Detecting tropical cyclone structural change with the TRMM Precipitation Radar (PR), Advanced Microwave Sounding Unit (AMSU) and Multi-satellite Precipitation Analysis (MPA)

One of the most critical and complex parameters to monitor within a tropical cyclone (TC) are temperature anomalies. The maintenance of the thermal structure gives important insight into a TC’s strength and maturity that allow forecasters to warn appropriately for intensity fluctuations. The conversion of a TC’s symmetric warm core into an extratropical cyclone’s asymmetric cold core, a process known as Extratropical Transition (ET), can lead to forecasting difficulties due to the complex nature of TC thermal anomaly maintenance at higher latitudes. The potential for impact variables such as wind field expansion, rainfall enhancement, trapped fetch waves and increased storm translational speeds make forecasting for ET events a rather daunting task. The success of the Cyclone Phase Space (CPS) developed by Hart (2003) for tracking the symmetry and thermal structure of cyclones evolving between the continuum of tropical to extratropical cyclones has led to vast improvements in the forecasting and monitoring of ET systems at operational centers such as the National Hurricane Center and National Weather Service (Hart 2005, personal communication). Cyclones are moved within the phase space as a function of their thermal structure (900-600 hPa thermal wind) and symmetry (900-600 hPa stormrelative thickness symmetry) computed from gridded model analyses (Hart 2003). The regular, three-dimensional spatiotemporal frequency of global model analyses used within the CPS allows for a thorough analysis of cyclone structure by utilizing the isobaric height field produced by each model. However, the CPS suffers from inherent biases within each model such as resolution (finest horizontal resolution of 1.0°), initialization methods and vortex bogusing as well as biases between each model since varying _________________________________________ * Corresponding author address: Stephen R. Guimond, Center for Ocean Atmospheric Prediction Studies, The Florida State University, Tallahassee, FL 32304. E-mail: guimond@coaps.fsu. edu depictions of the ET process can be realized (Hart 2003). It is hypothesized that a more direct, observational approach to cyclone structure could have the potential to become synthesized with the CPS and would allow for increased accuracy in the monitoring of ET as well as validation of the current model based analyses. This paper presents the first step in an attempt to infer cyclone structural evolution from a satellite perspective by analyzing bright band heights (BBHs) retrieved from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and freezing level heights (FLHs) from the Advanced Microwave Sounding Unit (AMSU). In an effort to ameliorate the understanding and forecasting associated with impact variables during the ET process, many of which are directly related to temperature anomaly fluctuations, the initial stages of a project utilizing NASA’s multi-satellite precipitation analysis (MPA) will also be presented. The end goal of this phase of the study is a conceptual model of the precipitation organization during ET that will aid in the quantitative precipitation forecasting (QPF) of systems in both the Atlantic and Pacific Ocean basins.