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Starting from 1884, a system of drum, ball and cone was employed to give information to the mariners in the harbour on the
existence and approximate location of a tropical cyclone. For the local public a typhoon gun was used to warn imminent gale force
winds brought about by tropical cyclones. In 1907, explosive bombs replaced the typhoon gun as they made louder sounds and
were considered an improvement over the firing of a gun. The last typhoon boom was exploded in 1937.
In 1917, the first numbered signal system geared to the warning of wind conditions in Hong Kong was introduced. The numbers
were from 1 to 7 with numbers 2 to 5 signifying gale force winds expected from the four quadrants. In 1931, the signals were
amended to read 1, 5, 6, 7, 8, 9, 10 with signals 5 to 8 signifying gales from the four quadrants. In 1956, the No. 3 Strong Wind
Signal was introduced between the No. 1 Stand By Signal and the gale signals.
Starting from 1 January 1973, signals 5 to 8 were replaced by 8NW, 8SW, 8NE and 8SE respectively so as to avoid
misunderstanding by the public. This system, as depicted in the following, has been in use ever since.
Originally, the signals were intended mainly for the benefits of mariners but have over the years been also adopted for use by the
public.
Stand By Signal No. 1
Nighttime Lights:
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A tropical cyclone is centred within about 800 kilometres (km) of Hong Kong and may later affect Hong Kong. Hong Kong is
placed in a state of alert because the tropical cyclone is a potential threat and may cause destructive winds later.
Points to Note:
- Listen to the radio or watch the TV for further weather information.
- Some preliminary precautions against damage should be taken now.
- Owners of small craft should ensure that their moorings are in good conditions and adequate.
- You should take the existence of the tropical cyclone into account in planning your activities.
- If you are planning to visit any of the off-shore islands or remote parts of Hong Kong over the weekend, you are reminded that deterioration in weather may affect your plans.
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Strong Wind Signal No. 3
Nighttime Lights:
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Strong wind expected or blowing, with a sustained speed of 41-62 kilometres per hour (km/h) and gusts which may exceed 110
km/h. The timing of the hoisting of this signal is aimed to give about 12 hours advance warning of a strong wind in Victoria Harbour
but the warning period may be shorter for more exposed waters.
Points to Note:
- You are advised not to delay in taking all precautions to protect your home or property. Make sure now that all loose objects, particularly on balconies and roof tops, are secure.
- Porch furniture, flower pots and other objects likely to be blown away should be taken indoors.
- Check again and make sure all windows and doors can be securely locked.
- Storm water drains should be cleared of leaves and rubbish, this applies particularly to dwellers in low-lying areas.
- Engineers, architects and contractors are again reminded that all scaffoldings, hoardings and temporary buildings should be secured.
- Small craft owners should now complete arrangements for the safety of their boats.
- Fishing vessels not yet in typhoon shelters should seek shelter without delay. Check again that all deck fittings are firmly fastened. If available, heavy anchors should be prepared and used in addition to regular anchors.
- Ships in port normally leave for typhoon anchorages or buoys.
- For safety reasons, it is suggested that all outdoor activities should be cancelled.
- Since sea state is very rough, you are advised to stay away from the shoreline and not to engage in water sports.
- Listen to your radio or watch your TV for further weather broadcasts.
- Ferry services may soon be affected by wind or waves.
- Even at this stage heavy rain accompanied by violent squalls may occur.
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Northwest/Southwest/Northeast/Southeast Gale or Storm Signal No. 8
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| Gale or storm expected or blowing, with a sustained wind speed of 63-117 km/h from the quarter indicated and gusts which may exceed 180km/h. The timing of the replacement of the Strong Wind Signal, No. 3 , by the appropriate one of these four
signals is aimed to give about 12 hours advance warning of a gale in Victoria Harbour but the sustained wind speed may reach 63 km/h within a shorter period over more exposed waters. Expected changes in the direction of the wind will be indicated by
corresponding changes of these signals.
Points to Note:
- Complete all precautions as soon as possible. It is extremely dangerous to dalay precautions until the hoisting of No. 9 and No. 10 signal as the latter are signals of great urgency.
- Complete all precautions in your home. Lock, shutter or bolt all windows and doors, fir bars into position and insert reinforced shutters and gates if they are available. Adhesive tape fixed to large window-panes in exposed positions will reduce
damage by broken glass.
- Storm water drains should be cleared of leaves and rubbish.
- Park your car where it is least likely to be damaged.
- Weather information is being broadcast at the 15th, 30th, 45th and 58th minute of each hour. Please listen to your radio or watch TV for the weather broadcasts.
- Do not stand near windows on the exposed side of your home. Move all furniture and valuables away from these areas. Make sure you have a safe place to shelter, should windows be broken.
- Owners of neon signs are reminded that they should now arrange for the electricity supply to their signs to be cut off.
- For safety reasons, it is suggested that all outdoor activities should be cancelled.
- Since seas are very rough, you are advised to stay away from the shoreline and not to engage in water sports.
