Structure and mechanism analysis of a Jiang-huai cyclone with an eastern path and heavyrain based on NCEP data

The analysis of the structure and mechanism of a Jiang-huai cyclone with an eastern path that occurred during 1-2 May 2015 was carried out using conventional observations, NCEP 1°×1° reanalysis data and water vapor images from FY-2E. Results showed that: (1) Jiang-huai cyclogenesis occurred under the conditions of a trough at 500 hPa, a low center at 850 hPa, a cold front and inverted trough at surface, which weakened with an eastern moving path. (2) The Jiang-huai cyclone was a shallow low with weak frontal zone in the lower troposphere, which is different from the deep lows of the classical extra-tropical cyclone. The positive relative vorticity tilted westward with height during the Jiang-huai cyclogenesis The positive relative vorticities at different levels were vertically overlapped while it weakened. (3) Heavy rain was caused by abundant moisture air, strong upward vertical velocity associated with the trough at 500 hPa, the low center and shear line in the low-middle troposphere, Jiang-huai cyclone and orographic uplift. (4) The Jiang-huai cyclone moved into its eastern regions with warm advection, differential vorticity advection between the upper level and low level, and upward vertical velocity in the middle troposphere.