A Climatological Analysis of the Extratropical Flow Response to Recurving Western North Pacific Tropical Cyclones

Abstract

Although prior studies have established that the extratropical flow pattern often amplifies downstream of recurving tropical cyclones (TCs), the extratropical flow response to recurving TCs has not to the authors' knowledge been systematically examined from a climatological perspective. In this study, a climatology of the extratropical flow response to recurving western North Pacific TCs is constructed from 292 cases of TC recurvature during 1979-2009. The extratropical flow response to TC recurvature is evaluated based on a timelagged composite time series of an index of the North Pacific meridional flow surrounding TC recurvature. Similar time series are constructed for recurving TCs stratified by characteristics of the large-scale flow pattern, the TC, and the phasing between the TC and the extratropical flow to assess factors influencing the extratropical flow response to TC recurvature. Results reveal that following TC recurvature, significantly amplified flow develops over the North Pacific and persists for ;4 days. The tendency for significantly amplified North Pacific flow to develop following TC recurvature is sensitive to the strength of the TC-extratropical flow interaction (the phasing between the TC and the extratropical flow), which is based on the negative potential vorticity advection by the divergent outflow of the TC. In contrast, the tendency for significantly amplified North Pacific flow to develop following TC recurvature is relatively insensitive to the intensity or size of the recurving TC, or whether it subsequently reintensifies after becoming extratropical.

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

“…The poleward and upward transport of low potential vorticity (PV) air associated with TC recurvature tends to amplify a ridge and intensify a jet streak along the meridional PV gradient marking the jet stream (e.g., Agustí-Panareda et al 2004, 2005Riemer et al 2008;Riemer and Jones 2010;Grams et al 2013a;Archambault et al 2013).…”

“…Thus, a recurving TC may indirectly reconfigure the extratropical flow pattern and influence the sensible weather thousands of kilometers downstream within a few days (e.g., Archambault et al 2013, their Fig. 1).…”

“…On average, the North Pacific flow pattern becomes significantly amplified for approximately four days following western North Pacific (WNP) TC recurvature (Archambault et al 2013). However, the extratropical flow response to TC recurvature may range from a marked flow amplification [e.g., with TC Oscar (1995); Archambault et al (2013), their Fig.…”

“…However, the extratropical flow response to TC recurvature may range from a marked flow amplification [e.g., with TC Oscar (1995); Archambault et al (2013), their Fig. 1; Harr and Archambault (2014)], to a strengthened jet stream without substantial flow amplification [e.g., with TC Jangmi (2008); Grams et al (2013a,b)], to little change in the flow pattern [e.g., with TC Opal (1997); Harr and Elsberry (2000)].…”

“…Characteristics of the recurving TC, such as size and intensity, are thought to be secondary factors (e.g., Harr and Dea 2009;Archambault et al 2013).…”