GDACS is a cooperation framework between the United Nations, the European Commission and disaster managers worldwide to improve alerts, information exchange and coordination in the first phase after major sudden-onset disasters.

Overall Red alert Tropical Cyclone for GITA-18
in Tongafrom 09 Feb 2018 00:00 UTC to 13 Feb 2018 12:00 UTC
Storm surge for tropical cyclone GITA-18

Green alert for storm surge impact in New Caledonia

The JRC has developed an experimental global storm surge model, which is run after each advisory issued by the regional tropical cyclone centres. The calculations are published about 20 minutes after a new advisory is detected by GDACS. The calculations identify the populated places affected by storm surge up to three days in advance, using the forecasted track. When forecasts change, the associated storm surge changes too and alert levels may go up or down.

This report is for advisory number 19 of tropical cyclone GITA-18 issued at 13 Feb 2018 12:00:00 (GDACS Event ID 1000436).


Current impact estimate:

  • Population affected by cyclone-strength winds (>120km/h): 80 thousand
  • Saffir-Simpson Category: Category 4
  • Maximum sustained wind speed: 231 km/h
  • The maximum Storm surge height is  0.8m in Fuaamotu, Tonga. This height is estimated for 12 Feb 2018 11:00:00.


Previous calculations: see calculation for advisory number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Show forecast grid

Storm surge

View animation and affected locations in an interactive map: open

Storm surge maximum height
Storm surge maximum height (Source: JRC)
Storm surge animation
Storm surge animation (Source: JRC)

Affected locations

Date Name Country Storm surge height (m)
12 Feb 2018 11:00:00 Fuaamotu Tonga  0.8m
12 Feb 2018 11:00:00 Fatumu Tonga  0.8m
12 Feb 2018 11:00:00 Ohonua Tonga  0.8m
12 Feb 2018 12:00:00 Nukunuku Tonga  0.7m
12 Feb 2018 12:00:00 Houma Tonga  0.7m
12 Feb 2018 12:00:00 Pea Tonga  0.7m
12 Feb 2018 12:00:00 Nuku'alofa Tonga  0.7m
12 Feb 2018 12:00:00 Mua Tonga  0.7m
12 Feb 2018 12:00:00 Foui Tonga  0.7m
12 Feb 2018 11:00:00 Kolonga Tonga  0.5m
12 Feb 2018 11:00:00 Niutoua Tonga  0.5m
09 Feb 2018 01:00:00 Mua Wallis and Futuna  0.1m
09 Feb 2018 01:00:00 Mata-Utu Wallis and Futuna  0.1m
Locations affected by Storm surge (15 of 13)
Calculation based on advisory number 19 of 13 Feb 2018 12:00:00.
(Simulation using 0.5 minute resolution)

See full locations list (RSS)

More information

The atmospheric forcing included in the storm surge model are the pressure drop and the wind-water friction. The effects of the short waves induced by the wind (wave setup) and the precipitations are not yet implemented in the model. The model has been validated mainly in areas of shallow water (Caribbean, Bay of Bengal). Results in other basins may be inaccurate.

For a full list of available products related to this event, please refer to the GDACS Resources page.