Recent increase in the occurrences of Christmas typhoons in the Western North Pacific

Joseph Basconcillo,Il-Ju Moon

doi:10.1038/s41598-021-86814-x

Joseph Basconcillo, Il-Ju Moon

Open Access

https://doi.org/10.1038/s41598-021-86814-x

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Abstract

To imply the gravity of their impact on Christmas celebration, the term Christmas typhoon recently became more popular to refer to tropical cyclones (TC) in the Western North Pacific (WNP) during its less active season. The past 9 years from 2012 to 2020 saw more than 70% (210%) increases in Christmas typhoon occurrences in the WNP (Philippines). Furthermore, Mindanao Island, which is located in southern Philippines, has experienced an unprecedented 480% increase in TC passage in the same period. Here we show that the detected recent increase in Christmas typhoons are mainly associated with the shift of the Pacific Decadal Oscillation to its positive phase in early 2010s, which led to favorable changes in the large-scale environment for TC development such as higher relative vorticity, anomalous low-level westerlies, warmer sea surface temperatures in the central Pacific, and extended WNP subtropical high. We also found that the poleward shift of the Intertropical Convergence Zone and possibly, the recent recovery of the Siberian High contributed to such increased occurrences. As opposed to the more active TC season, there is a wide research gap during the less active season. We aim to fill in this knowledge gap to gain better insights on TC risk reduction.

Highlights

To imply the gravity of their impact on Christmas celebration, the term Christmas typhoon recently became more popular to refer to tropical cyclones (TC) in the Western North Pacific (WNP) during its less active season
We argue that Christmas typhoons are driven by interannual to multi-year variability but its recent increased occurrences are mainly attributed to the shifts of the Pacific Decadal Oscillation in the early 2010s to its positive phase
Using the Empirical Orthogonal Function (EOF) transform, we found that the principal component of the second leading EOF mode of precipitation in the Indo-Pacific Warm Pool region is highly correlated with Christmas typhoon frequency (r = 0.67, p < 0.01, two-tailed; (Supplementary Fig. S5d) and its highest amount of precipitation has strong resemblance (Supplementary Fig. S5b) to the location of convective anomalies in the central Pacific during the Period 2 (Fig. 3e) and in a positive Pacific Decadal Oscillation (PDO) phase (Fig. 3f), which suggests the influence of the warm pool ITCZ to Christmas typhoons

Summary

Introduction

To imply the gravity of their impact on Christmas celebration, the term Christmas typhoon recently became more popular to refer to tropical cyclones (TC) in the Western North Pacific (WNP) during its less active season. The said upsurge in the cost of damages is corroborated by the significant increase in Christmas typhoons in WNP, in the Philippines, and in Mindanao since 2012 (p < 0.001, two-tailed; Fig. 1d). It is noteworthy that 11 out of the 16 Christmas typhoons that passed over Mindanao from 1984 to 2020 are recorded in a span of 9 years from 2012 to 2020, which is one of the reasons why there is an increasing cost of damages during the LAS in the Philippines. There is an apparent lack of literature on TC variability during the L AS9,10 as opposed to the wide array of studies during the more active season We attribute this knowledge gap to the limited number of TCs during the LAS and to their regional clustering in the WNP and in the Philippines.

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