Thermodynamic structure of tropical cyclones from dropsondes

Relative humidity has a substantial impact on the distribution of precipitation and convection in tropical cyclones. These in turn influence tropical cyclone structure and intensity change. Dry air close to the center can contribute to cold downdrafts and weakening of storms, while large lower-tropospheric relative humidity has been correlated with the potential for rapid deepening by Kaplan and DeMaria (2003). In the proposed poster, we will utilize dropsondes from the NOAA G-IV aircraft to determine the structure and variation of relative humidity in tropical cyclones. We will show the radial and vertical variation of relative humidity as a function of storm intensity. We will calculate differences in relative humidity between intensifying storms and those that are steady or weakening. In addition, we will break down the data by quadrant with respect to the ambient vertical wind shear vector. Preliminary work using a small sample of sondes from CAMEX showed that downshear mean relative humidity exceeded that upshear by as much as 40% when ambient shear was large. We are interested in the magnitude and radial-vertical distribution of moisture anomalies and their dependence upon the strength of the ambient shear.