Details:

Personal Author:
Brown, B. G. ; Mahoney, J. L. ; Bullock, R. ; Henderson, J. ; Fowler, T. L.
Brown, B. G. ; Mahoney, J. L. ; Bullock, R. ; Henderson, J. ; Fowler, T. L. Less -
Corporate Authors:
Forecast Systems Laboratory (U.S.)
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research)
Description:
This report summarizes basic results of an intercomparison of the capabilities 14 clear-air turbulence (CAT) forecasting algorithms to predict the locations of CAT. Some of these algorithms that have been available for many years, and some are under development. The algorithm forecasts are based on output of the Rapid Update Cycle (RUC-2) numerical weather prediction model for the period 21 December 1998 to 31 March 1999. Forecasts issued at 1200, 1500, and 1800 UTC, with 3-, 6-, and 9-hr lead times were included in the study. The evaluation also includes turbulence AIRMETs, the operational turbulence forecast product that is issued by the NWS Aviation Weather Center (AWC), and is limited to the continental United States and to altitudes above 20,000 ft. The forecasts were verified using Yes and No turbulence observations from pilot reports (PEREPs), as well as No observations based on automated vertical accelerometer (AVAR) data that were obtained from a number of aircraft. The algorithms were evaluated as Yes/No turbulence forecasts by applying a threshold to convert the output of each algorithm to a Yes or No value. A variety of thresholds were applied to each algorithm. The verification analyses were primarily based on the algorithms’ ability to discriminate between Yes and No observations, as well as the extent of their coverage. The study comprised two components. First, the algorithms were evaluated in near-realtime by the Real-Time Verification System (RTVS) of the NOAA Forecast Systems Laboratory (FSL), with results displayed on the World Wide Web (http://wwwad.fsl.noaa.gov/afra/rtvs/RTVS-proiect des.html). Second, the verification results were reevaluated in depth in post-analysis, using a post-analysis verification system at the National Center for Atmospheric Research (NCAR), with additional thresholds applied to each algorithm to provide a thorough depiction of algorithm quality. Results of the intercomparison suggest that some algorithms perform somewhat better than others. In particular, these algorithms have somewhat larger values of the True Skill Statistic for comparable thresholds, and they have a slightly larger overall discrimination skill statistic. However, the best algorithms have very similar performance characteristics. In some (but not all) cases the algorithm performance is slightly better than the performance of the AIRMETs. Results of the study also suggest that further algorithm development is needed before newer algorithms will show large improvements over some of the older algorithms. Moreover, algorithms like Integrated Turbulence Forecasting Algorithm (ITFA) may benefit by not including some algorithms that have relatively little forecasting skill. Further analyses will incorporate additional data and more complex analyses. In addition, appropriate methods will be developed to assign confidence intervals to the verification statistics, in order to evaluate the significance of differences between various statistics.
Keywords:
[+]
Clean Air Turbulence Numerical Weather Forecasting
Series:
NOAA technical memorandum OAR FSL ; 25
Document Type:
Technical Memorandum
License:
https://creativecommons.org/publicdomain/zero/1.0/
Rights Information:
CC0 Public Domain
Compliance:
Library
Main Document Checksum:
[+]
urn:sha256:4f5364ae245791c1c72d9ba291ee9d386e8ee0cfcb05510b927b25c02e346aa8
Download URL:
https://repository.library.noaa.gov/view/noaa/32812/noaa_32812_DS1.pdf
File Type:

Supporting Files

• No Additional Files

More +