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A climate neutral year and a normal cyclone year in 2017

Substantial damages have resulted from tropical cyclones in China. 26 tropical storms or stronger events would form in North West Pacific basin and cause significant impact to the society. Though not entirely avoidable, it can to a large extent be mitigated through accurate forecasting and preparation.

Peak Re has published its first seasonal forecasting of tropical cyclone activities for 2017 in May and it expects a normal activity season this year. It has forecasted 23-25 cyclones to form which could reach to tropical storms scale.

Figure 1 Illustrates the loss statistics of tropical cyclones over the recent years.

Of the 23-25 cyclones forecasted above, 10-13 tropical storms are expected to significantly impact China and 7-8 tropical storms would make landfall over China as showed in Table 1 below.

Table 1 2017 first seasonal forecasting

One remarkable change to 2016 cyclone season is the impact to Eastern China is slightly higher than average, compare with the impacts to South China.

As a result of the strong El Niño event in 2015, late 2016 and early 2017 climate and ocean-atmosphere interaction remain at a volatile situation. At the beginning of 2017, an above average sea surface temperature (SST) over equatorial pacific was recorded (Fig 2a). There was a higher probability that 2017 would developed to an El Niño event in the first half of 2017.

Fig2a 2017 SST prediction of Nino3.4 zone
(http://iridl.ldeo.columbia.edu/maproom/ENSO)

However, the climate situation is constantly changing. Climate research indicated the likelihood of El Niño has reduced (Fig. 2b).

Fig2b 2017 SST prediction of Nino3.4 zone
(http://iridl.ldeo.columbia.edu/maproom/ENSO)

Peak Re’s May forecast is based on prior observations and subject to the uncertainties in the climate outlook.

To date, there were two events namely, No.1 ( 梅花MUIFA) and No.2 ( 苗柏MERBOK) which formed on 26th April and 11th June respectively in North Western Pacific Basin with scale reached tropical storm.

In previous report, it was presented that the long-term average tropical storm formation in the first half of the year is five events and 21 for the second half. As of today, the two events make the density of the second half of the year slightly higher than normal.