Surface wind field during tropical cyclone generation period by satellites

By using ADEOS/NSCAT surface wind data, we analyzed the surface wind fields over the Northwest Pacific during the tropical cyclone generation periods from September 1996 to June 1997 to try to identify the common feature related to the tropical cyclogenesis. We also utilized other datasets, such as GMS satellite data, ERS-2 surface wind data, SSM/I total precipitable water data by Wentz algorithm and global objective analysis data in Japan Meteolorogical Agency (GANAL).

We found that even before the tropical depression (< 17 m/s maximum wind speed) stage, in which no significant low-level cyclonic circulation is found, there is occasionally strong southerly surface wind of greater than 20 m/s near the low pressure area. That may give enough moisture to become to the tropical cyclone.