- Stay indoors when the winds increase to avoid flying debris, but if you must go out, keep well clear of overhead wires or hoardings.
- All schools and law courts close and ferries will probably stop running at short notice.
- The sea level will probably be higher than normal particularly in narrow inlets. If this happens near the time of normal high tide then low lying areas may have to be evacuated very quickly.
- Heavy rain may cause flooding, rockfalls and mudslips.
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Increasing Gale or Storm Signal No. 9
Nighttime Lights:
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Gale or storm expected to increase significantly in strength. This signal will be hoisted when the sustained wind speed is expected to increase and come within the range 88-117 km/h during the next few hours when the tropical cyclone moves closer
to Hong Kong.
Points to Note:
- Since seas are very rough, you are advised to stay away from the shoreline and not to engage in water sports.
- Do not go outside. If you are reasonably protected, stay where you are and keep well away from all windows. Close all interior doors and make sure children are confined to the least exposed part of your home. On no account should you touch electric
cables that have been blown loose.
- Stay away from exposed windows and doors because glass, already under strain from wind pressure, will shatter if a flying object should hit it. Make sure you have a safe place to shelter, should windows be broken. You should only fix broken windows
and doors when there is no danger in doing so.
- If you are away from home and cannot returned fairly soon, find a safe place and remain there until the danger is over.
- The signal implies that the centre of a severe tropical storm or a typhoon will come close to Hong Kong. If the eye passes over Hong Kong, there will be a temporary lull lasting from a few minutes to several hours. This will be followed by a sudden
resumption of violent winds from a different direction. Remain where you are if protected and be prepared for destructive winds and the change in wind directions.
- Whether or not the No. 10 Signal needs to be hoisted will depend on the irregular movement of the storm caused by orographic effect as the tropical cyclone approaches land, and the consequential effects on the wind strength in Hong Kong.
- The No. 10 Signal is usually hoisted only if the tropical cyclone is of typhoon intensity and it is about to come very close or pass over Hong Kong.
- Listen to radio and television broadcasts for the latest tropical cyclone warnings.
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Hurricane Signal No. 10
Nighttime Lights:
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Hurricane force wind expected or blowing, with sustained speed reaching upwards from 118 km/h and with gusts that may exceed 220 km/h. This signal is hoisted as soon as there are definite indications that the sustained wind speed anywhere near sea
level in Hong Kong is likely to exceed 117 km/h.
Points to Note:
- Since seas are high, you are advised to stay away from the shoreline and not to engage in water sports.
- Do not go outside. If you are reasonably protected, stay where you are and keep well away from all windows. Close all interior doors and make sure children are confined to the least exposed part of your home. On no account should you touch electric
cables that have been blown loose.
- Stay away from exposed windows and doors because glass, already under strain from wind pressure, will shatter if a flying object should hit it. Make sure you have a safe place to shelter, should windows be broken. You should only fix broken windows
and doors when there is no danger in doing so.
- If you are away from home and cannot returned fairly soon, find a safe place and remain there until the danger is over.
- The signal implies that the centre of a severe tropical storm or a typhoon will come extremely close to Hong Kong. If the eye passes over Hong Kong, there will be a temporary lull lasting from a few minutes to several hours. This will be followed by
a sudden resumption of violent winds from a different direction. Remain where you are if protected and be prepared for destructive winds and the change in wind directions.
- Listen to radio and television broadcasts for the latest tropical cyclone warnings.
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Other Important Points
When the tropical cyclone is moving away from Hong Kong, danger is expected to persist outdoors for some time. You are advised to stay indoors until winds moderate and it is safe to go out. On no account should you touch electric cables that have been
blown loose. As violent squalls are still occurring in places, precautions should not yet be relaxed.
Simply knowing what signal is displayed is not enough. It is important to realise that whilst the Tropical Cyclone Warning Signals give warnings of winds expected or blowing near sea level over open water and similarly exposed areas, they do not
specifically warn of other dangers which may result from the tropical cyclone. These include flooding in low lying areas as a result of a storm surge which may cause the sea level to rise considerably higher than is normal and the destructive effects of very
heavy rain which usually accompanies tropical cyclones. This rain can cause flooding, landslips and ground subsidence. Small streams can turn into raging torrents with a short period bringing danger to anyone in their vicinity. Rocks may be dislodged from
hillsides and there may be mudslips. It is therefore important that you should listen to broadcast weather bulletins to obtain information on all adverse weather so that you may take appropriate precautions against violent winds, heavy rain and storm
surges.
The direction from which the wind is blowing, the direction towards which a tropical cyclone is moving and the bearing of its centre from Hong Kong are each given to the nearest point of 16-point compass bearing. Thus the actual bearing will be within
11¼o of the reported value.
For example, the centre of a typhoon on any bearing between 79o and 101o and moving on any heading between 259o and 281o is said to be...
"...centred...east of Hong Kong and moving west..."
It will be seen that this statement does not necessarily mean that the centre is heading directly towards Hong Kong as its course could be as much as 22o of the direct collision course.
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Tropical Cyclone Warnings