Analysis of a waterspout at Zhuhai, China, on June 12, 2019

Abstract

This paper reports on a waterspout presiding over the Pearl River Estuary near Zhuhai, China. It is observed mainly using the terminal Doppler weather radar in Hong Kong. A slanting radar reflectivity core and airflow circulating around was seen in the vertical cross-section across the mesoscale/microscale cyclone associated with the waterspout. The vertical wind profile associated with the cyclone was analysed and found to exhibit characteristics similar to those of a tornado reported in the region in a previous study. The primary characteristic of the waterspout was a circulating flow stronger at higher levels (approximately a few kilometres above ground) than at lower levels. In terms of nowcasting, the performance of a convection-permitting numerical weather prediction model (2 km horizontal resolution) was analysed. It was found to demonstrate reasonable simulation skill for the mesoscale/microscale cyclone, although the slanting feature was not well predicted. The results of this study can serve as a useful reference for similar studies of waterspouts/tornadoes worldwide. K E Y W O R D Snumerical simulation, waterspout, weather radar

Observation and numerical simulation of a weak waterspout at Hong Kong International Airport

“…Around the time of the waterspout occurrence, the vertical windshear was of the order of 10 × 10 −3 s −1 , similar to that reported by Chan et al . (2020) and with observations of typhoon‐related tornados in southern China (Huang et al ., 2020). As reported in previous cases (i.e., tornados in southern and central China), relatively high vertical windshear is suspected to support the occurrence of waterspouts.…”

“…This slanting feature was also reported by Chan et al . (2020); however, the physical reasons for the slanting feature have not yet been confidently determined. Slanting during the intensification phase of tornados has been reported in the literature (e.g., Bluestein et al ., 2019).…”

“…The vertical profiles were generally consistent with those reported in Chan et al . (2020); however, the limited number of documented samples makes it difficult to establish whether the vertical profile of the wind reflects those typically associated with waterspouts/tornados over southern China. More samples should be collected to determine typical vertical wind profiles, which have many potential applications, such as engineering tall buildings to withstand winds in southern China or the development of policies to ensure severe‐weather preparedness.…”

“…In this study, the 200 m grid aviation model (AVM) implement of the HKO Weather Research and Forecast (WRF) model was used to simulate the event. The AVM focuses on fine‐scale weather evolutions around the geographically complex HKIA area and has demonstrated the ability to reproduce complex airflow features at mesoscale and microscale under a wide range of weather conditions (Chan and Hon, 2016a; 2016b; Chan et al ., 2020; Hon, 2020). At the time of the event, the operational forecast domain of the AVM comprised 581 × 581 grid points horizontally, covering an area of approximately 112 × 112 km 2 centred around HKO.…”

“…Based on records from the Hong Kong Observatory (HKO), between 1959 and 2019 only 39 waterspout sightings were reported over Hong Kong waters, representing an average of only 0.64 reported occurrences per year. Previous studies have described waterspouts over southern China in regions neighbouring Hong Kong, such as Zhuhai, which is immediately north of Macao (Chan et al ., 2020). While the observation, analysis and numerical prediction of tornados are well documented in the literature, particularly over the United States (Doswell III and Burgess, 1988; Stensrud et al ., 2009; Childs and Schumacher, 2019; Tao and Tamura, 2020), the arguably less destructive phenomenon of waterspouts has received less study (Golden, 1977; Niino et al ., 1997; Devanas and Stefanova, 2018; Rodríguez and Bech, 2018; Miglietta et al ., 2020).…”