A limited-area ensemble adjustment Kalman filter (EAKF) was employed to study tropical cyclones (TCs) over the Atlantic basin. Between 11 August and 15 September 2008, a new EAKF analysis was produced every six hours from a 96-member ensemble. The mean analyses initialized 72-hr Advanced Research Weather Research and Forecasting (WRF) model forecasts. This month-long period was very active in the tropics, as five TCs (Fay, Gustav, Hanna, Ike, and Josephine) developed, and all except Josephine made landfall.

One particularly unique aspect of this study was the direct assimilation of microwave satellite radiances with the EAKF. Although radiance assimilation is an important component of many operational global analysis systems, the impact of assimilating radiances within a regional domain is less understood. Thus, output from a configuration with radiance DA was compared to output from a parallel experiment where radiances were not assimilated. This design permitted a robust assessment of analysis and forecast sensitivity to limited-area radiance assimilation for several TC cases.

Assimilating radiances yielded improved track and intensity forecasts compared to the experiment where radiances were not assimilated, especially for mid-range lead times. These results will be presented in addition to a discussion of challenges associated with assimilating radiances using an ensemble data assimilation system.