Effects of Asymmetric Secondary Eyewall on Tropical Cyclone Evolution in Hurricane Ike (2008)

Abstract

The secondary eyewall plays an important role in tropical cyclone evolution and intensification and is routinely assumed to be axisymmetric. A unique opportunity to investigate the characteristics of the secondary eyewall in two dimensions is provided by the high spatial resolution (about 1 km) sea surface winds that were observed by spaceborne synthetic aperture radar over Hurricane Ike (2008). Here we extract the asymmetric characteristics using our Symmetric Hurricane Estimates for Winds model and analyze the related hurricane evolution by comparisons with aircraft measurements. Compared to the classic eyewall replacement cycle theory, our investigation finds that the primary eyewall did not weaken and the secondary eyewall did not shrink over a period of more than 30 hr. We suggest that the reason for this persistence is that a boundary layer inflow pathway is provided by the relatively low winds in the asymmetric secondary eyewall area, as observed by synthetic aperture radar.

Symmetric Double-Eye Structure in Hurricane Bertha (2008) Imaged by SAR

“…Therefore, the role of the axisymmetric double-eye structure in the ERC dynamic process is verified as consistent with the classic theory [15,16]. Moreover, many hurricanes are detected not to significantly weaken after the formation of the secondary eyewall [22], which may be a result of the asymmetric hurricane structure [13]. As Hurricane Bertha (2008) is relatively axisymmetric, the SFMR observed in one-dimension is supposed to represent the surface wind.…”

“…To analyze the axisymmetric double-eye structure, we adopt the definition of the complete profile [13], which contains two continuous normal profiles across the hurricane center (one is flying into the hurricane and the other is flying out). As shown in Figure 6b, there are two complete profiles composited by four normal profiles.…”

“…Additionally, hurricanes have been frequently observed by spaceborne SAR images, since the first spaceborne SAR image became available in 1978 [8]. Over the last few decades, SAR observations have been adopted in much research on hurricane readiness [9], morphology [8,10], precipitation [11], ocean surface current [12], and hurricane internal dynamic processes [13]. In this study, we present an analysis of one cross-polarized ScanSAR image from C-band RADARSAT-2 over Hurricane Bertha (2008) containing a double-eye structure.…”

Effects of Air‐Sea Interaction on the Eyewall Replacement Cycle of Typhoon Sinlaku (2008): Verification of Numerical Simulation

“…In the past few decades, aircraft reconnaissance data, satellite, and radar observations (Didlake & Houze, ; Houze et al, ; Willoughby et al, ), idealized numerical models (Kuo et al, , ; Terwey & Montgomery, ; Rozoff et al, ; Kepert, ; Wang et al, ), and fully physical atmospheric models (Judt & Chen, ; Sun et al, ; Tyner et al, ; Wu et al, ; Zhang & Perrie, ) have been widely used to study the second eyewall formation (SEF), but a firm consensus on its physical mechanisms has not yet been achieved.…”

“…In the past few decades, aircraft reconnaissance data, satellite, and radar observations (Didlake & Houze, 2013;Houze et al, 2006;Willoughby et al, 1982), idealized numerical models (Kuo et al, 2009(Kuo et al, , 2004Terwey & Montgomery, 2008;Rozoff et al, 2012;Kepert, 2013;Wang et al, 2018), and fully physical atmospheric models (Judt & Chen, 2010;Sun et al, 2013;Tyner et al, 2018;Wu et al, 2012;Zhang & Perrie, 2018) ©2019. The Authors.…”