In this manual we present JET (Java Estimate Tsunami) ­ the Decision Support System for managing earthquake location, tsunami alert messages, and tsunami waveforms analysis in use at the Centro Allerta Tsunami (CAT­INGV) of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome, Italy. INGV has the responsibility for the operations of the Italian National Tsunami Warning Centre (It­ NTWC) in the framework of the NEAMTWS and as such is acting as CTSP through the CAT­INGV since October 2014. CAT­INGV has been put into service within the preexisting National Seismic Monitoring Centre at the INGV headquarters in Rome. JET has been developed by CAT­INGV to carry out the fundamental decision support operations of the the real time analysis of seismic signals, for the determination...