Weather donwtime glossary
Key terms used in metocean analysis and weather-window planning for offshore operations.
A continuous period in which metocean conditions stay within the operating limits of a marine activity long enough to complete it safely. Finding and forecasting weather windows is the core of offshore operations planning.
Short for meteorological and oceanographic. Metocean data describes the wind, waves, and currents at a site — the conditions that determine whether marine work can proceed.
Whether an activity can be carried out under given metocean conditions. An activity is operable when conditions stay below its limiting criteria, such as significant wave height and wind speed.
A standard measure of sea state, roughly the average height of the highest third of waves. Hs is one of the most common limiting criteria for marine operations.
How long suitable conditions last without interruption. An operation needs a window of sufficient persistence, not just a single calm moment, to complete.
Probability levels for a duration or outcome. A P50 value is met or beaten 50% of the time; a P90 value 90% of the time. P90 is used to add weather contingency to a plan.
Time when an operation is on standby because conditions exceed its limits. Waiting on weather drives downtime and standby cost and is a key output of a weather-window analysis.
A method that runs a model many times with different inputs to map the range of possible outcomes and their probabilities. Aventis uses it to simulate a campaign against many weather sequences.
A reduction factor from the DNVGL-ST-N001 standard applied to operational limits to account for forecast uncertainty, so planned weather windows reflect forecastable conditions rather than perfect hindsight.
A reconstruction of past metocean conditions from models and observations. Hindcast time series provide the historical weather used to estimate weather-window statistics.
The time it actually takes to complete an activity or campaign once waiting on weather is included — typically reported at P50 and P90 confidence levels.
Productive time lost to conditions exceeding operating limits, equipment, or other constraints. Weather-driven downtime is quantified by waiting-on-weather analysis.