| GTG Performance statistics
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|Graphical Turbulence Guidance (GTG)
This page shows statistical performance of GTG for the past 12 months and is updated quarterly. Two types of plots are included: 1) a discrimination plot that measures the trade-offs between correctly classifying positive pilot reports of turbulence versus mis-classifying pilot reports of "negative turbulence;" 2) an airspace coverage plot that measures the trade-offs between correctly classifying positive pilot reports of turbulence versus the amount of airspace impacted by the forecasts. The skill index (SI) is related to the area under the curve for the discrimination plot and ranges from 0 to 100. The forecasts have positive skill if SI is greater than 50; larger values of SI indicate greater skill. Note that airspace is defined as the total volume, from 20,000 to 42,000 ft, covered by a Yes GTG forecast. GTG forecasts are issued at 1200, 1500, 1800, and 2100 UTC; forecasts with lead times of 3, 6, 9, and 12 hours and valid time between 1500 and 0000 UTC are included in the analyses.
In both types of plots, lines located closer to the upper-left corner represent better forecasts because better forecasts capture a larger proportion of the positive turbulence reports while simultaneously covering a smaller proportion of airspace and making fewer mis-diagnoses of the "negative turbulence" reports. The graphics below show the overall annual performance statistics, followed by statistics for each of the four seasons. Additional details on the statistical procedures used to create these graphics are available.
Autumn (Oct-Dec) performance statistics
Winter (Jan-Mar) performance statistics
Spring (Apr-Jun) performance statistics
Summer (Jul-Sep) performance statistics