Overall Green alert Tropical Cyclone for FOUR-21
in India
click on to select bulletin time
Impact Single TC
Impact based on all weather systems in the area


Tropical Cyclone FOUR-21 can have a low humanitarian impact based on the maximum sustained wind speed,exposed population and vulnerability.

Meteorological source GDACS
Exposed countries India
Exposed population No people in Category 1 or higher
Maximum wind speed 65 km/h
Maximum storm surge n.a.
Vulnerability High (India)
Landfall between
11 Nov 2021 06:00 - 11 Nov 2021 18:00

in India


GDACS alert score for Tropical Cyclones is 0.5 (GREEN Alert), 1.5 (ORANGE Alert), 2.5 (RED Alert)
For more info on GDACS alert score click here.
  Wind Storm surge Rainfall GDACS score
Current 65 km/h n.a. n.a. 0.5
Overall 65 km/h 0.0 m n.a. 0.5

Maximum winds, storm surge, rainfall (Current: over the next 72 h, Overall: entire TC track) based on GDACS impact


65 km/h Current Max.

Up to 13.6 million people in Tropical Storm strength or higher (see SSHS)

Impact Timeline

Alert Date (UTC) Max Winds (km/h) Population in
Tropical Storm or higher
Population in
Cat 1. or higher
Green 1 11 Nov 2021 06:00 65 13.6 million No people India

Bulletin Timeline

Alert Date (UTC) Category
Max winds
Population in
Cat.1 or higher
Population in
Tropical Storm
or higher
Location (lat, lon) Countries
1 11 Nov 2021 06:00 Tropical storm 65 no people no people 13, 80.9
1 11 Nov 2021 18:00 Tropical depression 56 no people no people 13.4, 79.7 India
1 12 Nov 2021 06:00 Tropical depression 37 no people no people 13.8, 78.7 India
Actual track of the current bulletin
The alert for forecast greater than 3 days is limited to Orange level.

Exposed population - AoIs

Exposed population in the potential affected countries, provinces and populated places




Region Province Country
Tamil Nadu India
Andhra Pradesh India

Populated places

Name Region Province Country City class Population
Chennai Tamil Nadu India Major city 4.3 million people
Ambattur Tamil Nadu India City 340000 people
Sriperumbudur Pallavaram Tamil Nadu India City -
Tambaram Tamil Nadu India City 140000 people
Avadi Tamil Nadu India City 250000 people
Poonamallee Tamil Nadu India City -
Takkolam Tamil Nadu India City -
Arkonam Tamil Nadu India City -
Tirupati Andhra Pradesh India City 250000 people

Critical infrastructure

Airports, ports, nuclear plants and hydrodams at risk, if affected, are listed below.


Name IATA Code Elevation (m) Usage Runway type IFR Runway Length (ft)
Madras Chennai MAA 15 Civ. Paved Yes 12000
Tambaram 27 Mil. Paved No 5900
Arkonam 84 Mil. Paved Yes 11000
Tirupathi TIR 106 Civ. Paved Yes 7500


Name LOCODE Country
Madras INMAA India


Rainfall accumulation of the past 24h, as detected by the Global Precipitation Measurement mission of NASA. For more information, see https://www.nasa.gov/mission_pages/GPM/main/index.html.



The JRC has developed an experimental global storm surge model. 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. All links, data, statistics and maps refer to the latest available calculation. If the calculation for the last advisory is not completed, the latest available calculation is shown.