Early Detection of Tropical Cyclones Using Seawinds-Derived Vorticity

Abstract

A method for early detection of the systems that become tropical cyclones (TCs) in the Atlantic hurricanebasin is developed using the SeaWinds scatterometer aboard the QuikSCAT satellite. The method is based on finding positive vorticity signals exceeding a threshold magnitude and horizontal extent within the swath of vector windobservations. The thresholds applied herein are subjectively derived from the TCs of the 1999 Atlantichurricane season. The thresholds are applied to two sets of data for the 2000 season: research-quality data and near-realtime (< 3-h delay) data (available starting 18 August 2000). For the 2000 research-quality data, 7 of 18TCs had signals that were detected an average of 27 h before the National Hurricane Center (NHC) classified them as tropical depressions. For the near-real-time data, 3 of 12 TCs had signals that were detected an average of 20 h beforeNHC classification. The SeaWinds scatterometer is a powerful new tool that, in addition to other conventional products (e.g., satellite images that determine if convection is organized and persistent), could help the NHC detect potential TCs earlier.