The Possibility of Determining Whether Organized Cloud Clusters Will Develop into Tropical Storms by Detecting Warm Core Structures from Advanced Microwave Sounding Unit Observations

The air temperature profiles of organized cloud clusters developing or not developing into tropical storms (TSs) over the western North Pacific in 2004 were investigated from Advanced Microwave Sounding Unit (AMSU) observations and the results of Dvorak analyses for the cloud clusters. First, typical temperature profiles of the clusters developing or not developing into TSs were compared. From this comparison, positive temperature anomalies in the upper troposphere were found in both clusters, while the values and spatial sizes of the anomalies for the clusters that developed into TS were larger than those for the ones that did not. Statistical analysis was then performed on the temperature anomalies near the center of all clusters retrieved from AMSU observational data. The average anomalies increased along with the intensity of the clusters indicated by the T-number, as estimated using the Dvorak technique. Time series analysis of temperature anomalies in the upper levels of the clusters was performed, and warm core structures were defined by the threshold derived from these anomalies. Using this definition, almost 70% of the clusters that had warm cores developed into TSs, while 85% of those that did not finally dissipated without such development. For the warm-core clusters that developed into TSs, the lead time from the detection of their warm core using AMSU observations to their recognition as TS was 27.7 hours. It is suggested that there is a strong possibility of detecting and forecasting the genesis of TSs using air temperature anomalies derived from AMSU data.