The Forecast Research Of Strong Winds At Sea Caused By Extratropical Cyclone

First,the paper studies the strong winds' regulations and climate characteristics on the sea caused by extratropical cyclone(including Jianghuai cyclone, the East China Sea cyclone and Yellow Sea cyclone) in Zhejiang northeastern coast area.For the first time,we get interannual change and inter_monthly variation characteristics,cyclone strong wind direction and the number of days changing, which can supply climate background formation for forecasting cyclone strong winds on the sea.Second,diagnoses and analyzes two strong winds on the sea caused by developing cyclones in the April 9,2005 and June l,2006.Also there's a discussion of synoptic meteorology causes on the development of the cyclones and concludes some forecasting indicators.Through simulation of the East China Sea cyclone developing process on June 1,2006,it's possible to reveal the cyclone development of the physical mechanism after moving into the sea.The results show that the releasing of latent heat is the most important reason of cyclone development.The high-level through and warm advection provided a large-scale development environment for cyclones,which arouse mainly latent heat release through the positive vorticity advection and warm advection to maintain cyclone development.Through research of studying of 10 years of synoptic charts from January 1, 1990 to January 1,2000 and with the experience of the past cyclone forecasting, dividing cyclones into Jianghuai cyclones,the East China Sea and Yellow Sea cyclones,which is divided into a number of subtypes,analyze the weather situation 24 hours before the development of the cyclone and build up a cyclone forecasting model and lay up the foundation for strong winds forecast based on this model.Then according to the synoptic meteorology and "t" statistics analysis come to the conclusion that the strong winds of cyclones had close relation with the lower-front at 850hPa,the surface pressure gradient,high-low level wind shear,the middle-lower level temperature and dew point difference and vorticity,and 500hPa temperature and a high degree of deviation.Thus,mainly select forecasting factors from those physical factors,including 13 forecasting factors. Through BP artificial neural network and prediction factor,establish the cyclone strong winds forecast model by sample trainings.Finally,the cyclone winds forecast model as an ensemble prediction member, together with China's T213,the United States' GFS,Japan's GPV and the European Centre's ECMWF constitutes the cyclone strong winds forecast model.Through the ensemble prediction realizes the combination between objective and subjective forecasting.The whole system uses interactive way so as to provide an effective tool for special cyclone winds forecasting,which provides a scientific basis for decision-making and reducing and preventing disaster caused by strong winds on the sea.