Abstract:MM5 through using various cumulus parameterization schemes and various leading times from both deterministic and ensemble forecast points of view. The results show that the simulated tracks with 48h leading tim e at 1200 UTC on 7 Aug. 2005 with various cumulus parameterization schemes all t urn to the northeast and consequently will not have a direct impact on Beijing. When the leading time extends to 60 and 72 hours, the simulated tracks with the predictability of the recurvature of typhoon Matsa (0509) in Bohai on August 9, 2005 was examined with Kuo and Betts Miller cumulus parameterization schemes ar e still close to the observations, while the simulated storms with Grell and Kain Fritch schemes deviate to the n orthwest of the real track and thus may affect Beijing directly. The better per formance of Kuo and Betts Miller schemes in predicting the sudden turning of Ma tsa in Bohai is also confirmed in the ensemble forecast. An uncertainty of forec ast with Kuo and Betts Miller cumulus parameterization schemes was observed to be smaller than that with Grell and KainFritch schemes. The predictability of Ma tsa sudden turning to the northeast at Bohai could be around 2 days.