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Journal ArticleDOI

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

TL;DR: In this paper, the authors investigated 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-extrropical interaction as defined by the negative potential vorticity advection (PV) by the irrotational wind associated with the TC.
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 2.5° 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 240° 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...

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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2015-04
A Composite Perspective of the Extratropical
Flow Response to Recurving Western North
Pacific Tropical Cyclones
Archambault, Heather M.; Keyser, Daniel; Bosart, Lance
F.; Davis, Christopher A.; Cordeira, Jason M.
Montly Weather Review, Volume 143, pp. 1122-1141, April 2015
http://hdl.handle.net/10945/45742
This publication is a work of the U.S. Government as defined in Title 17, United
States Code, Section 101. Copyright protection is not available for this work in the
United States.
Downloaded from NPS Archive: Calhoun

A Composite Perspective of the Extratropical Flow Response to Recurving
Western North Pacific Tropical Cyclones
HEATHER M. ARCHAMBAULT*
Department of Meteorology, Naval Postgraduate School, Monterey, California
DANIEL KEYSER AND LANCE F. BOSART
Department of Atmospheric and Environmental Sciences, University at Albany, State
University of New York, Albany, New York
CHRISTOPHER A. DAVIS
National Center for Atmospheric Research, Boulder, Colorado
JASON M. CORDEIRA
Department of Atmospheric Science and Chemistry, Plymouth State University, Plymouth, New Hampshire
(Manuscript received 22 August 2014, in final form 18 December 2014)
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 asso-
ciated 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 ow 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.
1. Introduction
Tropical cyclones (TCs) undergoing extratropical tran-
sition (ET), a change from a warm-core, axisymmetric
system to a cold-core, asymmet ric 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). 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,
Publisher’s Note: This article was revised on 10 June 2015 in order
to include an updated acknowledgements section.
* Current affiliation: NOAA/OAR Climate Program Office,
Modeling, Analysis, Predictions and Projections Program, Silver
Spring, Maryland.
Corresponding author address: Heather M. Archambault, 1315
East–West Hwy., Silver Spring, MD 20910.
E-mail: heather.archambault@noaa.gov
1122 MONTHLY WEATHER REVIEW VOLUME 143
DOI: 10.1175/MWR-D-14-00270.1
Ó 2015 American Meteorological Society

