It would be helpful to provide a more explicit link between seasonal to interannual climate variability and climate change, since there is so much emphasis on climate change in the rest of the document. Some relevant points to consider:

  • The value of seasonal to interannual decision-support systems to climate change adaptation. In theory, awareness and preparation for seasonal to interannual variability can contribute to adaptation to climate change. However, it would be useful to specify the decisions that seasonal to interannual forecasting does not address that require longer time-scale information and to be clearer about the relevant time scales: 10 years? 50 years?

  • Expectations of skill may be erroneous, that is, for low-frequency variations predicted in year-to-year operations. While seasonal to interannual predictions show greater skill for temperature variability than precipitation, they have not done a good job at capturing the widespread increases in above-normal temperatures over the United States. Although precipitation would appear to be more difficult to predict, many seasonal to interannual predictions did a reasonable job capturing the multiyear drought from 1998 to 2001 (prediction review of the Predictability, Prediction & Applications Interface Panel, U.S. CLIVAR).

  • There are important similarities and differences in the current approaches to predictions versus projections (e.g., no greenhouse gas changes in seasonal to interannual predictions).

Shorten the discussion of forecast skill. This discussion currently takes up two-thirds of the chapter and has a lot of repetition that could be eliminated with tighter organization.

  • Section 1.4.1.1, Some Basic Concepts Regarding Forecast Skill, could be dropped. This is 4 pages long, and much of what it says is repeated later. This could potentially be replaced by a short section on the metrics of forecast skill that describes correlation and perhaps something probabilistic, as well as the differences between real and potential predictability. Those tangents later detract from the discussion.

  • Information in section 1.4.4 should be absorbed into 1.4.3 and not be a separate section.

  • There is a lot of repeated information between 1.4.2, Sources of Hydrologic Forecast Skill, and 1.4.5.1, Skill of Seasonal Water-Supply Forecasts. Perhaps it would be more economical to not separate “sources of skill” from “skill” but have those be a single section—one section for climate and one for hydrology.

  • The section Skill of Climate Forecast-Driven Hydrologic Forecasts also has much redundancy. Skill of forecasts is the same concept, whether they are statistical or dynamically driven. If these really need to be broken out into separate subsections, at least have one follow the other.

  • The section on skill of long-term climate projections has little on skill assessment, so the section could be shortened quite a bit.

  • Why does climate come after the hydrology in section 1.4? It would seem to make more sense for climate to come first.



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