Some Implications of Core Regime Wind Structures in Western North Pacific Tropical Cyclones

Abstract

In this study, a tropical cyclone (TC) is considered to be compact if 1) the radius of maximum wind or the maximum tangential wind is smaller than what would be expected for an average tropical cyclone of the same intensity or the same radius of maximum wind, and 2) the decrease of tangential wind outside the radius of maximum wind is greater than that of an average TC. A structure parameter S is defined to provide a quantitative measure of the compactness of tropical cyclones. Quick Scatterometer (QuikSCAT) oceanic winds are used to calculate S for 171 tropical cyclones during 2000-07. The S parameters are then used to classify all of the cases as either compact or incompact according to the 33% and 67% percentiles. It is found that the early intensification stage is favorable for the occurrence of compact tropical cyclones, which also have a higher percentage of rapid intensification than incompact cases. Composite infrared brightness temperature shows that compact tropical cyclones have highly axisymmetric convective structures with strong convection concentrated in a small region near the center. Low-level synoptic patterns are important environmental factors that determine the degree of compactness; however, it is believed that compact tropical cyclones maintain their structures mainly through internal dynamics.

A Statistical Analysis on the Dependence of Tropical Cyclone Intensification Rate on the Storm Intensity and Size in the North Atlantic

“…The decreasing trend of IR with the increase in AR34 for AR34 larger than 150 km suggests that smaller outercore size or compact structure favors RI, as also shown in Chen et al (2011). Note that for a given intensity and RMW, a larger AR34 indicates a slow decaying rate for the tangential wind with radius outside the RMW.…”

“…Recent observational studies have begun to focus on the potential impact of TC structure on its intensification (Chen et al 2011;Rogers et al 2013;Carrasco et al 2014). Chen et al (2011) found that compact TCs (either small RMW, or weak outer-core wind, or both) had a higher IR and more frequent rapid intensification (RI) relative to incompact storms over the western North Pacific.…”

A Tale of Two Rapidly Intensifying Supertyphoons: Hagibis (2019) and Haiyan (2013)

“…5). A value of during-TC SST near 30°C under intense TC-ocean interaction is one of the highest reported over STY Megi (Lin et al 2013;D'Asaro et al 2014 showing small-RMW TCs are more likely to undergo RI (Emanuel 1989, Chen et al 2011, Carrasco et al 2014, Xu and Wang 2018. As RI began, both STYs had a substantial contraction of their RMW, but Hagibis's RMW contracted more rapidly than Haiyan (~30 km to ~10 km in 6 h vs.18 h, respectively) during P1.…”

Landfalling tropical cyclone characteristics and their multi‐timescale variability connected to monsoon and easterly formation environments over the western North Pacific

“…Previous studies confirmed that TC landfall impacts (e.g. rainfall and wind) are affected by TC characteristics including track direction (Lee et al, 2006;Chan et al, 2019), intensity (Emanuel, 2005;Yu et al, 2017), size (Matyas, 2006;Chen et al, 2011), translation speed (Su et al, 2012;Hsu et al, 2013), duration (Done et al, 2018), asymmetric structure (Lonfat et al, 2004;Chen et al, 2016), as well as interactions among these characteristics (Teng et al, 2020a). Landfall impacts are also affected by the interaction of TCs with the land surface, causing phase-locked wind and rainfall patterns (Chang et al, 1993;Lin et al, 2001;Chiao and Lin, 2003;Hsu et al, 2013;Lu et al, 2018).…”