2005; Riemer et al. 2008; Riemer and Jones 2010; Cordeira
2011; Grams et al. 2013a; Archambault et al. 2013).
Ridge amplification and jet streak intensification are
enhanced by diabatic heating associated with the recurv-
ing TC (e.g., Atallah and Bosart 2003) and attendant
frontogenesis in its northeast quadrant (e.g., Torn 2010).
Above the level of maximum diabatic heating associated
with clouds and precipitation, PV is reduced in conjunc-
tion with diabatic vertical redistribution. In addition, the
divergent outflow generated by diabatic heating advects
low PV toward the PV gradient/jet stream (Archambault
et al. 2013, their Fig. 4).
Given a strong, continuous meridional PV gradient
(i.e., waveguide; Martius et al. 2010), ridge amplification
and jet streak intensification will excite or amplify a baro-
clinic Rossby wave train (RWT) that disperses eddy
kinetic energy downstream while initia ting surfa ce cy-
clogenesis downstream (e.g., Riemer et al. 2 008; Harr
and Dea 2009; Keller et al. 2014). Thus, a recurving TC
may indirectly reconfigure the extratropical flow pattern
and influence the sensible weather thousands of kilome-
ters 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 fol-
lowing 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),theirFig.1;Harr and Archambault (2014)], to
a strengthened jet stream without substantial flow amplifi-
cation [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)]. Anticipating the
extratropical flow response to TC recurvature is crucial
given that flow amplification downstream of a recurving
TC may induce extreme weather (e.g., Cordeira and
Bosart 2010; Grams et al. 2011; Chaboureau et al. 2012;
Pantillon et al. 2014) and contribute to reduced mid-
latitude predictability (e.g., Harr et al. 2008; Anwender
et al. 2008; Reynolds et al. 2009; Keller et al. 2011;
Pantillon et al. 2013, 2014; Harr and Archambault 2015).
The primary factors influencing the downstream flow
response to TC recurvature are (i) the large-scale flow
pattern into which the TC is moving (e.g., Harr and Dea
2009; Riemer et al. 2008; Riemer and Jones 2010,
2014),
and (ii) the interaction between the TC and an extra-
tropical disturbance such as a trough or jet streak (e.g.,
Klein et al. 2002; Ritchie and Elsberry 2007; Riemer and
Jones 2010, 2014; Grams et al. 2013b; Keller et al. 2014).
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).
The large-scale extratropical flow pattern into which
a TC recurves varies by time of year and by ocean basin.
Compared with August–November, June and July are
relatively unfavorable for the North Pacific flow pattern to
become significantly amplified following WNP TC re-
curvature (Archambault et al. 2013,theirFig.15),con-
sistent with the tendency for the North Pacific waveguide/
jet stream to be relatively weak in June and July com-
pared with August–November. A compositing study by
Quinting and Jones (2014) indicates that, whereas RWT
activity is significantly above average following WNP TC
recurvature, it is not significantly above average following
North Atlantic TC recurvature. Based on case studies
(e.g., Grams et al. 2011; Pantillon et al. 2013, 2014), anti-
cyclonic Rossby wave breaking instead of Rossby wave
dispersionmaybemoretypicalfollowingNorthAtlantic
TC recurvature, perhaps owing to the climatologically
short and weak waveguide/jet stream over the North At-
lantic compared with over the North Pacific.
The large-scale extratropical flow response to TC
recurvature also depends on the interaction of the TC
with disturbances in the extratropical flow. The TC–
extratropical flow interaction, or phasing, can be con-
sidered favorable or unfavorable. An example of an
unfavorable phasing between the TC and extratropical
flow is the recurvature of WNP TC Jangmi (2008). As
the TC recurved into the base of a WNP trough, the jet
stream was enhanced downstream but Rossby wave
amplification and dispersion did not occur (Grams et al.
2013a,b). Through numerical modeling experiments,
Grams et al. (2013a) demonstrate that had TC Jangmi
recurved ahead of the trough rather than into the base of
the trough, a high-amplitude RWT likely would have
been induced. They find that the shift in TC position
required to discriminate between RWT and no-RWT
scenarios is only 130 km, which they note is the average
48-h TC position error for ensemble mean ECMWF
forecasts (Lang et al. 2012).
In a recent climatological study (Archambault et al.
2013), the top quintile of TC–extratropical interactions,
defined by the magnitude of negative PV advection by
the irrotational wind associated with the recurving TC, is
found to be associated with a sustained, highly statisti-
cally significant amplification of the North Pacific flow.
In contrast, the bottom quintile of TC–extratropical flow
interactions is found to be associated with a shorter-
lived, less statistically significant amplification of the
North Pacific flow. In the present study, the climato-
logical study of Archambault et al. (2013) is used as the
basis for a comprehensive composite analysis of the
extratropical flow response to WNP TC recurvature. In
particular, key synoptic–dynamic differences are illus-
trated between strong and weak TC–extratropical flow
APRIL 2015 A R C H A M B A U L T E T A L . 1123

