Tropical Cyclone Track Modified by a Front Located to the Northeast

Abstract

In the western North Pacific, as a tropical cyclone (TC) translates northward and approaches the midlatitude jet region, a front is often observed to the northeast of the TC, especially in fall. Theoretically, a front accompanies positive vorticity in the lower troposphere because convergence of cross-frontal circulation generates positive vorticity. Horizontal winds accompanied by positive vorticity along a front can impact the TC track. This study estimates the influence of frontal positive potential vorticity (PV) on the TC track using reanalysis data for a case of TC Chan-hom (2020). Horizontal winds due to frontal PV (FPV) are calculated using PV inversion. The FPV produces west-southwesterlies around the TC center just after the FPV formation. Thereafter, it mainly produces northwesterlies. Steering flow due to the FPV displaces Chan-hom 50 km east-southeastward for 72 h.