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Jana Čampa and Heini Wernli

, heat content, and precipitable water in North Atlantic cyclones. Mass and Dotson (2010) considered the structure of the strongest cyclones in the northwestern United States. They found the strongest winds southeast of the cyclones and interestingly a cold temperature anomaly at 850 hPa in the center. A bent-back warm front was found to be a typical feature of these storms. Considering the structure of extratropical cyclones is also an important aspect when evaluating climate model simulations

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Maxi Boettcher and Heini Wernli

1. Introduction Meteorological research on diabatic Rossby waves (DRWs) has been intensifying in recent years after a DRW was detected for the first time in numerical weather prediction (NWP) model output for a high-impact weather event. According to a mesoscale model hindcast simulation, a DRW served as an important precursor to the “Lothar” storm after Christmas 1999, which was one of the most harmful winter storms over Europe in the last few decades ( Wernli et al. 2002 ). The explosive

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Simon T. K. Lang, Sarah C. Jones, Martin Leutbecher, Melinda S. Peng, and Carolyn A. Reynolds

the strong gradients associated with such an intense system. In this study we investigate the sensitivity of SVs with respect to different modeling configurations in order to evaluate the dynamical relevance of SVs computed in one configuration but applied to another. For ensemble forecasts as well as for observation targeting, the actual analysis uncertainty is also relevant [ Barkmeijer et al. 1998 , 1999 ; Reynolds et al. 2007 ; Lawrence et al. 2009 ; see Berliner et al. (1999) for a

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Andrea Schneidereit, Silke Schubert, Pavel Vargin, Frank Lunkeit, Xiuhua Zhu, Dieter H. W. Peters, and Klaus Fraedrich

train. As this wave train is apparent throughout the troposphere ( Orsolini and Nikulin 2006 ), the large-scale flow seems to play an important role in European heat waves. Model simulations indicate that the anomalous circulation during the summer of 2010 over eastern Europe can be ascribed primarily to natural internal atmospheric variability rather than to climate change or ocean boundary conditions like sea surface temperature or sea ice extent ( Dole et al. 2011 ), reflecting changes in the

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Julian F. Quinting and Sarah C. Jones

. Meteor. Soc. , 128 , 93 – 117 , doi: 10.1256/00359000260498806 . Evans , J. L. , and R. E. Hart , 2003 : Objective indicators of the life cycle evolution of extratropical transition for Atlantic tropical cyclones . Mon. Wea. Rev. , 131 , 909 – 925 , doi: 10.1175/1520-0493(2003)131<0909:OIOTLC>2.0.CO;2 . Evans , J. L. , J. M. Arnott , and F. Chiaromonte , 2006 : Evaluation of operational model cyclone structure forecasts during extratropical transition . Mon. Wea. Rev. , 134

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

; moreover, the forecast became rather poor after a lead time of as little as 5 days. The latter result seems to be at odds with the commonly held view that large-scale phenomena such as RWPs should be predictable on a rather long time scale. However, this evaluation was for a single case only involving a single forecast model; further systematic studies are required to possibly generalize these results. Regarding the waveguide, several operational forecast models are fraught with a spurious decrease of

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Andrea Schneidereit, Dieter H. W. Peters, Christian M. Grams, Julian F. Quinting, Julia H. Keller, Gabriel Wolf, Franziska Teubler, Michael Riemer, and Olivia Martius

( Tripathi et al. 2015 ). Matsuno (1971) developed a dynamical model of the stratospheric sudden warming phenomena in which tropospheric forced planetary wave packets propagate upward into the stratosphere. The deposition of their easterly angular momentum [Eliassen–Palm flux (EP flux) convergence] leads to a weakening and breakdown of the polar night jet. Several processes influence the occurrence of MSSW events in the Northern Hemisphere: the quasi-biennial oscillation (QBO) and the solar cycle (e

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Yannick Barton, Paraskevi Giannakaki, Harald von Waldow, Clément Chevalier, Stephan Pfahl, and Olivia Martius

temporal dependence of precipitation and other extremes is of interest for insurance companies as their loss models are typically based on independence assumptions. In this study, we focus on the temporal clustering of extreme regional-scale precipitation events in southern Switzerland that are, among other high impacts, relevant for the flooding of Lago Maggiore. A number of studies have analyzed the statistical properties of the temporal clustering of extreme events, namely European winter storms (e

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Gabriel Wolf and Volkmar Wirth

appropriate in the current context is the wave activity flux of Takaya and Nakamura (2001) . One particular feature of this formulation is its phase independence; this means that it discounts individual troughs and ridges and focuses on the dynamics of the entire wave packet instead ( Danielson et al. 2006 ). Focus on the entire wave packet is desirable, for instance, when studying model errors as opposed to initial condition errors ( Gray et al. 2014 ), and it would be interesting to find out whether

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Olivia Martius and Heini Wernli

of the extratropical trajectories on the angular momentum budget can again be evaluated semiquantitatively from the trajectory analysis. The total Eulerian angular momentum change of the subtropical jet over Africa for the time period between 0600 UTC 7 January and 0000 UTC 9 January amounted to 4 × 10 11 s −1 . This number can be compared to the total change of angular momentum change along the trajectories for different time intervals prior to reaching the jet. The mean accumulated angular

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