Research On The Performance Of Typhoon Track Forecast In The Northwest Pacifi

Tropical cyclones(commonly known as typhoons in the western North Pacific(WNP)region)are one of the most serious natural disasters affecting human beings,and bring severe challenge to the disaster prevention and mitigation work of many countries around the world every year.The capacity of typhoon track forecast has improved considerably over the past few decades.However,the decreasing trend of typhoon track forecast error has gradually stagnated in recent years,and the debate about whether the typhoon track forecast has reached the limitation under the current observation and forecast technology has gradually heated up.In this paper,we analyze the current actuality and trend of track prediction errors in the official subjective track forecast guidance,global and regional models in the WNP,and discuss the predictability of typhoon tracks in the Northwest Pacific.In addition,based on the historical track errors of the global model,an integrated typhoon optimal weight track forecast method has been developed and verified.The main conclusions of this article are as follows:First of all,at present,the errors of typhoon track forecast from the official typhoon forecast agencies at 24,48,72,96 and 120 h are generally close to 70,130,200,220 and 290 km.However,extreme large track forecast errors still existed every year.The typhoon track forecast errors within 3 days reached their lowest values around 2015,and the performance of track forecast did not improve significantly in the following years.According to current observation techniques and model techniques,the capability of typhoon track forecast will gradually reach its limitation in the next 15 years.Secondly,the global and regional models have made no significant improvement in typhoon track forecasting since 2015.There existed some systematic biases in the track forecast results of models.Moreover,we found that the initial conditions of typhoon itself and its surrounding are the good indicators for typhoon track forecast.When the typhoon is in one or more conditions with relative strong initial intensity,large initial size and strong initial environmental steering flow,the track errors of models are relatively smaller,and vice versa.Thirdly,based on the global model historical track forecast error data,combined with different types of typhoons themself and their surrounding environmental factors,an optimal weight integrated track forecast method was established.After two years of real-time operational forecast in the 2020 and 2021 WNP typhoon seasons,the new track forecast method shows that it can effectively suppress the formation of extreme track forecast errors,which reflects it has good capability in track forecast improvement.