A Composite Perspective of the Extratropical Flow Response to Recurving Western North Pacific Tropical Cyclones
Author
Archambault, Heather M.
Keyser, Daniel
Bosart, Lance F.
Davis, Christopher A.
Cordeira, Jason M.
Date
2015-04Metadata
Show full item recordAbstract
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–NCARreanalysis 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. ThisRWT
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 upstreamtrough, 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.
Description
The article of record as published may be found at http://dx.doi.org/10.1175/MWR-D-14-00270.1
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