Two Step Authentication

Linfa that affected Hong Kong in early July 2015 is also an example of tropical cyclones coming from the east. In the morning of 9 July, Linfa was centred over the sea at more than 200 km to the east of Hong Kong. Being a typhoon with intact structure, it headed towards Hong Kong on a westward track. The fixed-wing aircraft jointly sent by the Observatory and the Government Flying Service recorded hurricane force winds in the vicinity of Linfa's eye, and gales of Linfa also extended out to about 100 km from its centre. As Linfa was forecast to traverse along the coast instead of moving inland, its intensity was anticipated to sustain. Local winds might also pick up quickly within a short period of time when Linfa moved further close to Hong Kong. It turned out that while Linfa skirted at just about 50 km to the north of the Observatory (Figure 5), it rapidly weakened and its gales did not affect Hong Kong generally. This formed a stark contrast to what happened with Tropical Cyclone Utor in 2001 (Figure 6). Although Utor weakened into a severe tropical storm following its landfall near Shanwei and skirted to the north of the Observatory at around 80 km inland, it was still able to bring gale force winds and heavy rain to Hong Kong for a prolonged period. 

Although the weather conditions and scientific factors in the above cases are different, all of them demonstrate that a small change can lead to a large difference. Therefore, forecasting typhoons from the east is full of challenges and their threat to Hong Kong should not be taken lightly. These cases deserve more research studies and they also serve as prime examples for considering the issuance of tropical cyclone warnings in the future.