Downshear Reformation of Tropical Cyclones

Suny At Albany, Albany NY

Investigators

Abstract

Tropical cyclones (i.e., hurricanes) are among the costliest natural disasters in terms of life and property, making forecasts of their strength and path of paramount societal and economic importance. One of the most challenging aspects of forecasting tropical cyclone strength and track occurs when a secondary storm center forms and intensifies in the thunderstorm clouds around the storm and takes over as the new storm center, a process called “downshear reformation”. This project seeks to improve understanding of how environmental factors (e.g., moisture and winds) and processes internal to the tropical cyclone itself (e.g., clouds and precipitation) affect tropical cyclone strength and track during downshear reformation. These factors are currently poorly understood and have been studied in only a handful of case studies, motivating the need for further investigation. The factors hypothesized to be important in downshear reformation include the strength and structure of the vertical wind shear (how the winds change strength and direction with height above the storm), ventilation (the injection of environmental air into the storm), and asymmetries in humidity and how the storm draws energy from the ocean (e.g., surface fluxes). These hypothesized factors will be evaluated using observational and numerical modeling approaches through identifying downshear reformation and non-downshear reformation cases that are similar to one another in terms of initial storm strength, comparing the hypothesized factors between these cases to identify which factors are important in differentiating whether downshear reformation occurs, and understanding how the new center development is governed by relevant factors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.