The Effect Of The Interaction Between Typhoon And Mid-latitude Trough On The Track Of Typhoon After Turning

The extratropical transition(ET) process of Tropical cyclone (TC) is very sensitive to the interaction between the decaying TC and the midlatitude circulation into which the TC is moving. Study confirmed that a the small change of the TC position or strength will lead to a larger difference of the midlatitude circulation downstream, which will also affect the TC track in the midlatitude afterwards. In order to study the error sources of TC numerical prediction during TC moving into the middle and high latitudes, the paper selected three TC cases to numerical simulate repeatedly that are initialized from sequential analyses. The results show that the prediction errors of the critical area of the interaction between TC and upper-trough exhibit a significant correlation with the track forecasting errors after TC turning, while the correlations with the errors of the upstream jet area and the subtropical high area are not significant. This is because the ET process of TC will affect the development of the mid-latitude circulation downstream, which has a certain impact on the moving path of TC after turning. And the midlatitude circulation downstream after turning is highly sensitive to the interaction between TC and the mid-latitude systems, as well as the TC track. It was also pointed out that the error correlations on different geopotential levels are different. The forecast difference and its correlation at upper levels is more significant than that at middle level, which is consistent with the the principle that the outflow is located below the tropopause. Although lower than that of upper level, the correlation at middle levels is still obvious.In addition, the TC track prediction results of sensitive experiments of Malakas and Choi-wan were analyzed in this study. The results show that, when TC enhanced (weakened) or close to (away from) the upstream trough, the interaction between TC and the upstream trough during ET process will be firmed, which leaded to the strengthen(weaken) development of the midlatitude circulation downstream. Then the trough and ridge downstream become deepen (weakened) and the zonal circulation come to strengthen (weakened). Therefore the TC forecast track was westerly (Easterly) and northerly (Southerly). This also verified the high sensitivity of ET and the TC track forecast during ET process to the interaction between TC and the midlatitude systems.