So, this is my first Storm Calc.
There are a large number of storm feats in the Witcher verse, so I feel like we can't really call any and all of them outliers anymore. I can name four instances where storms are formed by characters in the Witcher; Eredin causes one in W1, which I will be calcing, this mage a small lightning storm, The Djin in W3 creating a storm, and The Wild Hunt causes a storm when they are teleported to Geralt and co. in W3. Carthirnir also makes a blizzard in W3, but we don't see him make it, we just see him finishing the spell, and the storm is already there.
So, without further aideu:
Eredin Causes a Storm[]
The Feat: https://youtu.be/y7v8Y7K0FOM?t=385
Storm forms from 6:29 to 6:34
We can't see up to the horizon due to the debris, so I will assume the storm is only covering the platform they are standing on.
Average male Polish height: 178.7 cm.
178.7 cm = 38 px
Mound he's standing on: 178.7 * 213 / 38 = 1001.66 cm
Second Image: 1001.66 cm = 37 px.
Diameter of the Structure: 1001.66 * 302 / 37 = 8175.71 cm
Area: pi * (4087.855^2) = 52497767.82 cm squared, or 524977.68 meters squared.
(524977.68 * 13,000) * 1.003 * CAPE
I will use moderate and strong instability; the winds are moving fast enough to create a nearly opaque barrier of dust (ice?).
Low End: (524977.68 * 13,000) * 1.003 * 2500 = 1.711296e+13 J, or 4.09kT of TNT. Small Town level+
High End: (524977.68 * 13,000) * 1.003 * 4000 = 2.7380736e+13 J, or 6.5 kT of TNT. Town level
This scales to Geralt, Strong Mages, and everyone who scales between.