Forestry harvesting contractors and foresters: the wind call, at your height

Daily in winter, you make the call to stand down felling, harvesting, or road haulage. This decision is based on whether gusts threaten the stability of standing or windblown timber, or create hang-ups. A wrong call can mean idle machines and crews, and re-planned haulage. The cost of a wrong call can extend to significant operational delays and financial penalties, particularly when dealing with tight schedules and specialised equipment.

Windblown timber is tension-loaded and presents one of the highest-risk felling situations. Guidance from the HSA and Teagasc IFSG highlights these dangers, emphasising the need for careful assessment of wind conditions. The decision to stand down is yours, guided by your site risk assessment, Coillte contractor rules, or the manual felling code, not by any instrument. These documents provide the framework for your operational limits.

Your call determines if work proceeds. The instrument provides information to help you make that call, showing you the wind conditions at your working height. It does not approve or certify any action, but offers a clear view of the forecast wind to inform your judgement. This allows you to proactively manage risks and protect your crew and assets from adverse weather conditions.

Your work requires knowing the gust at canopy height, not just the wind at 10 m over open ground. The instrument displays wind at 10, 80, 120, and 180 m, then interpolates this to your specific working height. For forestry, this is typically set at 20 m, which is badged as 'gust at canopy height'. Heights below 10 m are extrapolated below the lowest model level and badged as such, indicating less certainty.

Gusts are presented alongside the mean wind speed. This distinction is important for felling and harvesting operations, where sudden increases in wind speed can pose immediate risks to personnel and equipment. The instrument focuses on providing this specific gust information at the relevant height for your operations, allowing you to assess the immediate threat.

Your limit for standing down is set by your own documents, such as your site risk assessment or the manual felling code. The instrument allows you to input this limit, giving you a direct comparison between the forecast and your operational threshold. This helps you assess the immediate conditions for your work and make informed decisions about continuing or pausing operations.

The instrument shows the P(above your limit) by the hour, which is the fraction of ensemble members that exceed your set limit. This is computed from ensemble members at 10, 80, 100, and 120 m. It is not a calibrated certainty, but an indication of how many model runs predict winds above your threshold. This gives you a probabilistic view of potential exceedances.

The Agreement Spine shows where weather models agree and where they do not. This helps you understand the confidence in the forecast. If the models largely agree, the forecast is more likely to be stable. If they disagree, there is more uncertainty, suggesting a need for increased vigilance or a more cautious approach to operations.

For example, if the P(above your limit) is 20 per cent, you might proceed with caution, monitoring conditions closely. If it is 50 per cent, you might consider delaying or re-scoping the work, as there is a significant chance of exceeding your limit. At 80 per cent, a stand-down is likely, as a significant majority of models indicate conditions above your limit. These percentages are illustrative; your response depends on your own assessment of risk and the cost of a wrong call for your specific operation.

It is an example of a day using the instrument for forestry work. At 06:00, you check the forecast for the day. The P(above your limit) at 20 m for 10:00 to 14:00 is 20 per cent, with gusts of 12 metres per second (m/s). This initial forecast suggests conditions are likely to be within your operational limits.

By 07:00, you decide the crew can start, but you will monitor the forecast throughout the morning. At 09:00, you check again. The P(above your limit) for 10:00 to 14:00 has risen to 50 per cent, with gusts now forecast at 15 m/s. The Agreement Spine shows less model agreement for the afternoon, indicating increased uncertainty.

At 09:30, recognising the elevated risk, you call the crew. You advise them to complete any work on stable timber and prepare to stand down by 11:00. By 10:30, the P(above your limit) for 11:00 to 15:00 is 80 per cent, with gusts at 18 m/s. Given this high probability of exceeding your limit, you make the call to stand down felling operations for the rest of the day.

By 11:00, the crew secures equipment and leaves the site. You note the decision in the instrument's record page for the site file, documenting the conditions and the action taken.

Your operational limit for wind is a critical factor in your daily decision-making. This limit is not set by the instrument, but comes directly from your own documents, such as your site risk assessment, Coillte contractor rules, or the manual felling code. It is the threshold at which you decide to stand down felling, harvesting, or road haulage due to gust conditions, ensuring the well-being of your crew and the protection of your machinery.

The instrument allows you to input this specific limit, which is then used to calculate the P(above your limit) by the hour. The instrument's preset height for forestry operations is 20 m, which aligns with canopy height. This ensures that the forecasts are relevant to the conditions you face in the forest, providing data at the height most critical for your work.

It is important to review and update your limit as your site conditions or operational guidelines change. The instrument uses the limit you provide to give you a clear, objective measure against which to assess the forecast wind conditions. This supports your judgement in making the call, grounding your decisions in your established operational parameters.

The instrument provides a dated record page of what was forecast, what was observed, the limit you used, and the call you made. This record is important for your site file and can be reviewed if questions arise about operational decisions. It offers a transparent account of the conditions and your response to them.

Organisations like Coillte, the HSA, and Teagasc IFSG often require documentation of site operational decisions. Having a clear record of your wind-related stand-down calls, based on objective forecast data and your set limits, can support your operational standards and demonstrate adherence to established protocols. This documentation can be crucial for internal audits or external inquiries.

For you, the harvesting contractor or forest manager, this record serves as proof that you acted on wind conditions to protect your crew and equipment. It shows that decisions to stand down were made based on available information and your established operational procedures. This can be useful for internal reviews or in discussions with clients and regulators, providing evidence of responsible management.

Ireland's forestry sector faces specific challenges due to its Atlantic exposure, particularly during the storm season from October to March. This period often brings strong winds that necessitate daily decisions on felling and harvesting operations. Met Éireann provides national forecasts, but specific, localised wind data at canopy height is often needed for forestry work, where conditions can vary significantly from open ground.

Windblown timber, often a result of these storms, presents ongoing high-risk felling conditions. The need for precise gust forecasts at working height is heightened when dealing with such timber, as unexpected wind shifts can increase the danger. The instrument provides forecasts specific to your operational height, which can be critical in these situations, helping to mitigate risks associated with unstable timber.

The general Irish context, with its regular exposure to severe weather, underscores the need for robust decision-making tools. While the instrument does not provide local observations, it uses modelled data to give you a detailed forecast relevant to your site's conditions, helping you prepare for the variable weather. This allows for more informed planning and operational adjustments in a challenging environment.