistance: bare dirt and sand start lifting as well.
EF2	Considerable damage	50 m/s	A 14-block core, up to 1.79: gravel, clay and wool join in, the track becomes readable from a distance.
EF3	Severe damage	61 m/s	An 18-block core, up to 3.26: planks and logs give way, a wooden house empties out.
EF4	Devastating damage	75 m/s	A 25-block core, up to 6.05: stone itself starts to give.
EF5	Incredible damage	90 m/s	A 33-block core, up to 10.5: only obsidian and bedrock are left standing.

These numbers are only floors. EfScale.fromWind reads the actual wind at that instant, which can climb anywhere up to the next floor before the category changes. EF5 has no ceiling in reality, and none here either: its band borrows the width of the one below it, which pushes the theoretical worst case to near 110 metres per second.

Everything gives way eventually, except two blocks. Past a resistance of 900, no wind pulls a block loose, whatever its strength: obsidian, sitting at 1200, gets covered twice over, and bedrock is not even part of the conversation.

How the odds are stacked

A freshly spawned tornado does not draw its strength from a flat spread across the six ratings, it follows a distribution modeled on the real thing, where the weak cases dominate by a wide margin. One setting tips it, ratingBias: push it positive and violent tornadoes get more common, push it negative and the sky stays stuck with weak ones, leave it at zero and the breakdown below applies as written. Set it to 1, for instance, and the chance of topping out at EF0 falls to somewhere near 25 percent, down from 60 percent by default, without ever making an outcome impossible.

EF0: six tornadoes out of ten never get past this floor, the most ordinary rating in the game.
EF1: 28.0 percent.
EF2: 8.0 percent.
EF3: 3.0 percent.
EF4: 0.8 percent, already rare.
EF5: 0.2 percent, a little under one in five hundred, the only rating with no wind ceiling of its own.

What can be moved

The four settings that belong to this page
Option	What it moves	Default
ratingBias	Tips the breakdown above toward weak or violent, in steps of EF.	0.0
coreRadiusAtEf0	The first of the six cores in the table above, the one the other five scale from.	6.0
radiusGrowthExponent	The power in the formula: push it higher and the gap between EF0 and EF5 widens further.	1.5
resistanceScale	Multiplies the resistance every block has to absorb before it gives. Drop it under 1 and even stone eventually holds.	1.0

The effect of the exponent

The chart lines up mature core width against peak gust for two different settings of radiusGrowthExponent: the faster the curve climbs, the more obvious the gap between a weak tornado and a violent one becomes at a glance.