Toward better assessment of tornado potential in typhoons: Significance of considering entrainment effects for CAPE

Abstract

The characteristics of typhoons that spawned tornadoes (tornadic typhoons: TTs) in Japan from 1991 to 2013 were investigated by composite analysis using the Japanese 55 year Reanalysis and compared with those of typhoons that did not spawn tornadoes (nontornadic typhoons: NTs). We found that convective available potential energy (CAPE), which considers the effects of entrainment (entraining CAPE: E‐CAPE), and storm‐relative environmental helicity (SREH) are significantly large in the northeast quadrant of TTs where tornadoes frequently occur and that E‐CAPE and SREH in that quadrant for TTs are larger than those for NTs. On the other hand, ordinary CAPE without entrainment does not account for the spatial distribution of tornado occurrences nor does it distinguish TTs from NTs. E‐CAPE is sensitive to humidity in the midtroposphere; thus, it is effective for detecting a conditionally unstable layer up to about 550 hPa, which is distinctive of TTs.

Evolution of a Tornado and Debris Ball Associated With Super Typhoon Hagibis 2019 Observed by X‐Band Phased Array Weather Radar in Japan

“…The two‐dimensional structure of multiple and quasi‐concentric vortices in a tornadic supercell observed by mobile Doppler radar have been reported (Wurman & Kosiba, 2013). Three tornadoes generated in mini‐supercells associated with a typhoon on the Kanto Plain were reported based on C‐band Doppler radar (Suzuki et al., 2000). The mesocyclones in the mini‐supercells had smaller diameters and their locations were at lower levels compared to those of classic supercell storms observed in the United States (Lemon & Doswell, 1979).…”

Simultaneous and collocated tornado and flash flood warnings associated with tropical cyclones in the contiguous United States

“…Simultaneous and concurrent tornadoes and flash floods associated with TCs are likely a global phenomenon, much like TCs themselves. The Caribbean islands, particularly Cuba, are vulnerable to TC tornadoes (Edwards, 2012), and several studies have been devoted to TC tornadoes in East Asia (Mashiko et al ., 2009; Sueki and Niino, 2016; Bai et al ., 2017). Torrential TC rainfall and associated flooding has been observed globally as well (Kostaschuk et al ., 2001; Reason and Keibel, 2004; Terry et al ., 2008; Villarini and Denniston, 2016; Khouakhi et al ., 2017).…”

Environmental analysis on the first documented tornado outbreak in China

“…The updated T vp of the resulting mixture is determined by the new profile of equivalent potential temperature for the air parcel (e.g., Jensen and Del Genio, 2006), where represents the environmental equivalent potential temperature. In the present study, the E‐CAPE was calculated following the work in Sueki and Niino (2016) and assuming a constant mass entrainment rate of 40% km −1 (Bai et al ., 2020). Figure 2c shows that the large‐value (exceeding 50 J·kg −1 ) area of the E‐CAPE is concentrated in the northeast quadrant, generally consistent with the tornado locations.…”

“…The intrusion of dry air is believed to destabilize the storm environment by steepening the lapse rate through the midlevel evaporative cooling and increasing surface heating. Sueki and Niino (2016) also documented that the convective available potential energy (CAPE) which considers the effect of the entrainment of environmental air (entraining‐CAPE or E‐CAPE) exhibits a good performance on accounting for the spatial distribution of TC tornadoes. In the dynamic perspective, TC tornadoes tend to occur in the northeast quadrant where typifies an environment with enhanced low‐level shear and storm‐relative helicity (SRH) which aid in providing the necessary rotation for the formation of mesocyclone and tornado (McCaul, 1991).…”