interactions, which are important to understanding dif-
ferences in the downstream extratropical flow response
to TC recurvature.
The remainder of this paper is organized as follows.
Section 2 describes the methodology. Section 3 presents
composite analyses of the midlatitude flow response to
recurving WNP TCs and compares composite analyses
of strong and weak TC–extratropical flow interactions
during WNP TC recurvature. Section 4 provides a dis-
cussion, and section 5 contains a summary and an
overview of future work.
2. Methodology
a. Recurvature-relative compositing methodology
To examine the extratropical flow response to recurv-
ing WNP TCs, all 292 recurving WNP TCs identified
during 1979–2009 from the Japan Meteorological Agency
best track dataset by Archambault et al. (2013) are com-
posited. Tropical cyclone recurvature is defined following
Archambault et al. (2013) as a change in TC heading from
westward to eastward as a TC moves poleward. The re-
curvature point corresponds to the most westward posi-
tion of the recurving TC. All recurving TCs are required
to be at tropical storm intensity or greater at the time of
recurvature (i.e., T 1 0 h), and to eventually become ex-
tratropical (i.e., complete ET). The recurving TCs mainly
occur during May–December, with a peak in activity
during August–October. September has the highest in-
cidence of TC recurvature of any month, with 82 cases
identified in 31 years, a frequency of 2.6 yr
21
.
Composite analyses of the recurving WNP TCs are
constructed in a recurvature-relative framework. That is,
fields for each case are shifted such that the recurvature
point is collocated with the mean recurvature point at the
time of recurvature (T 1 0 h). As illustrated by a compar-
ison of conventional geography-relative and recurvature-
relative TC tracks (Figs. 1a,b), the recurvature-relative
framework reduces composite smearing that would arise
from the spatial variability of the recurving TC tracks
(Fig. 1a). The track variability partially reflects the in-
fluence of the time of year: Between May and August, TC
recurvature shifts poleward as the North Pacific jet stream
weakens and shifts poleward, and thereafter shifts equa-
torward through December as the jet stream strengthens
and shifts equatorward (e.g., Archambault et al. 2013,
section 3e).
The 6-hourly 2.58 NCEP–NCAR reanalysis fields
(Kalnay et al. 1996; Kistler et al. 2001)areusedtocon-
struct the composite analyses. Although higher-resolution
reanalyses such as the 0.58 Climate Forecast System Re-
analysis (Saha et al. 2010) are available, the NCEP–NCAR
reanalysis is used for consistency with the Archambault
et al. (2013) climatology. As discussed in Archambault
et al. (2013, their section 2d), the 2.58 NCEP–NCAR re-
analysis is able to capture synoptic signatures of TC–
ext ratropical flow interactions.
The statistical significance of the composite fields with
respect to climatology is assessed using a two-sided
Student’s t test (e.g., Wilks 2006, see section 5.2.1).
The climatology is produced from 1979–2009 21-day
running means of recurvature-relative 2.58 NCEP–
NCAR reanalysis fields.
b. Interaction-relative compositing methodology
Composite analysis is used to compare the extratropical
flow response to strong and weak TC–extratropical
FIG. 1. Recurving WNP TC tracks (2000–09 only; N 5 101) for T 2
48 to T 1 72 h plotted in (a) geography-relative and (b) recurvature-
relative frameworks. The thick black curve denotes the composite
track of all recurving TCs (N 5 292) for T 2 48 to T 1 72 h. The TC
symbol denotes the composite recurvature point (24.98N, 134.08E) for
all recurving TCs.
1124 MONTHLY WEATHER REVIEW VOLUME 143

