Major part of a formation process of Typhoon REX(T9804) was observed by the Japan Meteorological Agency research vessel (R/V) Keifu Maru radar around (20N,130E) in the north western Pacific during 23 to 24 August 1998. During that period, REX passed northward near the ship as intensifying from low pressure area into tropical depression (TD). Structure and evolution of convection in the central part of the forming Typhoon REX was analyzed mainly using the R/V Keifu Maru radar, maritime and upper air observation data.
An almost circular precipitation band system with diameter about 200 km was once formed in a lower (700hPa) level cyclonic circulation (LLCC) with wind speed about 20m/s. After that, a convective system with horizontal scale of several tens of kilometers was organized around the central area of the LLCC and developed gradually as the almost circular band system was dissipating. The developing convective system which possessed rigid appearance with maximum horizontal scale about 300km in its mature stage and longer lifetime over 15 hours was a kernel structure of REX in pre-TD to TD stage. Results of upper air observation indicate that the near surface inflow into the center of LLCC prevailed below 700hPa level, which implies an importance of the near surface inflow for the formation and maintenance of the mesoscale(300km) kernel convective system.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner