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Tobias Selz and George C. Craig

perturbation amplitudes and structures may, however, originate from the boundary layer in an environment with high convective available potential energy (CAPE) and convective inhibition. Here perturbations might be able to trigger additional convective cells instead of just displacing existing ones ( Leoncini et al. 2010 ). Furthermore there is evidence that the upscale impact of convection on the geostrophically balanced flow may also depend strongly on the convective regime (i.e., if the convective

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Martin Weissmann, Florian Harnisch, Chun-Chieh Wu, Po-Hsiung Lin, Yoichiro Ohta, Koji Yamashita, Yeon-Hee Kim, Eun-Hee Jeon, Tetsuo Nakazawa, and Sim Aberson

interpolation ( Wu et al. 2002 ): the background field (the previous 6-h forecast) is combined with observations with a 3D-Var multivariate formalism ( Kleist et al. 2009 ). Dropsonde observations within a radius of 111 km from the typhoon center (or 3 times the specified radius of maximum wind if larger than 111 km) are currently not used in the NCEP analysis ( Aberson 2008 ). c. KMA WRF experiment description One experiment with dropsondes (DROP) and a control run without additional observations (NODROP

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Marlene Baumgart, Michael Riemer, Volkmar Wirth, Franziska Teubler, and Simon T. K. Lang

across the boundary of the integration domain [second term in Eq. (5) ]. Not explicitly included in the barotropic framework of Boer (1984) , the third term in Eq. (5) constitutes an error source due to the divergence of the quasi-horizontal (adiabatic) flow. The remaining terms describe the influence of nonconservative processes (term 4), the boundary contribution due to changes in the integration area (term 5), and the residual (term 6). We evaluate the PV error tendency equation on an

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Hilke S. Lentink, Christian M. Grams, Michael Riemer, and Sarah C. Jones

) and for more details on the computational methods]. The model is set up with a horizontal resolution of 0.025° (about 2.5 km at 35°N) and 57 vertical levels up to 30-km height, with an enhanced vertical resolution in the planetary boundary layer. Shallow convection is parameterized using the mass-flux scheme of Tiedtke (1989) , while middle and high convection are explicitly computed. For all parameterized processes, the default setup of COSMO is used ( Doms et al

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Christian M. Grams and Heather M. Archambault

1. Introduction The large-scale midlatitude flow is dominated by the upper-level jet stream that serves as a waveguide for Rossby waves (e.g., Martius et al. 2010 ). Because their general evolution follows dry dynamics that can be represented at grid scale in numerical weather prediction (NWP) models, Rossby waves may be expected to feature a high degree of predictability ( Grazzini and Vitart 2015 ). However, major forecast uncertainty and error in the midlatitudes in current NWP models have

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Gabriel Wolf and Volkmar Wirth

packet and smoothly decays to smaller values at the boundaries of the wave packet. The carrier wave C oscillates between positive and negative values and varies on a much shorter spatial scale than A . The amplitude A will also be referred to as envelope in the following. The task of envelope reconstruction is tantamount as to find an algorithm that allows one to compute A ( λ ) when υ ( λ ) is given. In the past, meteorologists have used essentially two methods in order to reach this goal

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Julian F. Quinting, Michael M. Bell, Patrick A. Harr, and Sarah C. Jones

of ET. However, instead of completing transformation, Sinlaku reintensified ( Sanabia 2010 ) and regained typhoon intensity on 19 September (Foerster et al. 2013, manuscript submitted to Mon. Wea. Rev. ). At that time, Sinlaku exhibited a partial eyewall around the low-level circulation maximum that is here defined as the low-level center. The focus of the current study is 20 September when Sinlaku approached the primary midlatitude baroclinic zone to enter the final stage of ET. Sinlaku decayed

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Maxi Boettcher and Heini Wernli

probably related to the increased moisture availability in the ocean boundary layer during the warm season. In addition, the two Pacific peaks in June and October can be related to specific regional weather phenomena (see section 4b ). Fig . 3. Monthly number of DRWs during the years 2001–10 in the (a) North Atlantic and (b) North Pacific. The darker segments of the histogram in Fig. 3 mark the DRWs that intensify explosively as meteorological “bombs” with a SLP deepening of at least one Bergeron 2

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Julia H. Keller, Sarah C. Jones, and Patrick A. Harr

tropical cyclone become a boundary feature of a slightly intensifying extratropical cyclone, embedded ahead of the upstream trough. While a clearly identifiable K e maximum is associated with Choi-Wan ( Fig. 9d ), the frontal wave is rather weakly amplified and does not have a clear energy maxima. Because of the weak baroclinicity in the ridge, the generation of K e via baroclinic conversion is only weak during the first days of interaction ( Fig. 9d , 19–21 September 2009) and only minor

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