Marine construction and dredging contractors: the wind call, at your height

As a Marine Operations Manager, you decide daily and weekly whether to mobilise a crane barge or a dredger, and how to plan weather windows for these operations. This decision directly impacts project timelines and costs, as vessel day rates can be substantial.

Your call is critical because a wrong decision can lead to significant financial penalties, particularly related to weather standby clauses in contracts. Beyond costs, there are operational risks, especially when conducting lifts from barges in unsuitable conditions.

The limits for these operations are typically set by the vessel specifications and the lift plan for each specific task. These documents define the maximum mean wind speed, often in knots, and significant height (Hs) that permit efficient work. It is your responsibility to interpret these limits against the forecast.

Each decision you make requires a clear understanding of the wind conditions at your working height. The instrument helps by providing wind data specifically interpolated to your crane or dredger height, allowing you to align your operational limits with precise meteorological information.

For marine construction and dredging, your working height is often around 20 metres, which is the typical height of a crane boom or the effective height for assessing conditions for a dredger. Wind conditions at this specific height can differ significantly from those measured at standard meteorological stations, which are often at 10 metres, or from general area forecasts.

The instrument provides wind data at 10, 80, 120, and 180 metres. It then interpolates this data to your exact working height, for example, 20 metres. This ensures you are looking at the wind conditions relevant to your equipment, not just a general surface wind.

Your operational limits are usually defined by mean wind speed, often in knots. However, gusts are also a critical factor, as sudden increases in wind speed can pose risks to stability and lifting operations. The instrument displays gusts alongside the mean wind, allowing you to consider both when making your call.

The limit itself is not set by any external body, but by your vessel specifications and the lift plan you are working under. You input this limit into the instrument to tailor the forecasts to your specific operational parameters.

The instrument presents the odds of wind exceeding your specified limit by the hour, computed from ensemble members. This is the fraction of ensemble members that predict wind above your limit in that hour. It helps you quantify the risk of exceeding your operational thresholds.

When the odds are, for example, around 20 per cent (one in five ensemble members), you might proceed with caution, perhaps preparing for potential delays or having contingency plans in place. If the odds rise to 50 per cent (half the ensemble members), this indicates a significant risk, and you would likely delay or reschedule non-critical operations.

At 80 per cent odds (four out of five ensemble members), it is a strong signal that conditions will exceed your limit, and you would typically postpone operations or secure equipment. These percentages are examples, and your response will depend on your specific project's risk tolerance and the cost of a wrong call.

The Agreement Spine feature shows where different weather models agree or disagree on the forecast. High agreement across models, especially when predicting adverse conditions, strengthens the confidence in the forecast, even if the odds of exceeding your limit are low. Conversely, low agreement suggests higher uncertainty, which you might factor into your decision-making by adding a buffer to your operational limits.

It is an example for a crane barge operation with a 20-knot mean wind limit at 20 metres.

6:00: You check the instrument. The morning brief shows a 10 per cent chance of exceeding your 20-knot limit at 20 metres for the next 48 hours. The Agreement Spine indicates high model consensus for light winds. You decide to mobilise the crane barge and proceed with planned operations.

10:00: Work is underway. You check the forecast again. The odds remain low, and the wind is currently 12 knots at 20 metres, well within your limit. Operations continue as planned.

14:00: A quick check shows the odds have risen to 30 per cent for a four-hour period starting at 18:00, with some model disagreement. You instruct the team to monitor conditions closely and prepare for potential temporary suspension of lifting operations.

17:00: The wind is now 18 knots, and the odds of exceeding 20 knots from 18:00 to 22:00 are 60 per cent. You make the call to suspend lifting operations at 17:30 and secure the crane. Dredging operations, with a higher wind tolerance, continue.

22:00: Wind has dropped to 15 knots. The odds for the next morning are back to 10 per cent. You plan to resume lifting operations at first light, having avoided working in conditions that would have exceeded your limit.

Your operational limit for mean wind speed is a critical input for the instrument. This limit is not a general guideline but a specific threshold derived from your project's documentation, such as the vessel's operational manual or the lift plan for a particular task.

For marine construction and dredging, this limit is often expressed in knots for mean wind at a specified height, typically around 20 metres. You will find this figure in your own engineering documents or risk assessments. It is essential that you accurately input this value into the instrument.

The instrument comes with a preset for 'crane' operations at 20 metres, with 'mean wind (knots)' as the primary metric. You can adjust this height and metric if your specific operation requires different parameters, ensuring the instrument reflects your exact working conditions.

By setting your precise limit, the instrument can then compute the probability of exceeding this specific threshold, providing you with tailored risk information. This helps you adhere strictly to your operational parameters and avoid any breaches of contract or project protocols.

The instrument maintains a dated record page of what was forecast, what was observed, the limit you used, and the call you made. This record is essential for marine construction and dredging operations, particularly when dealing with standby claims and project audits.

For example, if you face a weather standby claim, this record provides objective evidence of the meteorological conditions that led to your decision to suspend or delay operations. It documents that your call was based on the best available forecast at the time, aligned with your specified operational limits.

This audit trail is also valuable for internal reviews of operational efficiency and for demonstrating due diligence in adhering to project specifications and project protocols. It removes ambiguity about past weather conditions and decisions, helping to resolve disputes or justify project extensions.

Maintaining a clear record allows you to review past forecasts against actual conditions, helping you to refine your decision-making over time. It serves as a factual basis for discussions with clients, insurers, or regulatory bodies regarding weather-related delays or incidents.

Ireland's marine environment, particularly along its Atlantic coast, experiences significant wind variability, which directly impacts marine construction and dredging. The storm season typically runs from October to March, bringing higher wind speeds and more frequent severe weather events.

Operations in locations such as Dublin Bay, Cork Harbour, or various west-coast harbours must account for these conditions. While the working season generally spans from April to September, even during these months, sudden weather changes can occur, necessitating careful planning.

Met Éireann, as the national forecaster, provides general meteorological information, but your operations require precise wind data at your specific working height. The instrument addresses this need by interpolating wind forecasts to the exact height of your crane barge or dredger.

Understanding the probability of wind exceeding your operational limits is particularly important in a climate where weather windows can be short and unpredictable. This allows you to plan mobilisations and operations to maximise efficiency while adhering to contractual and project requirements.