The volcanic eruption on the island of Hunga-Tonga-Hunga-Ha'apai, about 30 km (19 mi) south-southeast of Fonuafoʻou island in Tonga, on Saturday 15 January 2022, generated a tsunami that caused damage locally, regionally, and across the Pacific.  This was the first time that the Pacific Tsunami Warning and Mitigation System (PTWS) responded to a volcano-generated tsunami.  Given that the PTWS is designed for earthquake-generated tsunamis, which cause nearly 90% of the world’s tsunamis, many adjustments were required during the event by the PTWS Tsunami Service Provider (Pacific Tsunami Warning Center, PTWC) and Member States.

To move forward, the PTWS immediately convened three Post-Event Briefs to share information and experience, and provide interim guidance should another volcanic eruption occur

PTWS Post-Event Brief I (20 January, 2200-2400 UTC) focused the warning aspects. The PTWS WG 2 and PTWC presented a proposal for immediate interim guidance on warnings for volcanic sources

PTWS Post-Event Brief II (3 Feb 2022, 2200-2400 UTC) updated progress on the PTWS Interim Tsunami Volcano SOP and shared country warning and response from Tonga and the nearby region

PTWS Post-Event Brief III (this meeting) will continue the agenda from Brief II, including progress on the PTWS Interim Tsunami Volcano SOP, country warning and response sharing, and discussion on lessons learned for strengthening national tsunami warning systems, and improving the PTWS.

PTWS Interim Procedures and PTWS Products for Tsunamis from the HTTH Volcano:
- PTWS Interim Procedures Implementation Plan, v1.1, 1 Mar 2022
- Task on HTHH Terms of Reference
- IOC CL 2882, Interim Volcano-generated Tsunami Alert Products and Procedures of the Pacific Tsunami Warning and Mitigation System, 18 Mar 2022

- User's Guide, PTWC Interim Procedures and PTWS Products for Tsunamis from the Hunga Tonga – Hunga Ha‘apai Volcano, 6 Apr 2022