A Composite Perspective of the Extratropical Flow Response to Recurving Western North Pacific Tropical Cyclones

Abstract

This study investigates the composite extratropical flow response to recurving western North Pacific tropical cyclones (WNP TCs), and the dependence of this response on the strength of the TC-extratropical flow interaction as defined by the negative potential vorticity advection (PV) by the irrotational wind associated with the TC. The 2.58 NCEP-NCAR reanalysis is used to construct composite analyses of all 1979-2009 recurving WNP TCs and of subsets that undergo strong and weak TC-extratropical flow interactions.Findings indicate that recurving WNP TCs are associated with the amplification of a preexisting Rossby wave train (RWT) that disperses downstream and modifies the large-scale flow pattern over North America. This RWT affects approximately 2408 of longitude and persists for approximately 10 days. Recurving TCs associated with strong TC-extratropical flow interactions are associated with a stronger extratropical flow response than those associated with weak TC-extratropical flow interactions. Compared with weak interactions, strong interactions feature a more distinct upstream trough, stronger and broader divergent outflow associated with stronger midlevel frontogenesis and forcing for ascent over and northeast of the TC, and stronger upper-level PV frontogenesis that promotes more pronounced jet streak intensification. During strong interactions, divergent outflow helps anchor and amplify a downstream ridge, thereby amplifying a preexisting RWT from Asia that disperses downstream to North America. In contrast, during weak interactions, divergent outflow weakly amplifies a downstream ridge, such that a RWT briefly amplifies in situ before dissipating over the western-central North Pacific.

Synoptic and mesoscale processes supporting vertical superposition of the polar and subtropical jets in two contrasting cases

“…From this analysis, it is evident that the divergent wind slows the eastward translation of the subtropical tropopause break over northern Mexico, given the strip of positive PV advection found in that location in Figure . This mechanism, whereby the divergent wind slows the eastward progression of a midlatitude trough, is similar to that identified by Archambault et al (), among others, in cases of ET. Over Texas and Oklahoma, the divergent and non‐divergent wind fields appear to combine constructively to drive a region of negative PV advection.…”

“…This result aligns particularly well with existing evidence illustrating the role that tropopause‐level outflow can play in influencing the strength and location of a particular jet stream (e.g. Grams et al , , ; Archambault et al , , ). However, in contrast to the December 2009 case, ageostrophic transverse circulations played a more indirect role in the production of a superposition during the 2010 Nashville Flood.…”

“…Tropical cyclones and extratropical transition (ET) events have also been shown to exert a considerable influence on the location and strength of the subtropical jet via the negative PV advection accomplished by their tropopause‐level, divergent outflow and the diabatic erosion of upper‐tropospheric PV that accompanies intense latent heat release in the middle troposphere (e.g. McTaggart‐Cowan et al , , , ; Agusti‐Panareda et al , ; Ahmadi‐Givi et al , ; Grams et al , , ; Archambault et al , , ; Griffin and Bosart, ).…”

Downstream influence of mesoscale convective systems. Part 1: influence on forecast evolution

“…() and with tropical cyclones in a composite of such cyclones interacting with extratropical flow by Archambault et al . ().…”

European high-impact weather caused by the downstream response to the extratropical transition of North Atlantic Hurricane Katia (2011)

“…In the presence of a strong TC-extratropical flow interaction, the ridgebuilding triggers downstream development of a pronounced Rossby wave train [Archambault et al, 2013[Archambault et al, , 2015Quinting and Jones, 2015;Torn and Hakim, 2015]. Differences exist for different ocean basins.…”