Following the 2010 Deepwater Horizon accident of a massive blow-out in the Gulf of Mexico, scientists from government, industry, and academia collaborated to advance oil spill modeling and share best practices in model algorithms, parameterizations, and application protocols. This synergy was greatly enhanced by research funded under the Gulf of Mexico Research Initiative (GoMRI), a 10-year enterprise that allowed unprecedented collection of observations and data products, novel experiments, and international collaborations that focused on the Gulf of Mexico, but resulted in the generation of scientific findings and tools of broader value. Operational oil spill modeling greatly benefited from research during the GoMRI decade. This paper provides a comprehensive synthesis of the related scientific advances, remaining challenges, and future outlook. Two main modeling components are discussed: Ocean circulation and oil spill models, to provide details on all attributes that contribute to the success and limitations of the integrated oil spill forecasts. These forecasts are discussed in tandem with uncertainty factors and methods to mitigate them. The paper focuses on operational aspects of oil spill modeling and forecasting, including examples of international operational center practices, observational needs, communication protocols, and promising new methodologies.

ABSTRACT> The ICS 232 Resources at Risk summary form is a key tool for the communication of resources at risk from an oil or chemical spill. Completion of the form requires consideration of environmental, archeocultural, and socio-economic resources that may be affected by a spill. This process of research, identification, prioritization, documentation, and communication of potential resources in the pathway of a spill is typically conducted within the Environmental Unit (EU) by the Resources at Risk (RAR) Technical Specialist or Environmental Unit Leader (EUL), with input from relevant stakeholders and trustees. The purpose of the form is twofold: to provide environmental information to aid assessment and decision making, for example: identifying where to conduct wildlife reconnaissance surveys, identifying resources of concern for Spill Impact Mitigation Assessment (SIMA)/ Net Environmental Benefit Analysis (NEBA), and recommending cleanup techniques and endpoints; andTo provide direct priorities for protection for response operations, such as from pre-established Geographic Response Plans (GRPs) or Geographic Response Strategies (GRSs), and other static or Geographic Informational Systems (GIS) data sources. In recent years, GRP/GRSs have become more commonplace in contingency plans, and have become more practical for response operations, to a degree that some plans include executing the GRP/GRSs as ready-made ICS 204 (work order) forms to provide direct instruction to response operations on site location, access, operational strategies, and equipment required to protect specific resources. This pre-spill information can be valuable to ensure that priority resources are protected within the short window of opportunity that is typically available at the beginning of a response; and allows quick decision-making without the need for in-depth consideration of sensitivity and resource maps. A potential downside to this convenient data, which will be explored in this paper, is that we risk relying entirely on using the GRP data to provide operational protection priorities and losing the specific data on the resources we are aiming to protect. This reduces the purpose of the form to a purely operational instruction, without the documentation of environmental data that is essential for assessment and decision making within the Environmental Unit. This paper considers the use of the ICS 232 (Resources at Risk) form, how its use has developed over the years, and how the availability of GRPs has, in some areas, shifted the use of the form to a more directly operational purpose. Recommendations are provided for ensuring that the environmental information component is not forgotten.

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