This paper uses a combination of AVN model data, satellite data, surface and upper air observational data and radar data to examine the rapid intensification of a tropical cyclone that moved quickly through the Mariana Islands. A developing tropical disturbance, that became Typhoon Krosa (24W), moved from north of Chuuk through the Marianas during the period 01 to 04 October 2001. This tropical cyclone began as an exposed low-level circulation with relatively little convection until it reached the base of a warm surface trough located over and just to the east of the Marianas. Data shows two surface troughs developed in association with two TUTT cells that coupled and formed a negatively tilted upper level trough located over and to the northwest of Guam. One of the surface troughs was a distal reflection of a TUTT cell, and the second trough was a warm trough associated with convection stretching northward from the circulation north of Chuuk and located to the east of the north-south axis formed by the two TUTT cells.