Sunday, 31 July, 2005

Surviving Cyclones

Mumbai is a coastal city and as much as we might pretend that cyclones would never hit the city, the truth is that we will never know. Please remember that Gujarat was hit by cyclones a few years ago.
Here is a cyclone survival guide:


Tropical Cyclones are low pressure systems in the tropics that, in the Southern Hemisphere, have well defined clockwise wind circulations with a region surrounding the centre with gale force winds (sustained winds of 63 km/h or greater with gusts in excess of 90 km/h).
The gale force winds can extend hundreds of kilometres from the cyclone centre. If the sustained winds around the centre reach 119 km/h (gusts in excess 170 km/h). then the system is called a severe tropical cyclone. These are referred to as hurricanes or typhoons in other countries.

The circular eye or centre of a tropical cyclone is an area characterised by light winds and often by clear skies. Eye diameters are typically 40km but can range from under 10km to over 100km. The eye is surrounded by a dense ring of cloud about 16km high known as the eye wall which marks the belt of strongest winds and heaviest rainfall.
Structure of a Cyclone (Schematic)

Tropical Cyclones derive their energy from the warm tropical oceans and do not form unless the sea-surface temperature is above 26.5°C, although, once formed, they can persist over lower sea-surface temperatures. Tropical cyclones can persist for many days and may follow quite erratic paths. They usually dissipate over land or colder oceans.


The severity of a tropical cyclone is described in terms of categories ranging from 1 to 5 related to the zone of maximum winds. An estimate of cyclone severity is included in all tropical advices. Remember that the Warning Service is not designed to give an exact statement of conditions at individual locations but will give a general idea of the expected worst conditions. Using this severity scale, communities will be able to assess the degree of cyclone threat and take appropriate action. Damage will vary depending upon factors such as:

* How far you are from the zone of maximum winds;
* How exposed the location is;
* Building standards;
* Vegetation type; and
* Resultant flooding.

The category does not refer to the amount of flooding or storm tides. If a storm tide is expected it will be mentioned separately in the cyclone warning.

Tropical Cyclones are dangerous because they produce destructive winds, heavy rainfall with flooding and damaging storm surges that can cause inundation of low-Iying coastal areas.

Cyclones have wind gusts in excess of 90 km/h around their centres and, in the most severe cyclones, gusts can exceed 280 km/h. These very destructive winds can cause extensive property damage and turn airborne debris into potentially lethal missiles. It is important to remember that, during the passage of the cyclone centre or "eye", there will be a temporary lull in the wind, but that this will soon be replaced by destructive winds from another direction.

Heavy rainfall associated with the passage of a tropical cyclone can produce extensive flooding. This can cause further damage and death by drowning. The heavy rain can persist as the cyclone moves inland and decays, hence flooding due to a decayed cyclone can occur a long way from the tropical coast as the remains of a cyclone move into central and southern parts of the continent.

The destructive winds accompanying tropical cyclones also produce phenomenal seas, which are dangerous both for vessels out at sea and those moored in harbours. These seas can also cause serious erosion of foreshores.
Storm Surge/Tide

Potentially, the most destructive phenomenon associated with tropical cyclones that make landfall is the storm surge. Storm surge is a raised dome of water about 60 to 80 km across and typically about 2 to 5m higher than the normal tide level. If the surge occurs at the same time as a high tide then the area inundated can be quite extensive, particularly along low-lying coastlines.

The information in this checklist was prepared by Emergency Management Australia in consultation with State/Territory Emergency Services to help protect you and your property.

* Check with your local council or your building control authority to see if your home has been built to cyclone standards.
* Check that the walls, roof and eaves of your home are secure.
* Trim treetops and branches well clear of your home (get council permission).
* Preferably fit shutters, or at least metal screens, to all glass areas.
* Clear your property of loose material that could blow about and possibly cause injury or damage during extreme winds.
* In case of a storm surge/tide warning, or other flooding, know your nearest safe high ground and the safest access route to it.
* Prepare an emergency kit containing:
o a portable battery radio, torch and spare batteries;
o water containers, dried or canned food and a can opener;
o matches, fuel lamp, portable stove, cooking gear, eating utensils; and
o a first aid kit and manual, masking tape for windows and waterproof bags.
* Keep a list of emergency phone numbers on display.
* Check neighbours, especially if recent arrivals, to make sure they are prepared.

* Re-check your property for any loose material and tie down (or fill with water) all large, relatively light items such as boats and rubbish bins.
* Fill vehicles' fuel tanks. Check your emergency kit and fill water containers.
* Ensure household members know which is the strongest part of the house and what to do in the event of a cyclone warning or an evacuation.
* Tune to your local radio/TV for further information and warnings.
* Check that neighbours are aware of the situation and are preparing.

Depending on official advice provided by your local authorities as the event evolves; the following actions may be warranted.
* If requested by local authorities, collect children from school or childcare centre and go home.
* Park vehicles under solid shelter (hand brake on and in gear).
* Put wooden or plastic outdoor furniture in your pool or inside with other loose items.
* Close shutters or board-up or heavily tape all windows. Draw curtains and lock doors.
* Pack an evacuation kit of warm clothes, essential medications, baby formula, nappies,
valuables, important papers, photos and mementos in waterproof bags to be taken with
your emergency kit. Large/heavy valuables could be protected in a strong cupboard.
* Remain indoors (with your pets). Stay tuned to your local radio/TV for further information.

Based on predicted wind speeds and storm surge heights, evacuation may be necessary.
Official advice will be given on local radio/TV regarding safe routes and when to move.
* Wear strong shoes (not thongs) and tough clothing for protection.
* Lock doors; turn off power, gas, and water; take your evacuation and emergency kits.
* If evacuating inland (out of town), take pets and leave early to avoid heavy traffic, flooding and wind hazards.
* If evacuating to a public shelter or higher location, follow police and State/Territory Emergency Services directions.
* If going to a public shelter, take bedding needs and books or games for children.
* Leave pets protected and with food and water.

* Disconnect all electrical appliances. Listen to your battery radio for updates.
* Stay inside and shelter {well clear of windows) in the strongest part of the building,
i.e. cellar, internal hallway or bathroom. Keep evacuation and emergency kits with you.
* If the building starts to break up, protect yourself with mattresses, rugs or blankets under a
strong table or bench or hold onto a solid fixture, e.g. a water pipe.
* Beware the calm 'eye'. If the wind drops, don't assume the cyclone is over; violent winds
will soon resume from another direction. Wait for the official 'all clear'.
* If driving, stop (handbrake on and in gear) - but well away from the sea and clear of trees,
power lines and streams. Stay in the vehicle.

* Don't go outside until officially advised it is safe.
* Check for gas leaks. Don't use electric appliances if wet.
* Listen to local radio for official warnings and advice.
* If you have to evacuate, or did so earlier, don't return until advised. Use a recommended route and don't rush.
* Beware of damaged power lines, bridges, buildings, trees, and don't enter floodwaters.
* Heed all warnings and don't go sightseeing. Check/help neighbours instead.
* Don't make unnecessary telephone calls.

No comments:

Post a Comment