Variations in mean annual tropical cyclone size in the Atlantic

Previous research has focused on predicting tropical cyclone (TC) size in near real time for individual storms. The purpose of this study is to develop models to explain interannual variations in mean Atlantic TC size, as measured by radius of maximum winds (RMAX) and radial extent of 34 knot winds (17 m s(-1); R34), and to identify the nature of the relationship between various environmental and storm-related characteristics and TC size. Our analysis demonstrates that mean annual TC size varies systematically among the subbasins in the Atlantic and therefore it is inappropriate to develop a single model for TC size for the entire Atlantic basin. The most important variable for explaining variations in mean annual TC size is the maximum tangential wind (VMAX). VMAX is negatively related to RMAX in all subbasins and positively related to R34 in all subbasins except the Gulf of Mexico, suggesting that years with more intense TCs tend to have smaller (larger) than average RMAX (R34). Other factors, such as the relationships between sea surface temperature, sea level pressure, and Nino 3.4 suggest that environmental factors may play a secondary role in modulating mean annual TC size. Although there are some similarities with the models developed for predicting short-term changes in TC size, our results indicate that it is not appropriate to apply these models to explain variations in TC size at larger spatial scales and longer temporal scales.