Verifying forecast accuracy is a critical step in providing valuable forecast products for use by the aviation community. Marilyn Wolfson of the Massachusetts Institute of Technology Lincoln Laboratory framed her comments about verification schemes around the question “How will we know when we’re done?” To answer this question, she started by defining the intended use of weather forecasts from an aviation perspective, which is to improve flight planning and thus maintain schedule integrity. Weather forecasts are used to predict the expected capacities in various en-route sectors of airspace as a function of space and time; route availability, including initial routes, alternate routes, miles in trail spacing, blockages, and flow-constrained areas; and terminal impacts, including the availability of alternate airports for landing en-route planes.

Based on these needs of the aviation community, Dr. Wolfson noted that her thoughts on verification are based on postulating the following characteristics for improved 2- to 6-hour forecasts. First, she opined that there is general consensus that probabilistic forecasts are needed and that they should be designed for utility and value to the ultimate user. In addition, the forecasts need a high level of specificity in space and time, particularly in terms of resolving convection. Lastly, forecasts need to be generated automatically, with standardized outputs, low latency, and high reliability. Indeed, providing a continuum of forecasts with different lead times—for example, in granularities of 15 or 30 minutes—would be more valuable to those making flight planning decisions than the currently provided 2-, 4-, and 6-hour products. An automated system may help eliminate bias or equity issues associated with forecasts provided by individual entities. Even with an automated system, forecasters may need to play a role in updating, reviewing, and editing the automated output.

Dr. Wolfson identified several forecast characteristics of particular importance for anticipating how convective weather will impact the national airspace. These characteristics include:

• Spatial coverage and timing: These can be considered together because forecasts may often trade off accuracy in space and time. Verifications of the temporal and spatial characteristics of convection will likely need to include a probabilistic tolerance for errors that increases as the forecast extends farther into the future.

• Strength and height of the storm: Many en-route flights avoid storms by flying over them, rather than around them. Accurate vertical information