Table 3.

Timeline of events for Cyclone Cody⁸⁸ and the HTHH eruption⁸⁹ and tsunami^34,90

Date	Time and events
Sun 2 Jan	Time not available •Minor volcanic activity is observed in satellite imagery of Hunga Tonga-Hunga Ha’apai (HTHH).
Tues 4 - Thurs 13 Jan	Time not available •A low-pressure system is detected by the Fiji Meteorological Service (FMS) which is designated as Tropical Disturbance 03F on 5 January. From 8 to 10 January TD 03F is upgraded to a Category 2 Cyclone and is named Cody. •The FMS issues several heavy rain and severe flood alerts and warnings throughout Fiji from 4 to 8 January. The storm results in 1 death and 4,500 evacuees in Fiji. •From 10 to 13 January the NZ MetService forecasts Cody to pass near the Northeast coast of the North Island, causing higher wind and wave activity for much of the North Island, including eastern Northland toward the weekend. High levels of uncertainty in the forecast track. •On 13 January Cody weakens to a Category 1 and enters the NZ area of responsibility. NZ MetService updates the forecast track with higher confidence and advises “dangerous coastal conditions” to be felt along the eastern coast of the North Island with 6-8m waves, coastal flooding and damaging wind. •The NZ Coastguard publishes advice for mariners to prepare for Cody.
Fri 14 Jan	04:20 NZDT •A subaerial eruption begins at HTHH and generates a mushroom-shaped eruption plume. •Tsunami warnings are issued for Tonga. Fluctuating tsunami waves are recorded off the coast of Tongatapu throughout the day. 07:00 NZDT •The NZ MetService issues a Heavy Rain Watch for Gisborne and Wairoa District and expresses a high confidence of large easterly swells affecting eastern coastlines with potential for hazardous waves and rip currents from Saturday onwards.
Sat 15 Jan	00:43-06:04 NZDT •An intermittent eruption at HTHH in Tonga occurs. 07:00 NZDT •The NZ MetService publishes a new forecast track for Cody with higher confidence. The track shows an eastward shift resulting in reduced impacts from winds and rain. However, impacts on the sea conditions along the eastern coastline of the North Island remain. •Wave heights are increasing along the coastline of Northland, NZ ahead of Cody’s transit east of the country. High easterly swells are expected to spread east throughout the day and over the weekend. •The NZ MetService advises that these large waves are likely to be significant with potentially hazardous surf and swell conditions for coastal residents and recreational activities. This includes the possibility of hazardous rip currents closer to shore, and significant sea surges and coastal inundation. Things are expected to gradually ease Tuesday into Wednesday from the north. 07:20 NZDT •An ash plume rising to 14km altitude is detected over HTHH in Tonga due to an eruption that lasts 10–15 min. 10:00 NZDT •The tsunami warning in Tonga for Tongatapu, Ha’apai, and southern Tonga due to the Nuku’alofa is canceled. 17:14 NZDT •A larger submarine eruption at HTHH in Tonga begins from vents just below the surface of the ocean, generating a large ash plume. The eruptive activity lasts 8 min and the plume rises to 15.2km. •Tsunami waves ranging from 1 to 15m high and 200m inland reach Nuku’alofa, Mango Island, Tongatapu, 'Eua, and Ha’apai Islands in Tonga. Coastal roads and properties are damaged by the tsunami, all homes on Mango Island are destroyed. •4 deaths are caused by the tsunami in Tonga. •A communications blackout occurs in Tonga due to the eruption damaging a submarine fiber-optic cable and satellite terminants. Ash fall is widespread. 18:00 NZDT •Ashfall measuring several centimeters thick begins and lasts for approximately 10 h In Tonga. This contaminates water tanks and causes breathing problems for residents due to ash in the air. 18:08 NZDT •The initial tsunami threat for NZ was assessed by NEMA to be no threat, with monitoring continuing. 20:14 NZDT •NEMA upgrades the threat assessment for NZ to a Beach and Marine Advisory based on observations on the DART Buoy network. NEMA issues a NATIONAL ADVISORY: TSUNAMI ACTIVITY – EXPECT STRONG AND UNUSUAL CURRENTS AND UNPREDICTABLE SURGES AT THE SHORE (Table 2). The message applies to coastal areas on the north and east coast of the North Island and the Chatham Islands. 21:29 NZDT •Northland Regional Council in NZ receives reports of a precautionary evacuation of a campground in the Far North after elevated sea levels/wave heights are observed. 21:34 NZDT •Wave activity in Tūtūkākā Marina, Northland, NZ escalates. 21:49 NZDT •Northland CDEM receives reports of damage in Tūtūkākā Marina, Northland, NZ including damage to marina infrastructure and boats. People in the marina (on land and on their boats) evacuate to higher ground. 23:00 NZDT •Approximate end of damaging surges in Tūtūkākā Marina, Northland, NZ. No injuries or deaths reported in NZ.
Sun 16 Jan	07:33 NZDT •NEMA issues an update to the ongoing National Advisory for Tsunami Activity that tsunami activity continues to be observed. 09:40 NZDT •NEMA issues another update to the ongoing National Advisory for Tsunami Activity, extending the advisory area to include the west coast of the South Island. 19:06 NZDT •NEMA cancels the national tsunami advisory stating that based on ocean observations the Beach and Marine threat has passed for all areas. People are advised to remain vigilant and take extra precautions with regards to beach and ocean activities due to the continuation of strong and unusual currents and unpredictable surges for up to 24 h in some locations around the country.