Analyzing Simulated Convective Bursts in Two Atlantic Hurricanes. Part II: Intensity Change due to Bursts

Abstract

This paper investigates convective burst (CB) evolution in Weather Research and Forecasting (WRF) Model simulations of two tropical cyclones (TCs), focusing on the relationship between CBs and TC intensity change. Analysis of intensity change in the simulations shows that there are more CBs inside the radius of maximum winds (RMW) during times when the TCs are about to intensify, while weakening/steady times are associated with more CBs outside the RMW, consistent with past observational and theoretical studies. The vertical mass flux distributions show greater vertical mass flux at upper levels both from weaker updrafts and CBs for intensifying cases. The TC simulations are further dissected by past intensity change, and times of sustained intensification have more CBs than times when the TC has been weakening but then intensifies. This result suggests that CB development may not always be predictive of intensification, but rather may occur as a result of ongoing intensification and contribute to ongoing intensification. Abrupt short-term intensification is found to be associated with an even higher density of CBs inside the RMW than is slower intensification. Lag correlations between CBs and intensity reveal a broad peak, with the CBs leading pressure falls by 0–3 h. These relationships are further confirmed by analysis of individual simulation periods, although the relationship can vary depending on environmental conditions and the previous evolution of the TC. These results show that increased convection due to both weak updrafts and CBs inside the RMW is favorable for sustained TC intensification and show many details of the typical short-term response of the TC core to CBs.