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cyclone constitutes an external forcing with persistent structure to the midlatitude wave. This idea is in marked contrast to traditional initial-value studies of baroclinic development, in which the initial perturbations are embedded in the midlatitude flow and are thus not an external forcing (e.g., Simmons and Hoskins 1979 ; Hakim 2000 ). 2) Evolution of the upstream trough ET may also influence the upstream trough, which may experience modifications of its shape, meridional extension, and
cyclone constitutes an external forcing with persistent structure to the midlatitude wave. This idea is in marked contrast to traditional initial-value studies of baroclinic development, in which the initial perturbations are embedded in the midlatitude flow and are thus not an external forcing (e.g., Simmons and Hoskins 1979 ; Hakim 2000 ). 2) Evolution of the upstream trough ET may also influence the upstream trough, which may experience modifications of its shape, meridional extension, and
.g., Dritschel and McIntyre 2008 ). A strong gradient of potential vorticity, in turn, represents a strong restoring force for parcels away from its unperturbed trajectory, which guarantees close to linear wave behavior. The jet in this context is considered to be part of the background flow, and to the extent that the jet makes some gentle excursions in the meridional direction, the RWP follows these excursions on its otherwise zonal and eastward trajectory. Anomalies due to the RWPs are measured with
.g., Dritschel and McIntyre 2008 ). A strong gradient of potential vorticity, in turn, represents a strong restoring force for parcels away from its unperturbed trajectory, which guarantees close to linear wave behavior. The jet in this context is considered to be part of the background flow, and to the extent that the jet makes some gentle excursions in the meridional direction, the RWP follows these excursions on its otherwise zonal and eastward trajectory. Anomalies due to the RWPs are measured with
-based short-range QPF evaluation over Switzerland . Meteor. Z. , 17 , 827 – 848 , doi:10.1127/0941-2948/2008/0344 . Johnson, C. , and Swinbank R. , 2009 : Medium-range multimodel ensemble combination and calibration . Quart. J. Roy. Meteor. Soc. , 135A , 777 – 794 , doi:10.1002/qj.383 . Kiladis, G. N. , and Weickmann K. M. , 1992 : Extratropical forcing of tropical Pacific convection during winter . Mon. Wea. Rev. , 120 , 1924 – 1938 . Klein, H. , and Coauthors , 2010 : Saharan
-based short-range QPF evaluation over Switzerland . Meteor. Z. , 17 , 827 – 848 , doi:10.1127/0941-2948/2008/0344 . Johnson, C. , and Swinbank R. , 2009 : Medium-range multimodel ensemble combination and calibration . Quart. J. Roy. Meteor. Soc. , 135A , 777 – 794 , doi:10.1002/qj.383 . Kiladis, G. N. , and Weickmann K. M. , 1992 : Extratropical forcing of tropical Pacific convection during winter . Mon. Wea. Rev. , 120 , 1924 – 1938 . Klein, H. , and Coauthors , 2010 : Saharan
extratropical cyclone, veering away from Choi-Wan and the inherent generation of K e due to baroclinic processes. In these cases, Choi-Wan has only a minor impact on the amplification of the wave train w a . Furthermore, converging energy fluxes from upstream regions suggest a midlatitude forcing in scenario III. If Choi-Wan merges with the frontal wave (scenario II, Fig. 8b ), wave train w a is strongly amplified, due to the downstream dispersion of K e , emanating from the storm, and propagates
extratropical cyclone, veering away from Choi-Wan and the inherent generation of K e due to baroclinic processes. In these cases, Choi-Wan has only a minor impact on the amplification of the wave train w a . Furthermore, converging energy fluxes from upstream regions suggest a midlatitude forcing in scenario III. If Choi-Wan merges with the frontal wave (scenario II, Fig. 8b ), wave train w a is strongly amplified, due to the downstream dispersion of K e , emanating from the storm, and propagates
-0315.1 Moncrieff , M. W. , D. E. Waliser , and J. Caughey , 2012 : Progress and direction in tropical convection research: YOTC International Science Symposium . Bull. Amer. Meteor. Soc. , 93 , ES65 – ES69 , https://doi.org/10.1175/BAMS-D-11-00253.1 . 10.1175/BAMS-D-11-00253.1 Nie , Y. , Y. Zhang , G. Chen , and X.-Q. Yang , 2016 : Delineating the barotropic and baroclinic mechanisms in the midlatitude eddy-driven jet response to lower-tropospheric thermal forcing . J. Atmos. Sci
-0315.1 Moncrieff , M. W. , D. E. Waliser , and J. Caughey , 2012 : Progress and direction in tropical convection research: YOTC International Science Symposium . Bull. Amer. Meteor. Soc. , 93 , ES65 – ES69 , https://doi.org/10.1175/BAMS-D-11-00253.1 . 10.1175/BAMS-D-11-00253.1 Nie , Y. , Y. Zhang , G. Chen , and X.-Q. Yang , 2016 : Delineating the barotropic and baroclinic mechanisms in the midlatitude eddy-driven jet response to lower-tropospheric thermal forcing . J. Atmos. Sci