flow interactions during WNP TC recurvature. For each
recurving TC, the strength of the interaction (i.e., the
interaction metric) is defined as the magnitude of the
spatially and temporally averaged 250–150-hPa layer-
averaged PV advection by the irrotational wind associ-
ated with the TC computed from 6-hourly 2.58 NCEP–
NCAR reanalysis (Archambault et al. 2013, their section
2d). The spatial (1583158) and temporal (48 h) averaging
is centered on the point and time (i.e., T 1 0 h), re-
spectively, of maximum interaction, which is defined as
the highest instantaneous magnitude of negative PV ad-
vection by the irrotational wind associated with the TC.
As noted by Archambault et al. (2013, their Fig. 5a) for
the case of WNP TC Oscar (1995) and by Cordeira (2011,
p. 111) for the case of WNP TC Dale (1996), the region
of strongest negative PV advection by the irrotational
wind generally tends to be closely aligned with the up-
stream edge of the TC cirrus shield. A point of maximum
interaction is not identified for 20 of the 292 recurving TC
cases because the negative PV advection by the irrotational
wind associated with the TC never exceeds an arbitrary
threshold of 1 PVU day
21
(1 PVU 5 10
6
Kkg
21
m
2
s
21
).
These cases are considered no-interaction cases. For the
remaining 272 recurving TC cases, those associated with an
interaction metric in the top quintile are categorized as
strong interactions (N 5 54), whereas those associated with
an interaction in the bottom quintile are categorized as
weak interactions (N 5 54).
As discussed in Archambault et al. (2013, their section
2d), the negative PV advection by the irrotational wind is
useful for diagnosing the strength of the TC–extratropical
flow interaction because divergent outflow impinging
upon the PV waveguide/jet stream is a key signature of
Rossby wave amplification induced by a TC (e.g., Harr
et al. 2008; Riemer et al. 2008; Hodyss and Hendricks
2010; Pantillon et al. 2013, 2014; Grams et al. 2013a,b).
Ridge amplification and jet streak intens ification
occur in conjunction with Rossby wave amplification
as the divergent outflow of the TC deforms PV con-
tours poleward and strengthens the PV gradient
(Archambault et al. 2013, their Fig. 4). T he effect s of
diabatic heating are included in this framework, as
upper-level low-PV air that arises from diabatic
heating is advected by diabatically driven divergent
outflow toward the waveguide/jet stream.
To examine strong and weak TC–extratropical flow
interactions, composites are constructed such that they
are centered on the point of maximum TC–extratropical
flow interaction. This ‘‘interaction-r elative’’ framework
is used to maximize the sharpness of the composite
synoptic features associated with the TC–extratropical
flow interactions. To construct these composites, the 2.58
NCEP–NCAR fields for a given case are shifted such
that the point of maxi mum TC–e xtratro pical flow in-
teraction is collocated with the mean point of maxi-
mum interaction (Fig. 2). The statistical significance of
the composite fields with respect to climatology is
evaluated using a two-sided Student’s t test. The cli-
matology is produced from 1979–2009 21-day running
means of interacti ve-r elative 2.58 NCEP–NCAR re-
analysis fields.
For all WNP TCs undergoing recurvature, the point of
maximum interaction tends to be located approximately
68–148N of the TC center (Fig. 2). However, for strong
interaction cases the location of the mean point of
maximum interaction is significantly farther northward
(11.68 vs 8.18 latitude) and westward (21.18 vs 1.58 lon-
gitude) relative to the TC compared with weak in-
teraction cases (Fig. 2; Table 1).
The synoptic signatures and dynamics of strong and
weak TC–extratropical flow interactions are compared
using a variety of plan-view composite analyses pro-
duced at the time of maximum interaction (i.e., T 1 0 h).
The irrotational and nondivergent wind fields are com-
puted for each individual case prior to compositing. All
derived variables, including PV advection, Q vectors,
and Q-vector divergence (described subsequently in
section 2d), and PV frontogenesis
1
[i.e., the rate of
change of the magnitude of the horizontal PV gradi-
ent; e. g., Davies and Rossa (1998), Cordeira (2011,
p. 105)], are computed on isobaric l evels from the
composite fields.
c. Assessment of characteristic magnitudes of various
quantities for composite cases
Although useful for identifying common synoptic fea-
tures, composite analyses have limited utility in de-
termining the characteristic magnitudes of these features
(e.g., Archambault et al. 2008). To compensate for this
limitation, the maximum values of various quantities for
the individual cases that constitute the composites are
analyzed for strong and weak TC–extratropical flow in-
teractions. For each case, the maximum magnitude of
a given quantity in the NCEP–NCAR reanalysis is ob-
tained by searching within a 208 latitude 3 208 longitude
box centered on the point of maximum interaction.
Whether the mean of the maximum magnitude of a given
quantity is significantly different for strong versus weak
interactions is tested using a nonparametric two-sided
Wilcoxon–Mann–Whitney rank-sum test (e.g., Wilks
2006, section 5.3.1).
1
The PV frontogenesis is calculated by replacing potential
temperature with PV in the simplified 2D form of the Miller (1948)
frontogenesis equation [e.g., Novak et al. 2004, their Eq. (1)].
A
PRIL 2015 A R C H A M B A U L T E T A L . 1125

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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)....

    [...]

  • ...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....

    [...]

  • ...…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…...

    [...]

  • ...…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)....

    [...]

