Landing east or west?
- Friday, 29th July 2016
You may already be aware from the Observatory's weather forecast that a tropical cyclone may enter the northern part of the South China Sea next week and bring squally heavy showers to the coast of southern China. Some of you may even notice that certain computer models such as that from the European Centre forecast a direct hit of the tropical cyclone on Hong Kong. Nevertheless, there were discrepancies among different computer models as regards the forecast track. Some predicted a tropical cyclone making landfall over the eastern part of Guangdong while some forecast a tropical cyclone edging close to western Guangdong. Even for the European Centre itself, different members of its ensemble model forecast vastly different tracks (Figure 1).
Figure 1 The ensemble forecast results of European Centre on 28 July 2016, inclusive of forecast tracks from some 50 members. Numbers circled represent the number of days counted from the date of forecast.
Where a tropical cyclone makes landfall, e.g. to the east or to the west of Hong Kong, can result in significantly different local weather. For instance, if it lands to the east, Hong Kong will be affected by northerly winds for a while. Due to terrain effect, the wind strength over Hong Kong will be lower. In case it skirts to the south of Hong Kong and makes landfall to our west, local winds will not weaken significantly. The prevailing southeasterly winds will even push sea water towards the coast and result in storm surge. Coincidently the new moon occurs next week. There is a chance that the astronomical high tide will increase the threat of flooding brought by storm surge. The Observatory will closely monitor the impact of tropical cyclone on local weather. Please stay tuned to our weather updates.
L.S. Lee and Y.C. Chan