The importance of resolved microphysics to reintensification during the extratropical transition of tropical cyclones

The possible reintensification of a transformed tropical cyclone under the influence of a midlatitude upper-level trough has been shown to be quite sensitive to the interaction geometry for idealized simulations in which other factors were held constant. Predicting the occurrence and degree of reintensification remains a challenging forecast problem. We are interested in discovering specific physical characterstics that develop during the transformation stage that can be used to understand and predict any subsequent reintensification. A previous study indicated excellent correlation between reintensification and certain synoptic and precipitation pattern features, suggesting that both types may be of use. In this study we use a numerical model, the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®), to investigate the influence of resolvable mixed-phase microphysics on the reintensification process. Both observational and modeling studies have shown how condensational latent heating can affect cyclogenesis by interacting with both the upper-level and lower-level PV fields. Here we use increased horizontal resolution to better reproduce the asymmetric vertical motion and associated precipitation fields in the vicinity of the tropical cyclone remnant center. We also specifically investigate the influence of the ice phase, which becomes increasingly important during the transformation cases shown.