  • ...…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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Abstract: The dynamical mechanisms that led to downstream ridging during the extratropical transition (ET) of Typhoons Tokage and Nabi are evaluated using data drawn from a cycling ensemble Kalman filter coupled with the Weather Research and Forecasting Model (WRF). During both transitions, the ensemble covariances indicate that the 350-K potential vorticity (PV) at the apex of the ridge, which is used to define the ridge structure, is proportional to the amount of precipitation along the baroclinic zone to the northeast of the tropical cyclone (TC), and at some times to the upper-tropospheric divergence above the tropical cyclone. Multivariate regression calculations indicate that the frontal precipitation has the largest impact on the ridge amplitude and area during Tokage’s transition, while the TC divergence has roughly equal impact during some times of Nabi’s transition. The amount of precipitation along the baroclinic zone is modulated by the lower-tropospheric frontogenesis and moisture flux on the ...

50 citations


"A Composite Perspective of the Extr..." refers background in this paper

  • ...1 2015 American Meteorological Society Ridge amplification and jet streak intensification are enhanced by diabatic heating associated with the recurving TC (e.g., Atallah and Bosart 2003) and attendant frontogenesis in its northeast quadrant (e.g., Torn 2010)....

    [...]

  • ...…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…...

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  • ...2014), whether associated with recurving TCs (e.g., Henderson et al. 1999; Torn 2010), mesoscale convective systems (e....

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Journal ArticleDOI
TL;DR: The characteristics of the extratropical transition (ET) of tropical cyclones and its impact on the midlatitude flow are examined in the THORPEX Interactive Grand Global Ensemble (TIGGE) multimodel ensemble prediction system (EPS) as mentioned in this paper.
Abstract: [1] The characteristics of the extratropical transition (ET) of tropical cyclones and its impact on the midlatitude flow are examined in the THORPEX Interactive Grand Global Ensemble (TIGGE) multimodel ensemble prediction system (EPS). Ten ensemble forecasts initialized prior to ET for five tropical cyclones in 2008 are investigated using an empirical orthogonal function analysis and fuzzy clustering methodology. Each forecast contains 231 members from eight different global EPS. The EPS contributing to TIGGE differ in their spread and their contributions to the different scenarios. Some of the individual EPS are generally confined to only a few scenarios, whereas others contribute regularly to almost all. TIGGE contains more development scenarios than European Centre for Medium Range Weather Forecast (ECMWF) EPS but the full range of development scenarios is only found with the ECMWF included in the multimodel EPS.

49 citations


"A Composite Perspective of the Extr..." refers background in this paper

  • ...…(e.g., Cordeira and Bosart 2010; Grams et al. 2011; Chaboureau et al. 2012; Pantillon et al. 2014) and contribute to reduced midlatitude predictability (e.g., Harr et al. 2008; Anwender et al. 2008; Reynolds et al. 2009; Keller et al. 2011; Pantillon et al. 2013, 2014; Harr andArchambault 2015)....

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Journal ArticleDOI
TL;DR: Singular vectors (SVs) are used to study the sensitivity of 2-day forecasts of recurving tropical cyclones in the western North Pacific to changes in the initial state as mentioned in this paper.
Abstract: Singular vectors (SVs) are used to study the sensitivity of 2-day forecasts of recurving tropical cyclones (TCs) in the western North Pacific to changes in the initial state The SVs are calculated using the tangent and adjoint models of the Navy Operational Global Atmospheric Prediction System (NOGAPS) for 72 forecasts for 18 TCs in the western North Pacific during 2006 In addition to the linear SV calculation, nonlinear perturbation experiments are also performed in order to examine 1) the similarity between nonlinear and linear perturbation growth and 2) the downstream impacts over the North Pacific and North America that result from changes to the 2-day TC forecast Both nonrecurving and recurving 2-day storm forecasts are sensitive to changes in the initial state in the near-storm environment (in an annulus approximately 500 km from the storm center) During recurvature, sensitivity develops to the northwest of the storm, usually associated with a trough moving in from the west These upstr

47 citations


"A Composite Perspective of the Extr..." refers background in this paper

  • ...…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. 2009; Anwender et al. 2010; Grams et al. 2013b), and idealized modeling studies (e.g., Riemer et al. 2008; Riemer and Jones 2010)…...

