again assumes that RSMC and NMHS capacities are sufficient to fully exploit improved access to global NWP, which, as discussed in Section 1.4, is generally not the case in LICs.

The influence of global forecasting products can be estimated by evaluating historical forecast accuracy, as the increase in accuracy in the last decades was largely due to the utilization of global forecasting products. At the time of establishment in the mid to late 1970s, global NWP was limited by computing power and availability/access to global observations, as well as scientific understanding of key processes involved such as cloud physics, air-sea interaction, energy transfers or turbulence. It is therefore assumed that at the time of launch, global NWP was not markedly superior to traditional forecasting approaches, at least in terms of accuracy, skill and resolution.

Quantification of increases in forecasting quality were therefore estimated considering changes in forecasting quality of ECMWF operations since 1980, published by the WMO (Simmons 2011). The data from 1980 is treated as a proxy of forecasting quality without global NWP, with an increase in ECMWF forecasting quality from 1980 to 2010 of 15 to 35 percent (depending on duration of forecast and hemisphere being forecasted). Other historical records of forecasting performance lead to similar results (e.g. NOAA 2007 and Met Office 2011).

It must however be considered that modern weather forecasting for time periods longer than 24 hours is virtually impossible without any global forecasting products, at least in the high latitudes (extratropics). Therefore, the estimation of between 15 and 35 percent improvement in overall forecasting quality has to be seen as a conservative assumption for example in North America and Europe. However as most LICs are located in the tropics, where multi-day forecasts can be skillful even without NWP, we assume that the provision of the full suite of global forecasting products would increase forecasting quality in LICs by 15 to 35 percent. Improvements in forecasts in LICs over 4-5 days are likely almost fully due to global NWP.

This increase in forecasting quality subsequently leads to increased benefits of weather and climate forecasting. Assuming that any increase in forecasting quality leads to a linear increase in benefits, the results of our benefit analysis for LICs are shown in Table 3.3.

**_Table 3.3_** _: Potential annual socioeconomic benefits of LICs due to access to global forecasting services, in 2014 values._

|**Annual benefits**|**Full forecasting improvement**|**Improvement due toglobal NWP access**|
|---|---|---|
|Minimum range|US$ 176 million|US$26.5 – 61.8 million|
|Likelyrange|US$ 1387.6 million|US$208.1 – 485.7 million|

Although standard practice in hydrometeorological socioeconomic benefit assessment, the assumption of a linear dependence on forecasting “quality” (generically describing accuracy, skill, etc.) does not consider a possibly non-linear translation from better forecast accuracy into improved decision-making. For example, a 15% increase in accuracy from 50% to 65% as compared to 84% to 99% would likely produce differing increases in benefits, as user perceptions of a generally “unreliable forecast” would not diminish for the former, while realizing near 100% accuracy for the latter would be more likely to trigger productive actions.

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