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The Public Weather Service

Introduction :

The Hong Kong Observatory was first established in 1883 to provide a time service and to make meteorological and magnetic observations. Weather forecasts for the public first appeared in the daily publication, "China Coast Meteorological Register", in January 1895. Broadcasting of weather information to the public was introduced in the 1930's. Since then, the Hong Kong Observatory has evolved substantially and is now providing wide ranging services to the general public and a number of special users.

Hong Kong Meteorological Centre :

The Hong Kong Meteorological Centre of the Hong Kong Observatory is responsible for forecasting of the weather to meet the needs of the community. Objective forecasts of large scale meteorological patterns are received from overseas meteorological centres, such as the European Centre for Medium Range Weather Forecasts and the Japan Meteorological Agency. These forecasts are based on numerical weather prediction models and are generally satisfactory for large scale features with linear dimensions in the order of several thousand kilometres. They provide an estimate of the timing and intensity of meteorological developments up to several days ahead. To further enhance the forecast capability of rainstorms, the Hong Kong Observatory has begun operating a high resolution numerical weather prediction model since 2000. This model is capable of estimating the development of relatively small scale weather features up to 2 days ahead. In addition, the Observatory is also operating a nowcasting system which assimilates data from radars and automatic weather stations to provide objective rainfall forecast in the vicinity of Hong Kong a few hours ahead for forecasters' reference.

Forecasts and Warnings :

The Hong Kong Observatory keeps a close watch on the changing weather situation. The Hong Kong Meteorological Centre is manned 24 hours a day. Warnings of tropical cyclones and the occurrence or impending occurrence (normally within 4 hours) of severe weather such as thunderstorms, rainstorms or landslips are issued and updated as and when required. Furthermore, weather forecasts already issued are constantly reviewed in the light of new developments and are updated if necessary.

The following forecasts and warnings are issued by the Hong Kong Meteorological Centre to the public :

(a) Weather Bulletins

These are broadcast by radio and television stations in both Chinese and English. Each bulletin consists of a general description of the current weather situation and information on tropical cyclones, a weather forecast for the Hong Kong area covering the rest of the day and/or the next day depending on the time of issue of the forecast, a weather outlook and the latest readings of temperature and relative humidity.

(b) Tropical Cyclone Warnings

These warnings are issued at hourly intervals once the Tropical Cyclone Standby Signal Number 1 or a higher signal (the Strong Wind Signal Number 3, the Gale or Storm Signal Number 8, the Increasing Gale or Storm Signal Number 9 or the Hurricane Signal Number 10) is issued. The warnings contain information on the location and movement of the tropical cyclone, its intensity and the likely effects on Hong Kong. Advice to the public on the precautions to be taken is also given.

(c) Warnings of other meteorological hazards

(i) Rainstorm Warning - The Amber Rainstorm Warning Signal gives alert about potential heavy rain that may develop into Red or Black Rainstorm Warning Signal situations. It also signifies possible flooding in some low-lying and poorly drained areas. The Red Rainstorm Warning Signal warns the public of heavy rain which could cause serious road flooding and traffic congestion, and may affect schools and public examinations. The Black Rainstorm Warning Signal indicates there are major disruptions and inclement weather. People should stay home or take shelter in a safe place.

(ii) Thunderstorm Warning - Whenever thunderstorms are expected to affect Hong Kong in the short term (within one to a few hours), a brief Thunderstorm Warning Announcement will be issued. Thunderstorm warnings are issued irrespective of whether thunderstorms are widespread or isolated. If thunderstorms will affect isolated areas within a short period of time, the thunderstorm warning issued by the Observatory will indicate the areas being affected, to alert members of the public to take appropriate precautions. When thunderstorms are widespread or the areas being affected vary, it will be mentioned in the thunderstorm warning that Hong Kong will be affected by thunderstorms without specific reference to individual areas. Thunderstorm Warnings are primarily targeted at departments and organisations (including the construction, electric power and other industries; those outdoors; those at swimming pools and beaches; and those at sea) which have specific action to take to minimise loss or damage caused by lightning. The warning is also broadcast to alert the public to the potential threat of lightning. Advice on precautionary actions to be taken by individuals is given in publicity leaflets distributed by the Hong Kong Observatory.