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  • ...2013), case studies (e.g., Harr and Dea 2009; Reynolds et al. 2009; Anwender et al. 2010; Grams et al. 2013b), and idealized modeling...

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  • ...…(e.g., Cordeira and Bosart 2010; Grams et al. 2011; Chaboureau et al. 2012; Pantillon et al. 2014) and contribute to reduced midlatitude predictability (e.g., Harr et al. 2008; Anwender et al. 2008; Reynolds et al. 2009; Keller et al. 2011; Pantillon et al. 2013, 2014; Harr andArchambault 2015)....

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Journal ArticleDOI
TL;DR: In this article, the dominant vertical structures for analysis and forecast errors are estimated in midlatitudes using a small ensemble of operational analyses, and the results for fixed locations in the central North Pacific and eastern North America are compared with results for zonal wavenumber 9, which provides a representative sample of baroclinic waves.
Abstract: The dominant vertical structures for analysis and forecast errors are estimated in midlatitudes using a small ensemble of operational analyses. Errors for fixed locations in the central North Pacific and eastern North America are selected for comparing errors in regions with relatively low and high observation density, respectively. Results for these fixed locations are compared with results for zonal wavenumber 9, which provides a representative sample of baroclinic waves. This study focuses on deviations from the ensemble mean for meridional wind and temperature at 40°N; these quantities are chosen for simplicity and because they capture dynamical and thermodynamical aspects of midlatitude baroclinic waves. Results for the meridional wind show that analysis and forecast errors share the same dominant vertical structure as the analyses. This structure peaks near the tropopause and decays smoothly toward small values in the middle and lower troposphere. The dominant vertical structure for analysi...

45 citations


"A Composite Perspective of the Extr..." refers background in this paper

  • ...…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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Journal ArticleDOI
TL;DR: In this paper, the extratropical transition (ET) of tropical cyclone Lili (1996) in the North Atlantic resulted in a moderate extarropical development of a baroclinic cyclone.
Abstract: The transition that a tropical cyclone experiences as it moves into the extratropical environment (known as extratropical transition) can result in the decay or intensification of a baroclinic cyclone. The extratropical transition (ET) of Tropical Cyclone Lili (1996) in the North Atlantic resulted in a moderate extratropical development of a baroclinic cyclone. The impact of Lili in the extratropical development that occurred during its ET is investigated. Numerical experiments are performed using potential vorticity inversion and the Met Office Unified Model to forecast the extratropical development with and without the tropical cyclone in the initial conditions. In contrast with other case studies in the literature, Lili is shown to play a crucial role during its ET in the development of a baroclinic cyclone that occurred in the same region. A hypothesis of the possible scenarios of ET is presented that links the case-to-case variability of ET case studies in the literature with a classificatio...

45 citations


"A Composite Perspective of the Extr..." refers background or methods in this paper

  • ...In addition, the divergent outflow generated by diabatic heating advects low PV toward the PV gradient/jet stream (Archambault et al. 2013, their Fig. 4). Given a strong, continuous meridional PV gradient (i.e., waveguide; Martius et al. 2010), ridge amplification and jet streak intensification will excite or amplify a baroclinic Rossby wave train (RWT) that disperses eddy kinetic energy downstream while initiating surface cyclogenesis downstream (e.g., Riemer et al. 2008; Harr and Dea 2009; Keller et al. 2014). 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 recurvaturemay range from amarked flow amplification [e.g., with TC Oscar (1995); Archambault et al. (2013), their Fig....

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  • ...In addition, the divergent outflow generated by diabatic heating advects low PV toward the PV gradient/jet stream (Archambault et al. 2013, their Fig. 4). Given a strong, continuous meridional PV gradient (i.e., waveguide; Martius et al. 2010), ridge amplification and jet streak intensification will excite or amplify a baroclinic Rossby wave train (RWT) that disperses eddy kinetic energy downstream while initiating surface cyclogenesis downstream (e.g., Riemer et al. 2008; Harr and Dea 2009; Keller et al. 2014). 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 recurvaturemay range from amarked flow amplification [e.g., with TC Oscar (1995); Archambault et al. (2013), their Fig. 1;Harr andArchambault (2014)], to a strengthened jet stream without substantial flow amplification [e.g., with TC Jangmi (2008); Grams et al....

