The Climate Variability and Predictability (CLIVAR) Project is an international, multi-agency campaign aimed at understanding the physical processes responsible for climate variability and predictability. The Kuroshio Extension Sytem Study (KESS) is a subset of the CLIVAR program and is a collaborative effort between the Woods Hole Oceanographic Institution, the University of Rhode Island, and the University of Hawaii. The purpose of KESS is to understand the processes that govern the variability of, and the interaction between the warm, northward-flowing waters that leave the Japanese coast to flow eastward into the North Pacific, also known as the Kuroshio Extension, and its recirculation gyre, the large oval current system to the south of the extension. For this study NCAR/EOL deployed a sounding system on a ship off of the coast of Japan, east of the Yokohama port. One hundred and forty-eight radiosonde launches were made from the ship's deck between May 29 and July 4, 2006. For more information in the CLIVAR project please visit: http://www.clivar.org/index.php or for additional information on KESS please visit: http://www.po.gso.uri.edu/dynamics/KESS/