Abstract:The characteristics of TCs and forecast difficulties over Northwestern Pacific in 2018 were analyzed by using the best-track data of CMA (1949-2018), CMA operational TC forecasting data of 2018, ECMWF forecast products and NCEP RTG_SST (real-time global sea surface temperature, 0.083°×0.083°) data. The results showed that the total TC genesis number was much more in 2018 than climate average and the TC generating location was more eastward, but the TCs in South China Sea were much more active. The TC genesis time concentrate in summer and the TC genesis number in summer was much more than climate average. The TC genesis clusters and coexisting multiple TCs were frequently seen. The annual lifetime of TCs was longer and the accumulative cyclone energy was higher. However, the overall TC intensity was much weaker, and the proportion of weaker TCs was abnormally higher. The number and frequency of land falling TC were much higher, and the landing TC locations were northward, but the landfalling TC intensity was abnormally weaker. The track forecast errors of CMA this year decreased compared with those of 2017 for all forecast leading time, with the value of 72, 124, 179, 262 and 388 km for 24, 48, 72, 96 and 120 h lead time. Especially, the track errors decreased obviously for long lead-time. The intensity errors respectively were 3.7, 5.1, 5.5, 6.6 and 7.1 m·s-1 for 24, 48, 72, 96 and 120 h lead time. The track forecast difficulties were mainly caused by complex interaction between binary typhoons or among multiple TCs as well as the large uncertainty caused by the saddle circulation. Meanwhile, the uncertainty of intensity forecast of TCs near off-shore and the complex moisture transport among multiple TCs are the main causes for the difficulties of TC intensity forecasting. The forecast problems would be solved effectively if there were more observations, in-depth mechanism studies and more effective forecasting techniques.