(iii) Special Announcement on Flooding in the northern New Territories - This announcement is issued whenever heavy rain affects the area and flooding is expected to occur or is occurring in the low-lying plains of the northern New Territories.

(iv) Localised Heavy Rain Advisory - When heavy rain is recorded or is expected in individual districts of Hong Kong and may bring serious flooding and risks to the districts, the Observatory will issue the Localised Heavy Rain Advisory. The advisory indicates the affected districts and the respective rainfall recorded or expected to alert the public.

(v) Landslip Warning - A warning of landslips due to heavy rain is issued in consultation with the Geotechnical Engineering Office whenever heavy rain has occurred and is expected to continue in the next few hours such that landslips are considered to be likely.
> Hong Kong Slope Safety (Civil Engineering and Development Department) Hong Kong Slope Safety

(vi) Strong Monsoon Signal - Whenever strong monsoon is actually blowing or is forecast within the next 12 hours in the Hong Kong harbour or coastal waters, the strong monsoon signal will be issued by the Hong Kong Observatory. This warning is not used to warn strong winds associated with tropical cyclones.

(vii) Frost Warning - When the Observatory expects ground frost to occur on high ground or in the New Territories, Frost Warning will be issued to alert farmers and others concerned to take necessary precautionary measures against frost damage to vegetation.

(viii) Fire Danger Warning - This warning service is operated in co-operation with the Agriculture, Fisheries and Conservation Department to warn the likelihood of fires. A fire danger warning is issued whenever the relative humidity of the atmosphere is below certain criteria and when the vegetation is dry. A yellow fire danger warning indicates that the fire risk is high while a red fire danger warning indicates that the fire risk is extreme.

(ix) Cold Weather Warning - This warning is issued whenever cold weather is expected in Hong Kong to warn people to beware of low body temperature.

(x) Very Hot Weather Warning - When very hot and fine weather is expected, this warning is issued to warn people, particularly those engaging in outdoor activities, the risk of heat stroke and sunburn.

(d) Services to Special Users

Besides the above services which are provided free of charge to the public over the mass media, forecasts and warnings are also supplied at cost to special users through fax and direct communication links. Such users include private firms, public utilities and transport companies whose operations are weather sensitive.

Liaison with other Government Departments:

Except those issued to special users, all warnings issued by the Hong Kong Observatory are passed to the Information Services Department for onward transmission to the relevant government departments for information and action. During inclement weather conditions, the Hong Kong Observatory is in close consultation with government departments and bureaux which have special responsibilities, e.g. the Education Bureau on closure of schools and the Geotechnical Engineering Office on the issue of landslip warning.

Telephone Inquiry:

The Dial-a-Weather service can be accessed interactively by dialing a touch-tone phone to 1878200. The service provides information in Cantonese, Putonghua and English, including various weather forecasts, warnings in force, latest regional weather information, yesterday’s weather and radiation level, information on sunrise, sunset, moonrise, moonset and tide, Hong Kong standard time, weather information of major cities, etc. The public can also request weather forecasts, information sheets on weather warning systems, daily weather maps, tropical cyclone tracks and climatological information of Hong Kong, etc by fax through the service.

Internet :

The Observatory maintains a website on the Internet. The website aims at providing information on meteorology, radiation monitoring and other geophysical sciences. Its contents include weather information, warnings and forecasts for the public as well as the marine and aviation communities. Seismological, astronomical and tidal information, ultraviolet (UV) index, press releases, educational resources, information on radiation monitoring and time services are available to meet different needs of the public. A text version of the website and audio web pages are also available to facilitate accessibility by the visually impaired. The Observatory website is one of the most popular among the websites of the Government of HKSAR.

(Hong Kong Observatory website address: and