FA-71237 / Weather index computation / Member archive

Vector-mean wind and steadiness: atan2 argument order · case 02

Westerly winds are reported as southerly.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

obs are [speed, direction_from_deg]. Components u=-s*sin(d), v=-s*cos(d); average them. Return [vector speed rounded 0.01, direction the wind blows FROM in [0,360) rounded 0.1 or None if the vector speed is below 1e-9, steadiness = vector speed / scalar mean speed rounded 0.001 (0.0 if calm)]; empty input returns None.

Why this case matters

Wind roses, dispersion inputs and runway selection need vector-mean wind direction.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
mast 3	`[5.1, 92.1, 0.823]`	`[5.1, 357.9, 0.823]`	Failed

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