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  • ...Compared with August–November, June and July are relatively unfavorable for the North Pacific flow pattern to become significantly amplified following WNP TC recurvature (Archambault et al. 2013, their Fig. 15), consistent with the tendency for the North Pacific waveguide/jet stream to be relatively weak in June and July compared with August–November. A compositing study by Quinting and Jones (2014) indicates that, whereas RWT activity is significantly above average following WNP TC recurvature, it is not significantly above average followingNorthAtlantic TC recurvature. Based on case studies (e.g., Grams et al. 2011; Pantillon et al. 2013, 2014), anticyclonic Rossby wave breaking instead of Rossby wave dispersion may be more typical followingNorthAtlantic TC recurvature, perhaps owing to the climatologically short and weak waveguide/jet stream over the North Atlantic compared with over the North Pacific. The large-scale extratropical flow response to TC recurvature also depends on the interaction of the TC with disturbances in the extratropical flow. The TC– extratropical flow interaction, or phasing, can be considered favorable or unfavorable. An example of an unfavorable phasing between the TC and extratropical flow is the recurvature of WNP TC Jangmi (2008). As the TC recurved into the base of a WNP trough, the jet stream was enhanced downstream but Rossby wave amplification and dispersion did not occur (Grams et al....

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  • ...In addition, the divergent outflow generated by diabatic heating advects low PV toward the PV gradient/jet stream (Archambault et al. 2013, their Fig. 4). Given a strong, continuous meridional PV gradient (i.e., waveguide; Martius et al. 2010), ridge amplification and jet streak intensification will excite or amplify a baroclinic Rossby wave train (RWT) that disperses eddy kinetic energy downstream while initiating surface cyclogenesis downstream (e.g., Riemer et al. 2008; Harr and Dea 2009; Keller et al. 2014). 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 recurvaturemay range from amarked flow amplification [e.g., with TC Oscar (1995); Archambault et al. (2013), their Fig. 1;Harr andArchambault (2014)], to a strengthened jet stream without substantial flow amplification [e....

    [...]

  • ...Compared with August–November, June and July are relatively unfavorable for the North Pacific flow pattern to become significantly amplified following WNP TC recurvature (Archambault et al. 2013, their Fig. 15), consistent with the tendency for the North Pacific waveguide/jet stream to be relatively weak in June and July compared with August–November. A compositing study by Quinting and Jones (2014) indicates that, whereas RWT activity is significantly above average following WNP TC recurvature, it is not significantly above average followingNorthAtlantic TC recurvature. Based on case studies (e.g., Grams et al. 2011; Pantillon et al. 2013, 2014), anticyclonic Rossby wave breaking instead of Rossby wave dispersion may be more typical followingNorthAtlantic TC recurvature, perhaps owing to the climatologically short and weak waveguide/jet stream over the North Atlantic compared with over the North Pacific. The large-scale extratropical flow response to TC recurvature also depends on the interaction of the TC with disturbances in the extratropical flow. The TC– extratropical flow interaction, or phasing, can be considered favorable or unfavorable. An example of an unfavorable phasing between the TC and extratropical flow is the recurvature of WNP TC Jangmi (2008). As the TC recurved into the base of a WNP trough, the jet stream was enhanced downstream but Rossby wave amplification and dispersion did not occur (Grams et al. 2013a,b). Through numerical modeling experiments, Grams et al. (2013a) demonstrate that had TC Jangmi recurved ahead of the trough rather than into the base of the trough, a high-amplitude RWT likely would have been induced....

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Frequently Asked Questions (2)
Q1. What are the contributions mentioned in the paper "A composite perspective of the extratropical flow response to recurving western north pacific tropical cyclones" ?

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 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 ).