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George H. Bryan, Jason C. Knievel, and Matthew D. Parker

’s relevance to squall-line properties that is based on a model other than that used by RKW88 and WR04 . Therefore, the main goal of our study is to assess whether RKW theory’s relevance to squall lines is supported by other numerical models. We base our new simulations on the recent study by WR04 , using the same simulation details and analysis techniques. We use three additional numerical models, all of which have been developed more recently than the model used by WR04 . Our findings provide

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Dominik Jacques, Daniel Michelson, Jean-François Caron, and Luc Fillion

the Rapid Refresh (RAP) and the High-Resolution Rapid Refresh (HRRR), latent heating is prescribed by 3D reflectivity observations at the beginning of forecasts ( Weygandt and Benjamin 2007 ; Weygandt et al. 2008 ; Alexander et al. 2017 ). Of all diabatic initialization techniques, latent heat nudging (LHN; Wang and Warner 1988 ; Manobianco et al. 1994 ; Jones and Macpherson 1997 ) is probably the most popular method for assimilating radar reflectivity in operational systems. It has been used

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Bo Liu, Boujemaa Ait-El-Fquih, and Ibrahim Hoteit

are updated as in the KF and their weights are updated as in the PF. Two families of GM-based algorithms can be distinguished by how the forecast GM approximation is constructed: Clustering-based GM algorithms— In this class of algorithms, clustering techniques are used to build a GM representation of the forecast pdf from a forecast ensemble. When a new observation is available, the weights are first updated according to the PF. The particles are then resampled before applying the Kalman update

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Reto Stauffer, Nikolaus Umlauf, Jakob W. Messner, Georg J. Mayr, and Achim Zeileis

exceeds threshold κ [Eq. (A6) ], and the binary observation which takes 0 for all observations and 1 otherwise. Correspondingly, the Brier skill score is defined as REFERENCES Ben Bouallègue , Z. , and S. E. Theis , 2014 : Spatial techniques applied to precipitation ensemble forecasts: From verification results to probabilistic products . Meteor. Appl. , 21 , 922 – 929 , doi: 10.1002/met.1435 . 10.1002/met.1435 Box , G. E. P. , and D. R. Cox , 1964 : An analysis of

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Aaron Donohoe and David S. Battisti

a skew-normal distribution to the Eulerian data in section 4 , and we show that the cyclone/anticyclone asymmetry makes only a minor contribution to the time-mean field in the storm-track regions. A summary and discussion follow. 2. Data, techniques, and filter properties The data used in this study are 6-hourly sea level pressure data from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40; Uppala et al. 2005 ) at a horizontal resolution of T62. 1 We

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Andrew W. Robertson, Nicolas Vigaud, Jing Yuan, and Michael K. Tippett

1. Introduction Subseasonal to Seasonal (S2S) forecasting at lead times of about 10–100 days has garnered much recent attention due to advances in dynamical model skill at predicting the Madden–Julian oscillation (MJO; Vitart 2014 ; Kim et al. 2018 ) and through the construction of new multimodel databases of subseasonal forecasts and reforecasts ( Vitart et al. 2017 ; Pegion et al. 2019 ). However, the degree of useful forecast skill is still unclear in the extratropics where weather and

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Paul J. Roebber

Training Workshop on the Interpretation of NWP Products in Terms of Local Weather Phenomena and Their Verification, Wageningen, Netherlands, WMO, WMO PSMP Rep. Series 34, XX-27–XX-32 . Raftery , A. E. , T. Gneiting , F. Balabdaoui , and M. Polakowski , 2005 : Using Bayesian model averaging to calibrate forecast ensembles . Mon. Wea. Rev. , 133 , 1155 – 1174 , doi: 10.1175/MWR2906.1 . Roebber , P. J. , 1998 : The regime dependence of degree day forecast technique, skill, and value

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Nusret Balci, Anna L. Mazzucato, Juan M. Restrepo, and George R. Sell

multiplicative ergodic theorem (MET) and the finite-time singular vectors to approximate the Lyapunov vectors. The BV algorithm is a finite-time, forward sensitivity methodology that, in addition to being useful in characterizing model sensitivity to initial conditions, has been proposed as a means to produce a reduced-rank representation of the background error in data assimilation and forecast error-covariance approximations (see, e.g., Corazza et al. (2003) . Several articles in the literature have

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Ruiqiang Ding, Jianping Li, and Kyong-Hwan Seo

tropical and extratropical circulation anomalies, it is of great interest to investigate its upper limit of predictability. For example, information on the MJO predictability limit could be used as a basic guideline for the future improvement of forecast models. However, the limit of the predictability of the MJO phenomenon remains an open issue. A number of recent studies have demonstrated that the useful skill of the MJO in existing numerical and statistical models can reach about 15–20 days (e

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Thorsten Simon, Peter Fabsic, Georg J. Mayr, Nikolaus Umlauf, and Achim Zeileis

technique can be found in Mayr et al. (2012) . However, selecting the right-sized subset of covariates ( Meinshausen and Bühlmann 2010 )—that is, avoiding selecting some noise variables ( Hofner et al. 2015 )—remains challenging. A solution to this issue is combining gradient boosting as a method of regularization with stability selection ( Hofner et al. 2015 ). The aim of this study is to develop a probabilistic forecasting method for the occurrence of thunderstorms in the eastern Alps and their

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