Observational Analysis of Heavy Rainfall Mechanisms Associated with Severe Tropical Storm Bilis (2006) after Its Landfall

Abstract

This observational study attempts to determine factors responsible for the distribution of precipitation over large areas of southern China induced by Bilis, a western North Pacific Ocean severe tropical storm that made landfall on the southeastern coast of mainland China on 14 July 2006 with a remnant circulation that persisted over land until after 17 July 2006. The heavy rainfalls associated with Bilis during and after its landfall can be divided into three stages. The first stage of the rainfall, which occurred in Fujian and Zhejiang Provinces, could be directly induced by the inner-core storm circulation during its landfall. The third stage of rainfall, which occurred along the coastal areas of Guangdong and Fujian Provinces, likely resulted from the interaction between Bilis and the South China Sea monsoon enhanced by topographical lifting along the coast. The second stage of the rainfall, which appeared inland around the border regions between Jiangxi, Hunan, and Guangdong Provinces, caused the most catastrophic flooding and is the primary focus of the current study. It is found that during the second stage of the rainfall all three ingredients of deep moist convection (moisture, instability, and lifting) are in place. Several mechanisms, including vertical wind shear, warm-air advection, frontogenesis, and topography, may have contributed simultaneously to the lifting necessary for the generation of the heavy rainfall at this stage.

A vertical wind structure that leads to extreme rainfall and major flooding in southeast Australia

“…This was the case for direct model forecasts leading up to the disastrous 2011 Brisbane River and Lockyer Valley floods, which were a third of the amount actually received (van den Honert and McAneney 2011). A similar situation occurred in the disastrous 2005 Mumbai Floods (Sahany et al 2010), and in 2006 associated with one of the worst floods to affect China since 1983 (Gao et al 2009). …”

“…Direct model forecasts frequently underestimate the magnitude of maximum rainfall associated with convective processes (van den Honert and McAneney 2011;Gao et al 2009;Sandeep Sahany et al 2010). This was the case for direct model forecasts leading up to the disastrous 2011 Brisbane River and Lockyer Valley floods, which were a third of the amount actually received (van den Honert and McAneney 2011).…”

Rainfall distribution of five landfalling tropical cyclones in the northwestern Australian region

“…However, the rainfall patterns in tropical cyclones are complex and vary from case to case (Lonfat et al 2007). Rainfall forecasts of landfalling tropical cyclones are further complicated by the coastal and inland topography as well as by the land surface and boundary layer conditions, which often lead to distinct rainfall asymmetries (May et al 2008, Gao et al 2009). …”

Predictability of Tropical Cyclone Intensity Evaluated through 5-yr Forecasts with a Convection-Permitting Regional-Scale Model in the Atlantic Basin

“…It affects tropical cyclogenesis and RI (Molinari et al 2004; Molinari and Vollaro 2010b; Nguyen and Molinari 2012; Zhang and Tao 2013), TC structure (Cavallo et al 2013), and more specifically the distribution or asymmetries of convection Molinari 2002, 2003;Molinari and Vollaro 2010a;Reasor et al 2013) and precipitation (Chen et al 2006;Gao et al 2009;Wingo and Cecil 2010), as well as changes in TC intensity (DeMaria 1996; Molinari et al 2006;Zeng et al 2010). However, Zehr (2003) argued that the influence of shear might not be reliably quantified and consistently related.…”