In August 2016, Peak Re and Shanghai Typhoon Institute (STI) released the updated seasonal forecast of tropical cyclone activities over Western North Pacific (WNP) and South China Sea (SCS).
In the updated forecast, 16-19 tropical storms or stronger eve nts were predicted to form over WNP and SCS. The expected number of events forming was revised downward compared to the first forecast report released in May. Other key figures, i.e. number of events impacting China, and number of landfall over China remained unchanged from the report in May.
To date, 17 named tropical cyclones with intensity higher than tropical storm were formed in WNP and SCS basin. The first event intensified to tropical storm level and received the name Nepartak in early July 2016 which was significantly later than a normal typhoon season. In summary, events were formed and travelled in two major patterns. For events formed at the east of the Philippines (orange box), they travelled in a westerly track which either made landfall over Taiwan then over South China or directly made landfall over China. For events formed over the east of Taiwan and north of the Mariana Islands (white box), they travelled in a north-eastern direction and impacted Japan.
Statistics on the event formation between 1949 and 2015 is illustrated in Fig. 2, where orange line represents the monthly average over 66 years and blue bar illustrates the monthly summary for each year. On average, event will occur every month from the beginning of the year. The activity reaches the peak in August and will last till the end of the year.
However, in 2016, no events formed between January and June as a result of the extremely strong El Nino events experienced in 2015. More importantly, a delayed season doesn’t mean an empty season. Following the first event in July, 5 more tropical cyclones (including 2 Tropical Depression) formed over WNP and SCS. 17 tropical cyclones (including 10 Tropical Depression) formed in August. This season delaying is similar to the other three years which also followed a strong El Nino event. This is clearly illustrated in table 1, the majority of indicators were below the long term averages but the activities in second half year were still sizable.
The current Sea Surface Temperature (SST) is at neutral status and is turning to a weak La Nina event in autumn or winter of 2016. Multiple institutions forecasted the La Nina events will last till April 2017 the earliest. (see Fig. 3) This pre-season signal will significantly impact the tropical cyclone activity in 2017.
(Source: iri.columbia.edu/our-expertise/climate/forecasts/enso/current/)
In order to provide internal and external parties with a more convenient solution to monitor tropical cyclone activities over WNP, Peak Re has built a web based Geographic Information System (GIS) platform to provide real-time tropical cyclone tracking. STI’s comments on the potential impacted areas for each event will also be available on the platform.
