In order to improve the ability to use the products of T639, a synoptic verification on its mediumrange forecasting in Spring 2011 is made in comparison with the NWP of ECMWF and Japan models. The results show that the three models have good performances on the aspect of predicting the largescale circulation evolution and adjustment in Asian middle and high latitude areas. As a whole, the ECMWF model is better in forecasting most weather systems compared with the T639 and Japan models. Taking the sandstorm process during the period of April 28-30, 2011 as a case, it is found that the Japan model is more effective than the other two models in mediumrange forecasting of strong surface wind, causing this sand and dust weather process.