Landfalling tropical cyclones(LTCs)include those TCs approaching the land and moving across the coast.Structure and intensity change for LTCs include change of the eye wall,spiral rain band,mesoscale vortices,low-layer shear lines and tornadoes in the envelope region of TC,pre-TC squall lines,remote rain bands,core region intensity and extratropical transition(ET)processes,etc.Structure and intensity change of TC are mainly affected by three aspects,namely,environmental effects,inner core dynamics and underlying surface forcing.Structure and intensity change of coastal TCs will be especially affected by seaboard topography,oceanic stratification above the continental shelf and cold dry continental airflow,etc.Rapid changes of TC intensity,including rapid intensification and sudden weakening and dissipation,are the small probability events which are in lack of effective forecasting techniques up to now.Diagnostic analysis and mechanism study will help improve the understanding and prediction of the rapid change phenomena in TCs.
Analyzed in this paper are the 20-yr(1991-2010)tropical cyclone(TC)intensity from three forecast centers in the Western North Pacific,i.e.China Meteorological Administration(CMA),Japan Meteorological Agency(JMA),and Joint Typhoon Warning Center(JTWC)of the United States.Results show that there is more or less discrepancy in the intensity change of a TC among different datasets.The maximum discrepancy reaches 22 hPa/6h(42 hPa/6h,33 hPa/6h)between CMA and JMA(CMA and JTWC,JMA and JTWC).Special attention is paid to the records for abrupt intensity change,which is currently a difficult issue for forecasters globally.It is found that an abrupt intensity change process recorded by one dataset can have,in some extreme cases,intensity change in another dataset varying from 0 to≥10 hPa/6h with the same sign or the opposite sign.In a total of 2511 cases experiencing rapid intensity change,only 14%have consensus among all the three datasets and 25%have agreement between two of the three datasets.In spite of such a significant uncertainty,the three datasets agree on the general statistical characteristics of abrupt intensity change,including regional and seasonal distribution,the relationship with initial intensity and TC moving speed,and persistence features.Notable disagreement is on very strong systems(SuperTY)and TCs moving very fast.
