Three events of an early stage of typhoon were captured by PALAU2013 observational network in June. All of the initial disturbances corresponded to a kind of easterly waves with vortical structures, and after passing through the Palau Islands, they developed into typhoons on the Philippine Sea. As these typhoons caused strong surface westerly winds in the formative stage, they represented a close relation to the monsoon onset and intensification of the MJO activity over the tropical western Pacific.
One of meso-scale convective systems (MCSs) propagated westward over the range of the radars on 15 June 2013, and developed into typhoon LEEPI. We launched several HYVISs into the MCS to catch the vertical profiles of ice particle's properties (type, size, and number concentration). The first HYVIS, which observed the transition region just behind the convection, captured super-cooled water droplets and several types of snow crystals (column, column-with-plate, and plate) in different height level respectively. The second and the third HYVISs were launched into the stratiform region, and showed that the identified height of each particle type gradually descended. These indicated that the ice particles were presumed to be mainly formed in the convective region, and transported into the stratiform region with gravitational sedimentation. These features were in good agreement with polarimetric parameters detected by the radar measurements.