ISO 19901-1:2026

This document provides two broad types of requirements for the determination and use of meteorological and oceanographic (metocean) conditions for the design, construction and operation of offshore structures:

• those related to the determination of environmental conditions in general, together with the metocean parameters that are required to adequately describe them;
• those related to the characterization and use of metocean parameters for the design, the construction activities or the operation of offshore structures.

This document covers the following environmental conditions and metocean parameters:

• extreme and abnormal values of metocean parameters that recur with given return periods that are considerably longer than the design service life of the structure;
• long-term distributions of metocean parameters in the form of cumulative, conditional, marginal or joint statistics of metocean parameters;
• normal environmental conditions that are expected to occur frequently during the design service life of the structure.

Metocean parameters specified in this document are applicable to:

• the determination of actions for the design of new structures;
• the determination of actions for the assessment of existing structures;
• the site-specific assessment of mobile offshore units;
• the determination of limiting environmental conditions, weather windows, actions and action effects for pre-service and post-service situations (i.e. fabrication, transportation and installation or decommissioning and removal of a structure);
• the operation of the platform, where appropriate.

It is beyond the scope of this document to provide detailed instructions that can be followed to produce reliable estimates of extreme or abnormal conditions in all areas and in all cases.