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Tropical cyclone track analog ensemble forecasting in the extended Australian basin: NWP combinations
Author(s) -
Langmack Hans,
Fraedrich Klaus,
Sielmann Frank
Publication year - 2012
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.1915
Subject(s) - meteorology , tropical cyclone , track (disk drive) , tropical cyclone forecast model , environmental science , climatology , numerical weather prediction , ensemble forecasting , computer science , geography , geology , operating system
Ensemble‐Weighted Analogs (EWA) are introduced as an empirical forecast model for tropical cyclone (TC) tracks in the Australian basin extending to the Indian Ocean. The input requires only the 6 h positions of the preceding 24 hours to estimate the actual TC's future locations (up to 48 hours ahead) using optimally weighted ensemble members (analogs) from sections of historic cyclone tracks. They are determined as nearest neighbours of the actual track positions. After model calibration, independent forecasts are evaluated (2001–2007). The forecast analysis shows an error of about 140 km (for the 24 h prediction), which is better than the CLIPER reference forecast (161 km) and comparable to a numerical weather‐prediction model (NWP of the UK Met Office). Intensity estimates and the forecast error‐spread relation are discussed. Error‐minimizing forecast combinations are also analysed: the EWA–NWP combination improves the individual 24 h NWP forecasts by about 25 km. Track cluster conditioned 24 h EWA forecasts are introduced providing probability estimates of hazardous areas. Finally, two cases of sudden track changes and their forecasts are presented with fields of position probabilities derived from the analog ensemble members and their clusters. Copyright © 2012 Royal Meteorological Society