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The principle findings of the study are as follows: 1) a new iterative condensation scheme, which limits the unphysical increase of equivalent potential temperature associated with most condensation schemes, increases the horizontal size of the hurricane, decreases its maximum rainfall rate, reduces its intensity, and makes its eye more moist; 2) in general, microphysical parameterization schemes with more categories of hydrometeors produce more intense hurricanes, larger hydrometeor mixing ratios, and more intense updrafts and downdrafts; 3) the choice of coefficients describing hydrometeor fall velocities has as big of an impact on the hurricane simulations as does choice of microphysical parameterization scheme with no clear relationship between fall velocity and hurricane intensity; and 4) in order for a tropical cyclone to adequately intensify, an advanced boundary layer scheme (e.g., Burk-Thompson scheme) must be The principle findings of the study are as follows: 1) a new iterative condensation scheme, which limits the unphysical increase of equivalent potential temperature associated with most condensation schemes, increases the horizontal size of the hurricane, decreases its maximum rainfall rate, reduces its intensity, and makes its eye more moist; 2) in general, microphysical parameterization schemes with more categories of hydrometeors produce more intense hurricanes, larger hydrometeor mixing ratios, and more intense updrafts and downdrafts; 3) the choice of coefficients describing hydrometeor fall velocities has as big of an impact on the hurricane simulations as does choice of microphysical parameterization scheme with no clear relationship between fall velocity and hurricane intensity; and 4) in order for a tropical cyclone to adequately intensify, an advanced boundary layer scheme (e.g., Burk-Thompson scheme) must be used to represent boundary layer processes. The impacts of varying simulations on the horizontal and vertical distributions of different categories of hydrometeor species, on equivalent potential temperature, and on storm updrafts and downdrafts are examined to 3 (MM5) version 3.5, are used to examine the impact of boundary-layer, and microphysical parameterization schemes on the growth and maintenance of Erin. Impacts of varying specific microphysical parameters, such as coefficients describing the fall velocities of graupel particles, on hurricane dynamics are described. A new iterative condensation scheme, developed here to limit the artificial increase of equivalent potential temperature @e that occurs during the adjustment step of many condensation schemes (Bryan and The remainder of this paper is organized as follows. Section 2 provides information on the structure and evolution of Erin based on observations acquired during CAMEX-4, concentrating on those observations that are used to assess the simulations and sensitivity studies outlined in Section 3. Section 4 describes the results of the simulations and the impacts of microphysical, thermodynamic and boundary layer that si...

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B ACKGROUND AND MOTIVATION FOR TCSP.A key mandate of the National Aeronautics and Space Administration's (NASA's) Weather Focus Area is to investigate high-impact weather events, such as tropical cyclones, through a combination of new and improved space-based observations, high-altitude research aircraft, and sophisticated numerical models to improve the understanding and predictability of weather, climate, and natural hazards. One of the areas of tropical meteorology that remains elusive to both understanding and prediction is the genesis and intensification of tropical cyclones. The processes by which tropical disturbances develop into depressions, storms, or hurricanes (termed tropical cyclogenesis) remain one of the outstanding and fascinating research topics in meteorology. The