Why can turbulence intensity look extreme when mean wind speed is very low?

The short answer

Turbulence intensity is a ratio of wind-speed standard deviation to mean speed over a defined interval. When the mean is very small, the ratio can become large even for modest absolute variation. That makes low-speed values important to interpret carefully, rather than treating every large percentage as the same physical condition.

Inspect both quantities behind the ratio

Review the mean speed, standard deviation, sampling method and sensor limitations for the interval. A single ratio hides the absolute fluctuation level and can be unstable when its denominator approaches zero. Confirm that missing codes or invalid values did not enter either statistic.

Do not replace the problematic denominator with an arbitrary convenient number and call the result measured turbulence. If the interval is unsuitable for the intended calculation, flag it under an explicit rule.

Compare conditions on a consistent basis

Group or condition results using a documented mean-speed range where appropriate to the assessment. Keep valid coverage and the number of observations visible. A comparison dominated by calm intervals may answer a different question from one focused on normal turbine operation.

Preserve absolute variability and direction information where relevant. A low-speed ratio alone cannot identify the obstacle, weather mechanism or sensor issue responsible for the record.

Avoid both overreaction and dismissal

A large low-speed ratio does not automatically establish unacceptable turbine loading, but low energy contribution does not make every disturbed-flow issue irrelevant. Use the equipment requirements and an appropriate site assessment to determine what evidence matters.

The report should explain the ratio's definition, low-speed treatment and resulting limitations. This allows the buyer to understand why a dramatic percentage may require context while keeping product-specific suitability, safe operating limits and mechanical assessment tied to actual engineering evidence.