(The color of the symbols above will change with the classification of the tropical cyclone)
Low Pressure Area or Extratropical Low
Severe Tropical Storm
Potential Track Area (70% probability)
First 72 hours
Only tropical cyclones centred within the area bounded by 7-36N and 100-140E will be shown on this website. According to the analysed position of the tropical cyclone and the tropical cyclone warning signal in force, the update time of this webpage and the information shown will be different. Details are listed in the table below:
Tropical cyclone situation
Tropical Cyclone Warning Signal No.1 or above in force
No Tropical Cyclone Warning Signal in force
Tropical cyclones centred within the area bounded by 10N and 30N, 105E and 125E.*
Other tropical cyclones centred within the area bounded by 7N and 36N,100E and 140E.**
**When a tropical cyclone forms within or enters this area, the Observatory will issue the first tropical cyclone track within two hours. When the tropical cyclone is expected to enter the area bounded by 10N and 30N, 105E and 125E in about 24 hours, the Observatory will also update the tropical cyclone track at 04:00 and 16:00 Hong Kong time (corresponding to the observation time at 02:00 and 14:00 respectively).
Detailed information of the tropical cyclone, including latitude, longitude, classification and the maximum sustained wind near centre will be shown when placing the mouse cursor over the analysed or forecast positions. The user can use the controls on the left of the map to change the area of interest and to zoom into city or even street levels. Please bear in mind the uncertainty of the tropical cyclone locations as described below in using this function.
While the forecast positions and track indicate the most likely future path of the tropical cyclone, they may deviate from the actual path taken by the storm. By pressing the 'Potential Track Area' button, the probable area within which the tropical cyclone will fall with a probability of 70% will be shown. Literally, it means that in 10 times of track forecast for similar situations, the tropical cyclone will be centred within the indicated area in about 7 times. The area grows as the forecast hour increases. It will be particularly larger beyond 72 hours and is indicated with lighter shadings on the map. The size in terms of radius of the 'Potential Track Area' corresponding to different forecast hours are determined from the error statistics of the forecasts issued in past years and are as shown in the following table:
24-hour forecast position
48-hour forecast position
72-hour forecast position
96-hour forecast position
120-hour forecast position
Short-term erratic departure of the tropical cyclone from the general direction of movement may occur from time to time. These departures are partly due to uncertainties in locating the centre of the tropical cyclone, and partly due to actual short-term variations in the direction and speed of movement of the tropical cyclone itself.
The infra-red satellite image closest to the time of tropical cyclone analysed position can be shown by pressing the 'Satellite Image' button, below which is the 'Time of image' representing the time when satellite data is completely received at the ground reception system. Since it takes time to receive and process the satellite data as well as generate the image, the time of image may somtimes be different from the time of tropical cyclone analysed position.
The Hong Kong Observatory's radar images closest to the time of tropical cyclone analysed position can be shown by pressing the 'Radar Image' button, below which is the 'Time of image' representing the time when radar completes its scan. For detailed information, please refer to the Weather Radar Image website.
The satellite images were originally captured by Multi-functional Transport Satellite (MTSAT) of Japan Meteorological Agency (JMA). Anyone wishing to further disseminate these satellite images should seek permission from JMA. (Address: Japan Meteorological Agency, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100-8122, Japan).