IMPACTS OF TWO TROPICAL CYCLONES EXPERIENCING EXTRATROPICAL TRANSITION DURING NORTHWARD PROGRESSION ON THE RAINFALL OF LIAODONG PENINSULA

Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET) process when they moved northward after landfall and affected Liaodong Peninsula. However, Matsa produced half as much rainfall as Winnie, although it struck Liaodong Peninsula directly while Winnie passed through the Bohai Sea. The relations between the ET processes and the precipitation over Liaodong Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa was closely related to the interactions between the westerly systems and typhoons during their ET processes. Winnie was captured by the upper westerly trough and then coupled with it when moving to the mid-latitudes, and the positive anomaly of moist potential vorticity (MPV) was transported downward from the upper troposphere over the remnant circulation of the tropical cyclone (TC). It was favorable to the interaction between tropical warm and wet air and westerly cold air, causing convective cloud clusters to form and develop. The rain belt composed of several meso-β cloud clusters over the Liaodong Peninsula, resulting in heavy rainfall. On the other hand, Matsa did not couple with any upper trough during its ET process and the positive anomaly of MPV in the upper troposphere and its downward transfer were weak. Only one meso-β cloud cluster occurred in Matsa’s rain belt during its ET process that tended to lessen rainfall over Liaodong Peninsula.

A DISCUSSION OF THE MOST INTENSE TROPICAL CYCLONES IN THE WESTERN NORTH PACIFIC FROM 1978 TO 2013

This study examines a number of very intense tropical cyclones(TCs) in the western North Pacific(WNP) since 1978 as depicted by the best track data from the four main weather agencies in the WNP, namely the Hong Kong Observatory, China Meteorological Administration, Regional Specialized Meteorological Centre Tokyo and Joint Typhoon Warning Centre, and the Advanced Dvorak Technique–Hurricane Satellite dataset prepared by the University of Wisconsin/NOAA National Climatic Data Center to identify the most intense TCs in the western North Pacific. Comparison analysis reveals that there are very large differences in the ranking of maximum sustained wind speed(MSW) among these datasets, probably due to data inhomogeneity issues and the discrepancies in TC intensity assessment among these centres. Re-assessment of the MSW of potential candidates suggests that, within uncertainty range of the analysis, Tip(1979) and Haiyan(2013) are the most intense TCs in the WNP during the period. Among the potential candidates, eight of them made landfall during their lifetime. Satellite pattern comparison and the best track dataset analysis of these typhoons show that Haiyan(2013) has the highest estimated MSW right before landfalling, making it the most intense TC making landfall in the WNP during the period 1978-2013.