sentences:  Large swells from the storm also washed rocks onto the roads near Exmouth.Late on 20 April, the JTWC, TCWC Jakarta and TCWC Perth all started to monitor a tropical low that had developed within the monsoon trough, about 1030 km (640 mi), to the south-west of Jakarta, Indonesia.During 21 April, convection surrounding the system rapidly developed in generally favourable conditions and organized around a low level circulation centre.