A Composite Perspective of the Extratropical Flow Response to Recurving Western North Pacific Tropical Cyclones
Summary (1 min read)
1. Introduction
- Tropical cyclones (TCs) undergoing extratropical transition (ET), a change from a warm-core, axisymmetric system to a cold-core, asymmetric system (e.g., Klein et al.
- 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).
- The large-scale extratropical flow response to TC recurvature also depends on the interaction of the TC with disturbances in the extratropical flow.
2. Methodology
- A. Recurvature-relative compositing methodology A point of maximum interaction is not identified for 20 of the 292 recurving TC cases because the negative PVadvection by the irrotational wind associated with the TC never exceeds an arbitrary threshold of 1PVUday21 (1PVU 5 106Kkg21m2 s21).
- For the remaining 272 recurving TC cases, those associated with an interaction metric in the top quintile are categorized as strong interactions (N5 54), whereas those associatedwith an interaction in the bottom quintile are categorized as weak interactions (N 5 54).
- The climatology is produced from 1979–2009 21-day running means of interactive-relative 2.58 NCEP–NCAR reanalysis fields.
- The Q vector describes the time rate of change of the vector horizontal potential temperature gradient due to the nondivergent wind.
3. Results
- A. Extratropical flow response to recurving TCs Recurvature-relative composite analyses of the upperlevel flow for all 1979–2009 recurving WNP TCs are displayed for T 2 72 to T 1 144h relative to recurvature time at 36-h intervals (Fig. 3).
- Between T 1 36 and T 1 144h (Figs. 3d–g), the RWT disperses across the North Pacific and alters the flow pattern over North America.
- Subtle differences exist in the configurations of the extratropical flow pattern relative to the recurving TC for strong and weak TC–extratropical flow interactions at the time of maximum interaction.
- During weak interactions (Fig. 9d), the patterns ofQs vectors and Qs-vector divergence are similar to the strong interaction composite (Fig. 9c), but less pronounced.
- In addition, the negative PV advection by the irrotational wind within the ridge on its western side promotes an amplification of the ridge.
4. Discussion
- The tendency for a preexisting RWT to amplify and migrate downstream in association with the recurvature of a WNP TC corroborates findings of a recent climatology (Archambault et al. 2013), case studies (e.g., Harr and Dea 2009; Reynolds et al.
- The tendency for strong interactions to exhibit stronger ascent in conjunction with stronger and broader divergent outflow than weak interactions is consistent with the tendency for strong interactions to be associated with larger and more intense TCs at recurvature than weak interactions noted by Archambault et al. (2013, their section 4e).
- It should be recognized that a strong interaction is not necessarily sufficient to induce a sustained, spatially extensive RWT response.
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Cites background or methods or result from "A Composite Perspective of the Extr..."
...The maximum interaction point is defined as the largest magnitude of instantaneous 250–150-hPa layer-averaged negative PV advection by the irrotational wind over the entire model domain (Archambault et al. 2013, 2015)....
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...As noted in Archambault et al. (2013, 2015), strong interactions tend to be associated with Rossby wave amplification and dispersion across the North Pacific to North America....
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...…Rossby wave dispersion due to ET is highly sensitive to the phasing of the recurving TC and midlatitude flow features (Ritchie and Elsberry 2007; Archambault et al. 2013, 2015) and showed the existence of a bifurcation point for the track of the TC in the trough-relative steering flow during ET…...
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...…building (e.g., Bosart and Lackmann 1995; Riemer et al. 2008; Archambault et al. 2013), in addition to the balanced flow, and triggers downstream dispersion of Rossby waves (e.g., Riemer and Jones 2010; Grams et al. 2013a; Archambault et al. 2015; Torn and Hakim 2015; Quinting and Jones 2016)....
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...…of low-PV air by the TC divergent outflow anchors the midlatitude jet, resulting in initial ridge building, a reduction of the phase speed, and a retardation in the eastward propagation of Rossby waves (e.g., Riemer et al. 2008; Riemer and Jones 2010; Grams et al. 2013a; Archambault et al. 2015)....
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References
34 citations
"A Composite Perspective of the Extr..." refers background or methods in this paper
...The PV framework used to diagnose Rossby wave amplification and dispersion in this study is complementary to the energetics framework used to diagnose downstream baroclinic development (Orlanski and Sheldon 1995) associated with Rossby wave dispersion following WNP extratropical cyclogenesis (e.g., Hakim 2003; Danielson et al. 2006) and TC recurvature (e....
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...…used to diagnose downstream baroclinic development (Orlanski and Sheldon 1995) associated with Rossby wave dispersion following WNP extratropical cyclogenesis (e.g., Hakim 2003; Danielson et al. 2006) and TC recurvature (e.g., Harr and Dea 2009; Cordeira and Bosart 2010; Keller et al. 2014)....
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33 citations
"A Composite Perspective of the Extr..." refers background in this paper
...…axisymmetric system to a cold-core, asymmetric system (e.g., Klein et al. 2000; Jones et al. 2003; Harr and Archambault 2015), may significantly perturb their environment as they recurve into the midlatitudes (e.g., McTaggart-Cowan et al. 2007; Harr and Dea 2009; Cordeira and Bosart 2010)....
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Frequently Asked Questions (2)
Q2. What are the future works mentioned in the paper "A composite perspective of the extratropical flow response to recurving western north pacific tropical cyclones" ?
The findings of this study suggest a variety of avenues for future research. For example, the onset of a trough over centralNorthAmerica following WNP TC recurvature indicated by the composite analysis of all recurving WNP TCs suggests a possible connection between recurving TCs and outbreaks of severe convection over the U. S. central plains. Although this study did not directly address predictability, it provides a potential framework in which to evaluate numerical model forecast error and uncertainty associated with the TC–extratropical flow interaction for recurving TC cases and other weather phenomena associated with divergent outflow that may impinge strongly upon the PV waveguide [ e. Many studies suggest that large numerical model forecast errors may result from a failure of the numerical model to adequately capture diabatically driven ridge amplification ( e. g., Davies and Didone 2013 ; Gray et al. 2014 ), whether associated with recurving TCs ( e. g., Henderson et al. 1999 ; Torn 2010 ), mesoscale convective systems ( e. g., Dickinson et al. 1997 ; Rodwell et al. 2013 ), or warm conveyor belts of explosively deepening extratropical cyclones ( e. g., Doyle et al. 2014 ).